MATERIAL AND METHODS

Transcription

1 Chapter-3 MATERIAL AND METHODS 3.1. Methods of Analysis of Chromium Analysis of Cr(VI) from effluent by volumetric method: Cr(VI) from effluent was analyzed by volumetric method as described by Vogel (Vogel, 1964). 100ml effluent was taken out into stopper bottle with burette. To it 1g potassium iodide and 3ml concentrated hydrochloric acid was added. Bottle was stopper immediately and placed in dark for 5 minutes. In the reaction between potassium iodide and effluent, I 2 was librated. Liberated iodine was titrated against standardized sodium thiosulphate (0.025N). Same procedure was repeated three times and constant burette reading is used for calculations. Standardization of sodium thiosulphate was performed by using standard K 2 Cr 2 O 7. Before preparation of dichromate solution, K 2 Cr 2 O 7 (solid) was dried in an oven at 110 C for 1 hr. and used for preparation of solution g of K 2 Cr 2 O 7 was weight accurately and 100 ml solution was prepared in distilled water. 10ml dichromate solution was prepared out in stopper bottle and above procedure was followed. Calculation: 1N 1000ml Na 2 S 2 O 3 = g Cr(VI) Analysis of Cr(VI) by spectrophotometric method: When concentration of Cr(VI) is very low than volumetric method cannot be used. At very low concentration analysis of Cr(VI) was performed by spectrophotometric method described by Vogel, (Vogel,1964). Colouring reagent used was diphenyl carbazide (DPC) reagent. DPC reagent was prepared from A.R. grade diphenyl carbazide at 1% concentration in A.R. grade acetone. Reagent was placed in amber coloured well stopper bottle. Standard solution of Cr(VI) for analysis was prepared from oven dried A. R, grade potassium dichromate. 100ppm stock solution was prepare in first step (0.0716g K 2 Cr 2 O 7 (molecular weight g) was

2 weighed accurately and 250 ml solution in distilled water was prepared using volumetric flask,), from which 10 ppm Cr(VI) solution was prepare by dilution. It is used as working standard, from working standard solutions for calibration curve were prepared as per following table. Table 3.1.1: Amount of different solution for analysis of Cr(VI) Sr. No. ml of working standard Ml of 2N H 2 SO 4 Quantity of DPC reagent (Blank) From sample appropriate quantity was used (0.1 to 3ml) so that, absorbance of resulted solution remains below 0.8. Sample solution for spectrophotometric analysis was prepared same as that of standard solution. Absorbance of standard and sample was determined at 540nm against blank. Each sample was prepared in triplicate. The result represented is mean of triplicate analysis. From concentration and absorbance of standard calibration curve was prepared. Calculation: Amount of Cr(VI) in sample = analysis. absorbance of sample dilution factor slope of calibreation curve Dilution factor depends upon total volume of sample, and volume of sample used for Analysis of Cr(III): To the definite quantity of solution containing Cr(III) 1ml 2N H 2 SO 4, 1 drop of 0.1 N AgNO 3 and 100 mg potassium persulphate was added. The resulted solution was heated on boiling water bath for 20 minutes and allows cooling up to the room temperature. In the process

3 Cr(III) get oxidized to Cr(VI). Then spectrophotometric method described above was used for analysis. Alternatively Cr(III) from solution was analyzed by spectrophotometric method using oxidation method. To measured quantity of analyte solution NaOH was added till ph become alkaline (about 9 to 10) and then 0.1 ml 6% H 2 O 2 was added and placed on boiling water bath. Cooled under running water and diluted to definite volume. Then absorbance of resulted solution was determined at 370 nm. Similar way standard solution was treated absorbance was determined at 370 nm. Either comparative or calibration curve method was used for calculation of Cr(VI) in analyte solution Analysis of Cu(II): Analysis of Cu(II) was performed by solvent extraction followed by spectrophotometric method as described by Jahagirdar (Jahagirdar, 1992). Reagent used for solvent extraction was 8-hydroxyquinoline. 0.1 M 8-hydroxyquinoline was prepared in 2M acetic acid. Standard solution of Cu(II) for analysis was prepared from A. R. grade copper sulphate. 25 ppm working standard solution of Cu(II) was prepared in distilled water g CuSO 4.5H 2 O (molecular weight g) was weight accurately and 1000 ml solution was prepared in distilled water. Standard solutions of for calibration curve were prepared as per following table. ph of each solution should be around 3 at which nearly 100% extraction of Cu(II)- 8- hydroxy quinoline complex take place into chloroform. If not ph is adjusted 3 by addition of 0.1N H 2 SO 4 or NaOH. Sr. No. Table 3.1.2: Amount of different solution taken from analysis of Cu(II) ml of 25ppm standard solution ml of water ml of 0.1M 8-hydroxidyquinoline ml (Blank) By similar way sample solution were prepared. For preparation of solution appropriate quantity of sample was used (0.2 to 5 ml). Quantity of sample used was selected by trial and

4 error so that, absorbance of sample always lies below 0.5. Then each standard and sample was carefully extracted with 5 ml chloroform. Chloroform layer was separated from aqueous layer by separating funnel and withdrawn into dry test tube containing 200 mg oven dried sodium sulphate. Absorbance of standard and sample was determined at 420 nm against blank. Each sample was prepared in triplicate. The result represented is mean of triplicate analysis. From concentration and absorbance of standard calibration curve was prepared. Calculation was done using following formula. Calculation: Amount of Cu(II) in sample = Spectrophotometric Analysis of Ni(II): absorbance of sample dilution factor slope of calibreation curve Analysis of Ni(II) was performed by solvent extraction followed by spectrophotometric method as described by Vogel (1992). Complexing agent used for solvent extraction was dimethyl glyoxime (DMG). 1% DMG was prepared in 50% ethanol. Standard solution of Ni(II) for reference was prepared from A. R. grade Nickel sulphate. 25 ppm working standard solution of Ni(II) was prepared in distilled water g NiSO 4.7H 2 O (molecular weight g) was weight accurately and 1000 ml solution was prepared in distilled water. Standard solutions of for calibration curve were prepared as per following table. ph of each solution should be around 8 at which nearly 100% extraction of Ni(II)-DMG complex take place into chloroform. If not ph is adjusted 8 by addition of 0.1 N H 2 SO 4 or NH 4 OH. Table 3.1.3: Amount of different solution for analysis of Ni(II): Sr. ml of 25 ppm ml of water ml of 1% DMG No. standard solution ml (Blank) 2 2 By similar way sample solution were prepared. For preparation of solution appropriate quantity of sample was used (0.2 to 5 ml). Quantity of sample used was selected by trial and error so that, absorbance of sample always lies below 0.5. Then each standard and sample was carefully extracted with 5 ml chloroform (two times- 3+2 ml). Chloroform layer was separated

5 from aqueous layer by separating funnel and withdrawn into dry test tube containing 200 mg oven dried sodium sulphate. Absorbance of standard and sample was determined at 366 nm against blank. Each sample was prepared in triplicate. The result represented is mean of triplicate analysis. From concentration and absorbance of standard calibration curve was prepared. Calculation was done using following formula. Calculation: Amount of Ni(II) in sample = absorbance of sample total valume of solution slope of calibreation curve ml used for analysis 3.2 Source of Electroplating Effluent Untreated chrome-electroplating effluent and original electroplating effluent was procured from small scale electroplating unit located in Chaken industrial area, Pune, India. The sample is provided on the basis of agreement that, we will use sample only for our research purpose and we will not disclose the results and name of the industry. 3.3 Analysis of Electroplating Effluent Analysis of electroplating effluent was carried out by volumetric method for Cr(VI). Likely, original electroplating effluent was also analyzed by volumetric method. Acid contained of electroplating effluent and electroplating solution was determined by titration with standardized NaOH solution. ph of electroplating solution was determined by using ph meter (Elico (India) LI 120, Hyderabad, India). Before use of ph meter, it was standardized with buffer of ph 4 (Potassium hydrogen phthalate 0.05 M) (Vogel, 1964). After appropriate dilution of electroplating effluent, UV-Visible spectra was recorded using the double beam UV-Visible spectrophotometer (Systronic, 2202 model, Ahmadabad, India). Sulphate content of electroplating effluent was analyzed by gravimetric method. To 250 ml effluent 50 ml 1% Ba(NO 3 ). 2 2H 2 O was added and stirred for 5 minutes. Then solution was digested for 30 minutes at 70 C. Then solution was filter through previously weighted Gooch

6 crucible under vacuum. Precipitate was wash with 5 ml methanol. The precipitate of BaSO 4 obtained was dried in an oven at 120 C for 3 hours. Crucible was allowed to cool to room temperature in desiccators and weighted. From difference in weight of crucible weight of BaSO 4 was obtained. 2- Calculation: g BaSO 4 = g SO Removal of Cr(VI) From Electroplating Effluent Different method were adapted for removal of Cr(VI) from electroplating effluent. In first type Cr(VI) was converted to Cr(III) by variety of reducing agents and then Cr(III) was removed from the solution. In second type of methods directly Cr(VI) was removed by precipitation Reduction of Cr(VI) to Cr(III) by different reducing agents: We have used various methods for reduction of Cr(VI) to Cr(III) from untreated electroplating effluent. Various reducing agents which are previously reported as well as some of the unreported reducing agents were used in our study. 1. Reduction of Cr(VI) to Cr(III) by elemental iron: Commercially available iron metal powder was used for this experiment. To remove any oxide present on surface of iron particles (metal powder) was treated with 3% HCl at agitation rate was at 150 rpm for 30 minutes. Afterword washed with distilled water to remove the residual acid and rinsed with acetone. Resulted iron metal powder was dried under flow of nitrogen gas and finally stored in an amber glass bottle. By using standard sieves then elemental iron particles of below 40, 40 to 60 and micron size were separated and used for experiments. Most of the experiments were carried out on 100 ml effluent. Various reaction parameter affecting rate of reaction of Cr(VI) were studied these are effect of ph, effect of particle size, effect of time, effect of stirring rate and effect of temperature. a) Effect of ph: Effect of ph on rate of reduction of Cr(VI) was studied by variation of ph from original ph to 9. To 100 ml effluent 100 mg 40 micron size elemental iron was added. ph was adjusted by addition of NaOH to requisite ph and stirred for 30 minutes at 200 rpm. Experiment was

7 performed at original ph, and at 2, 3, 4, 5, 6, 7, 8, and 9 ph independently. After 30 minutes Cr(VI) content was analyzed by spectrophotometry. b) Effect of particle size: Effect of particle size was study at original ph using particles of less than 40, 40 to 60 and 60 to 100 mesh size were used. To 100ml effluent 100 mg elemental iron of appropriate mesh size was added and stirred for 30 minutes at 200 rpm. After 30 minutes Cr(VI) content was analyzed by spectrophotometry. c) Effect of Time: Kinetics of reduction of Cr(VI) was studied by using 40 mesh size elemental iron at original ph of electroplating effluent. To 200 ml effluent 200 mg elemental iron of 40 mesh size was added and stirred for 30 minutes at 200rpm. After 30 minutes Cr(VI) content was analyzed by spectrophotometry. d) Effect of temperature: Effect of temperature on reduction of Cr(VI) was studied using 40 mesh size elemental iron at original ph of electroplating effluent. To 100 ml effluent 100 mg elemental iron of 40 mesh sizes was added and stirred for 30 minutes at 200 rpm at room temperature ( ~ 26 C). After 30 minutes Cr(VI) content was analyzed by spectrophotometry. Similar experiment was repeated at 35 and 50 C. e) Effect of dose of elemental iron: Effect of dose of elemental iron on rate reduction of Cr(VI) was studied using 40 mesh size elemental iron at original ph of electroplating effluent and at room temperature. To 100 ml effluent 20 mg elemental iron was added and stirred for 30 minutes at 200 rpm. After 30 minutes Cr(VI) content was analyzed by spectrophotometry. Similar experiment was repeated using 40, 60, 80 and 100 mg elemental iron. f) Effect of stirring rate: Effect stirring rate on reduction of Cr(VI) was studied using 40 mesh size elemental iron at original ph of electroplating effluent and at room temperature. Stirring rate was changed from 200 to 400 rpm at interval of 50 units. 2. Reduction of Cr(VI) to Cr(III) by Ferrous sulphate:

8 A.R. grade FeSO 4.7H 2 O (molecular weight g) was used for this experiment. Various reaction parameter affecting rate of reaction of Cr(VI) were studied these are effect of ph, kinetics of reaction, effect of dose of FeSO 4 and effect of temperature. a) Effect of ph: Effect of ph on rate of reduction of Cr(VI) was studied by variation of ph from original ph to 7. To 100 ml effluent 110 mg solid FeSO 4.7H 2 O was added. ph was adjusted by addition of NaOH to requisite ph and stirred for 5 minutes at 200 rpm. Experiment was performed at original ph, and at 2, 3, 4, 5, 6, and 7 ph independently. After 5 minutes Cr(VI) content was analyzed by spectrophotometry. b) Effect of Time: Kinetics of reduction of Cr(VI) was not studied since reaction between Cr(VI) and FeSO 4.7H 2 O is very fast and get completed less than 5 minutes times. c) Effect of temperature: Effect of temperature on reduction of Cr(VI) was studied using 110 mg FeSO 4.7H 2 O at original ph of electroplating effluent. To 100 ml effluent 110 mg FeSO 4.7H 2 O was added and stirred at room temperature ( ~ 26 C). Within 1 minutes reduction of Cr(VI) takes place. At 35 and 50 C reduction of Cr(VI) occur instantly. d) Effect of dose of FeSO. 4 7H 2 O: Effect of dose of FeSO 4.7H 2 O on rate reduction of Cr(VI) was studied using 70 mg to 210 mg solid FeSO 4.7H 2 O at original ph of electroplating effluent and at room temperature. To 100 ml effluent 70 mg FeSO 4.7H 2 O was added and stirred. After 5 minutes Cr(VI) content was analyzed by spectrophotometry. Similar experiment was repeated at 110, 140, 175 and 210 mg solid FeSO 4.7H 2 O. 3. Reduction of Cr(VI) to Cr(III) by Sodium sulphide: A.R. grade sodium sulphide (mol. Wt g) was used for this experiment. Various reaction parameter affecting rate of reaction of Cr(VI) were studied, these are effect of ph, effect of time, effect of dose of Na 2 S and effect of temperature. a) Effect of ph:

9 Effect of ph on rate of reduction of Cr(VI) was studied by variation of ph from original ph to 9. To 100 ml effluent 1ml 0.5 M Na 2 S solution was added. ph was adjusted by addition of NaOH to requisite ph and stirred for 30 minutes at 200 rpm. Experiment was performed at original ph and at 2, 3, 4, 5, 6, 7, 8 and 9 ph independently. After 30 minutes Cr(VI) content was analyzed by spectrophotometry. b) Effect of Time: Kinetics of reduction of Cr(VI) was studied using 1ml 0.5 M Na 2 S at original ph of electroplating effluent. To 200 ml effluent 2 ml 0.5 M Na 2 S was added and stirred for 30 minutes at 200 rpm. After 30 minutes Cr(VI) content was analyzed by spectrophotometry. c) Effect of temperature: Effect of temperature on reduction of Cr(VI) was studied using 1ml 0.5 M Na 2 S at original ph of electroplating effluent. To 100 ml effluent 1ml 0.5 M Na 2 S was added and stirred at room temperature ( ~ 26 C). For reduction of Cr(VI) at room temperature required 75 minutes. At 35 and 50 C reduction of Cr(VI) required 15 and 12 minutes. d) Effect of dose of Na 2 S: Effect of dose of Na 2 S on rate reduction of Cr(VI) was studied using 0.5 ml to 5 ml 0.5 M Na 2 S at original ph of electroplating effluent and at room temperature. To 100 ml effluent 0.5 ml 0.5 M Na 2 S was added and stirred. After 30 minutes Cr(VI) content was analyzed by spectrophotometry. Similar experiment was repeated using 1 ml, 1.5, 2, 2.5, and 5 ml 0.5 M Na 2 S. 4. Reduction of Cr(VI) to Cr(III) by H 2 O 2 : A.R. grade 30% H 2 O 2 was used for this experiment. Various reaction parameter affecting rate of reaction of Cr(VI) were studied these are, effect of ph, effect of time on quantity of Cr(VI) reduced, effect of dose of H 2 O 2 and effect of temperature. a) Effect of ph: Effect of ph on rate of reduction of Cr(VI) was studied by variation of ph from original ph to 9. To 100ml effluent 0.1 ml 30% H 2 O 2 was added. ph was adjusted by addition of NaOH

10 to requisite value and stirred for 30 minutes at 200 rpm. Experiment was performed at original ph and at 2, 3, 4, 5, 6, 7, 8 and 9 ph independently. After 30 minutes Cr(VI) content was analyzed by spectrophotometry. b) Effect of Time: Effect of time on quantity of Cr(VI) reduced was studied using 200 ml effluent and 0.2 ml 30% H 2 O 2 at original ph of electroplating effluent. To 200 ml effluent 0.2 ml 30% H 2 O 2 was added and stirred for 30 minutes at 200 rpm. After 30 minutes Cr(VI) content was analyzed by spectrophotometry. c) Effect of temperature: Effect of temperature on reduction of Cr(VI) was studied using 0.1 ml 30% H 2 O 2 at original ph of electroplating effluent. To 100 ml effluent 0.1 ml 30% H 2 O 2 was added and stirred at room temperature (26 C). Similarly reaction was performed at 35 and 45 C. d) Effect of dose of 30% H 2 O 2 : Effect of dose of 30% H 2 O 2 on rate reduction of Cr(VI) was studied using 0.02 to 1.2 ml 30% H 2 O 2 at original ph of electroplating effluent and at room temperature. To 100 ml effluent 0.02 ml 30% H 2 O 2 was added and stirred. After 30 minutes Cr(VI) content was analyzed by spectrophotometry. Similar experiment was repeated using 0.05 ml, 0.1, 0.15, 0.2, and 1.2 ml 30% H 2 O Reduction of Cr(VI) to Cr(III) by Sodium thiosulphate: A.R. grade sodium thiosulphate was used for this experiment. Various reaction parameter affecting rate of reaction of Cr(VI) were studied these are effect of ph, kinetics of reaction, effect of dose of sodium thiosulphate and effect of temperature. a) Effect of ph: Effect of ph on rate of reduction of Cr(VI) was studied by variation of ph from original ph to 5. To 100 ml effluent 70 mg sodium thiosulphate was added. ph was adjusted by addition of NaOH to requisite ph and stirred for 30 minutes at 200 rpm. Experiment was performed at

11 original ph, and at 2, 3, 4, and 5 ph independently. After 30 minutes Cr(VI) content was analyzed by spectrophotometry. b) Effect of dose of sodium thiosulphate: Effect of dose of sodium thiosulphate on rate reduction of Cr(VI) was studied using 50 mg to 110 mg sodium thiosuphate at original ph of electroplating effluent and at room temperature. To 100 ml effluent 50 mg sodium thiosulphate was added and stirred. After 30 minutes Cr(VI) content was analyzed by spectrophotometry. Similar experiment was repeated using 70, 90, 110 mg sodium thiosulphate. b) Effect of Time: Effect of time on quantity of Cr(VI) reduced was studied on 70 mg sodium thiosulphate at original ph of electroplating effluent. To 100 ml effluent 70 mg sodium thiosulphate was added and stirred for 30 minutes at 200 rpm. After 30 minutes Cr(VI) content was analyzed by spectrophotometry. c) Effect of temperature: Effect of temperature on reduction of Cr(VI) was studied using 70 mg sodium thiosulphate at original ph of electroplating effluent (this is the optimized quantity of sodium thiosulphate at which nearly 100% reduction of Cr(VI) to Cr(III) was observed). To 100 ml effluent 70 mg sodium thiosulphate was added and stirred at room temperature (26 C) and Cr(VI) content was analyzed by spectrophotometry. Similarly reaction was performed at 35 and at 45 C. 6. Reduction of Cr(VI) to Cr(III) by Hydrazine sulphate: A.R. hydrazine sulphate was used for different experiments for reduction of Cr(VI). Various reaction parameter affecting rate of reaction of Cr(VI) were studied these are effect of ph, effect of time on quantity of Cr(VI) reduced, effect of dose of hydrazine sulphate and effect of temperature. a) Effect of ph: Effect of ph on rate of reduction of Cr(VI) was studied by variation of ph from original ph to 6. To 100 ml effluent 0.5 ml mg/ml hydrazine sulphate was added. ph was adjusted

12 by addition of NaOH to requisite ph and stirred for 30 minutes at 200 rpm. Experiment was performed at original ph, and at 2, 3, 4, 5, and 6 ph independently. After 30 minutes Cr(VI) content was analyzed by spectrophotometry. b) Effect of dose of hydrazine sulphate: Effect of dose of hydrazine sulphate on rate reduction of Cr(VI) was studied using 0.2 to 1 ml of mg/ml hydrazine sulphate at original ph of electroplating effluent and at room temperature. To 100 ml effluent 0.2 ml of mg/ml hydrazine sulphate was added and stirred. After 30 minutes Cr(VI) content was analyzed by spectrophotometry. Similar experiment was repeated using 0.4, 0.6, 0.8, and 1 ml of mg/ml hydrazine sulphate. c) Effect of time on quantity of Cr(VI) reduced: Kinetics of reduction of Cr(VI) was studied using 0.5 ml mg/ml hydrazine sulphate at original ph of electroplating effluent. To 100 ml effluent 0.5 ml mg/ml hydrazine sulphate was added and stirred for 30 minutes at 200 rpm. After 30 minutes Cr(VI) content was analyzed by spectrophotometry. d) Effect of temperature: Effect of temperature on reduction of Cr(VI) was studied using 0.5ml mg/ml hydrazine sulphate at original ph of electroplating effluent. To 100 ml effluent 0.5 ml mg/ml hydrazine sulphate was added and stirred at room temperature ( ~ 26 C). Similarly reaction was performed at 35 and at 45 C Reduction of Cr(VI) to Cr(III) by Different Plant Biomasses: In this experiment for conversion of Cr(VI) to Cr(III) we have used costless and easily available plant biomasses in place of chemical reducing agents. Table shows the different plant and their part used for reduction of hexavalent chromium. Sr. No. Name of plant Part used 1 Eichornia Leaves 2 Cabbage leaves 3 Califlower leaves

13 1. Source of plant biomass: 4 Sesuvium Stem and leaves 5 Colocasia Arum (non- edible Varity) Leaves 6 Mixed weed biomass Stem and Leaves Fresh plant biomass of plants such as cabbage leaves, cauliflower leaves, Sesuvium, Colocasia Arum (non-edible varity) and mixed biomass of common weeds are obtained from farmland, while Eichornia bimass was collected from the basin of Indrayani or Pavna rivers. From December to June ample of Eichhornia grows in the basin of these rivers. Every time fresh biomass was used. Collected biomass was washed with tap water, then rinsed with distilled water, packed in polyethylene bags and stored in refrigerator. 2. Reduction of Cr(VI) to Cr(III) by plant biomass: a) Preliminary experiment: In this experiment we have tested ability of plant biomasses as a reducing agents towards Cr(VI). Experiment was performed on 50 ml of effluent under ambient condition of reaction. To 50 ml effluent 2 g crushed biomass of plant was added and suspension was stirred at 200 rpm for 1 hr. After 1 hour suspension was filtered and analyzed for Cr(VI) content by spectrophotometry. For each plant biomass experiment was carried out separately. b) Effect of ph on quantity of Cr(VI) reduced: ph of 100 ml effluent was adjusted to requisite value ±0.1 (1.5, 2 to 9 changed by 1 unit) by addition of 0.1 N NaOH. Appropriate quantity of crushed biomass of respective plant species was added and stirred for 45 minutes on magnetic stirrer. Resulted suspension was filtered and filtrate was analyzed for Cr(VI) content by spectrophotometric method. For each plant biomass experiment was carried out independently at mentioned ph values. c) Effect of biomass to effluent ratio on percentage of Cr(VI) reduced: This experiment was performed at original ph of electroplating effluent. Biomass to effluent ration (w/v) was varied from 2:100 to 12:100. The effluent containing biomass at particular ratio was stirred at 100 rpm for 45 minutes. Resultant suspension was filtered and filtrate was analyzed for Cr(VI) content by

14 the spectrophotometric method. For each plant biomass experiment was carried out independently. Weight 5 g fresh plant biomasses, and dry in oven at 90 0 C. d) Effect of contact time on percentage of Cr(VI) reduced: To 200 ml effluent definite quantity of crushed biomass of respective plant as shown in table was added and stirred for 90 minutes. The quantity of biomass selected is the optimized quantity for respective biomass. At definite time interval 5 ml solution was withdrawn and analyzed for Cr(VI) content by spectrophotometric method. For each plant biomass experiment was carried out independently. Name of biomass Table 3.4.3: Quantity of crushed biomass of respective plant biomass Eichhornia Sesuvium Cabbage leaves Cauliflower leaves Mixed weed biomass Colocasia Arum Amount of biomass (g) Ml of effluent e) Effect of temperature: To 100 ml effluent definite quantity of crushed biomass of respective plant as shown in table 3.3 was added and placed in water bath at definite temperature [room temperature (26 C), 35, 50, 75 and 90 C]. The quantity of biomass selected is the optimized quantity for respective biomass. Suspension was stirred till nearly 100% reduction of Cr(VI) take place from solution. Time required for 100% reduction was recorded. For each plant biomass experiment was carried out independently at selected temperatures. Table 3.4.3: Effect of temperature on reduction of Cr(VI) Biomass Eichhornia Sesuvium Amount of biomass ml of effluent Colocasia Arum Cabbage leaves Cauliflower leaves Mixed grass 5 g 12 g 6 g 12 g 12 g 10 g 100 ml 100 ml 100 ml 100 ml 100 ml 100 ml

15 f) Effect of stirring rate: Effect of stirring rate was studied at 250, 350 and 450 rpm. To 100 ml effluent optimized quantity of biomass was added and stirred at definite rpm for 60 minutes. After 60 minutes suspension was filter and analyzed for Cr(VI) content. For each plant biomass separate experiment is carried out at selected values of rpm.

16 3.4.3 Reduction of Cr(VI) to Cr(III) by Activated charcoal: For reduction of Cr(VI) to Cr(III) from industrial effluent we have to used activated charcoal as adsorbent. In this experiment we studied different parameters such as effect of ph, effect of different quantity of activated charcoal, study of kinetics, effect of temperature and per gram capacity of activated charcoal. The parameters studied in this method are explained one by one as follows. a) Effect of ph for reduction on Cr(VI): In this parameter ph of 100 ml effluent was studied at ph 1.5, 2 to 7 changed by 1 by addition of 0.1 N NaOH. To each flask containing 100 ml effluent 0.1 g activated charcoal was added in and stirred for 30 minutes on magnetic stirrer. Resulted suspension was filtered and filtrate was analyzed for Cr(VI) content by spectrophotometric method. For each ph experiment was carried out independently.

17 b) Effect of different quantity of activated charcoal to effluent ratio on reduction of Cr(VI): Effect of activated charcoal to effluent ratio was carried out for varying the quantity of activated charcoal. This experiment was performed at different charcoal to effluent ratio from 0.05:100 to 0.5:100 (w/v i.e. g/ml). After 30 minutes filter the supernatant solution and resultant solution was analyzed for Cr(VI) by spectrophotometric method. c) Kinetic of Cr(VI) reduction: To 200 ml effluent 0.2 g activated charcoal was added and stirred for 60 minutes. The quantity of activated charcoal was selected is the optimized quantity. At definite time interval 5 ml solution was withdrawn and analyzed for Cr(VI) content by spectrophotometric method. d) Effect of Temperature: In this parameter we studied the reduction of Cr(VI) at different temperature. To 100 ml effluent 0.1 g activated charcoal was added and placed in water bath at definite temperature [room temperature (26 C), 35, and 50 C]. Suspension was stirred till nearly 100% reduction of Cr(VI) take place from solution. Time required for 100% reduction was recorded. e) Per gram capacity: Per gram reduction capacity of activated charcoal towards Cr(VI) was evaluated by using of same activated charcoal repeatedly in batch experiment. Experiment was performed at 1g activated charcoal and 300 ml effluent for a batch. After complete reduction of Cr(VI) from 300 ml effluent, activated charcoal was separated by centrifugation and transferred into next batch of 300 ml effluent. Same experiment was repeated till activated charcoal was not able to reduce Cr(VI) from solution. f) Effect of particle size of activated charcoal: This experiment was carried out at different size of activated charcoal. For this purpose we selected activated charcoal of three different sizes i) 0-100µ, ii) µ and iii) µ. Experiment was performed on 100 ml effluent and 100 mg activated charcoal. The resulted suspension was stirred for 60 minutes, effluent was centrifuged and analysis of Cr(VI) content by spectrophotometric method. 3.5 Removal of Cr(III) from Effluent where Cr(VI) Reduced to Cr(III):

18 3.5.1 Removal of Cr(III) after treatment with Chemical reducing agents: Cr(VI) was converted into Cr(III) by using different chemical reducing agents such as Fe metal, H 2 O 2, FeSO. 4 5H 2 O, Na 2 S, NH 2 NH 2 H 2 SO 4, and Na 2 S 2 O 3.7H 2 O. Removal of Cr(III) was done by precipitation from pretreated effluent i.e. after reduction of Cr(VI) to Cr(III). For every reducing agent used for reduction of Cr(VI) different strategy is needed for removal of Cr(III) Removal of Cr(III) after reduction of Cr(VI) by Fe metal: Effluent treated with Fe metal was used for removal of Cr(III). Fe treated effluent consist of Cr(III) and Fe(III). ph of solution was adjusted by drop wised addition of 0.1 N NaOH. ph was varied from 3 to 7 by one unit. Solution was stirred for half hr and filtered through Whatman filter 41. From filtrate chromium and iron content was determined by spectrophometric method. At each ph experiment was carried out independently Removal of Cr(III) after reduction of Cr(VI) by FeSO 4 : The effluent treated with FeSO 4 consist of Fe(III) and Cr(III). Thus it is necessary to removed Cr(III) as well as Fe(III) from FeSO 4 treated effluent. In first step we have studied effect of ph on removal of Cr(III) and Fe (III). ph of solution was adjusted by drop wised addition of 0.1 N NaOH. ph was varied from 3 to 7 by one unit. Solution was stirred for half hours and filter through what man 41. From filtrate chromium and iron content was determined by spectrophometric method Removal of Cr(III) after reduction of Cr(VI) by H 2 O 2 : The effluent treated with 30% H 2 O 2 consist of Cr(III) only. In first two reducing agent Fe(III) is present in solution which act as coagulant for Cr(III). In this method we are using activated charcoal as adsorbent / coagulant for Cr(III). Removal of Cr(III) from 30% H 2 O 2 treated effluent was done in presence of activated charcoal as an adsorbent to Cr(OH) 3. In first step we have studied effect of ph on removal of Cr(III). To 100 ml H 2 O 2 treated effluent 100 mg activated charcoal was added and ph was adjusted to appropriate value by drop wised addition of 0.1 N NaOH. ph was varied from 3 to 7 by one unit. Solution was stirred for one hours and charcoal was allowed to settle. Supernatant was withdrawn and analyzed for chromium content by spectrophometric method.

19 Kinetics of removal of Cr(III) was studied at best ph. To 200 ml effluent 200 mg activated charcoal was added and ph was adjusted to 6.5 (ph at which nearly complete removal of Cr(III) takes place). Resulted suspension was stirred for 30 minutes. At definite time interval 5 ml suspension was withdrawn, centrifuged and supernatant was analyzed for chromium content Removal of Cr(III) after reduction of Cr(VI) by sodium thiosulphate: The effluent treated with sodium thiosulphate consist of Cr(III) only. Removal of Cr(III) from sodium thiosulphate treated effluent was done in presence of activated charcoal. In presence of activated charcoal and at ph 6.5 Cr(III) converted to Cr(OH) 3. In first step we have studied effect of ph on removal of Cr(III). To 100 ml sodium thiosulphate treated effluent 100 mg activated charcoal was added and ph was adjusted to appropriate value by drop wised addition of 0.1 N NaOH. ph was varied from 3 to 7 by one unit. Solution was stirred for one hours and charcoal was allowed to settle. Supernatant was withdrawn and analyzed for chromium content by spectrophometric method. Kinetics of removal of Cr(III) was studied at best ph. To 200 ml effluent 200 mg activated charcoal was added and ph was adjusted to 6.5 (ph at which nearly complete removal of Cr(III) takes place). Resulted suspension was stirred for 45 minutes. At definite time interval 5 ml suspension was withdrawn, centrifuged and supernatant was analyzed for chromium content Removal of Cr(III) after reduction of Cr(VI) by hydrazine sulphate: After reduction of Cr(VI) to Cr(III) by hydrazine sulphate next part is complete removal of Cr(III) from effluent. Cr(III) from treated effluent was removed adsorbed on activated charcoal and Cr(III) converted into Cr(OH) 3. For complete removal of Cr(III) from effluent first part is to selected appropriate ph. To 100 ml hydrazine sulphate treated effluent 100mg activated charcoal was added and ph was adjusted to appropriate value by drop wised addition of 0.1 N NaOH. ph was varied from 3 to 7 by one unit. Solution was stirred for one hours and charcoal was allowed to settle. Supernatant was withdrawn and analyzed for chromium content by spectrophometric method. For kinetic studied 200 ml effluent add 200 mg activated charcoal and ph was adjusted to 6.5, which is best ph for removal of Cr(III). Resulted suspension was stirred for 90 minutes. At definite time interval 5 ml suspension was withdrawn, centrifuged and supernatant was analyzed for chromium content Removal of Cr(III) from plant biomasses treated effluent:

20 The effluent treated with plant biomass consists of dissolved bio-molecules. For removal of Cr(III) from effluent we have tried different adsorbent to remove dissolved bio-molecules and Cr(III) simultaneously. The adsorbent used includes kaolin, SiO 2 ZnO, and activated charcoal. Among these adsorbent best results ate obtained with activated charcoal and alum. The effluent (500ml) which was previously treated with plant material was taken into beaker and to it 5 ml 5% alum solution was added (this is the optimized quantity of which result was not represented). The resulted solution was stirred for 10 minutes and then treated with different adsorbent. Weight quantity of adsorbent was added to the solution and stirred for 60 minutes. Adsorbent was allowed to settle and supernatant was used for determination of turbidance. In the experiment activated charcoal treated filtered showed lowest turbidance. Thus for clarification of plant biomass treated effluent alum and activated charcoal system was used. Thus, to plant biomass treated effluent requisite quantity of alum solution was added, stirred for 10 minutes and filtered through bed of activated charcoal. Resulted filtered was used for removal of Cr(III). For removal of Cr(III) we have selected the appropriate ph. To 100 ml effluent 100 mg powdered activated charcoal was added and ph of solution was adjusted to requisite value. ph was changed from 3 to 7 by one unit. Solution was stirred for 1 hr and charcoal was allowed to settle. Requisite quantity of supernatant was withdrawn and analyzed for Cr(III) content. Kinetics of removal of Cr(III) was studied at best ph. To 200 ml effluent 200 mg activated charcoal was added and ph was adjusted to 6.5 (ph at which nearly complete removal of Cr(III) takes place). Resulted suspension was stirred for 45 minutes. At definite time interval 5 ml suspension was withdrawn, centrifuged and supernatant was analyzed for chromium content Removal of Cr(III) after reduction of Cr(VI) with activated charcoal: The effluent treated with activated charcoal consist of Cr(III) only. The Cr(III) from effluent was completely removal in presence of activated charcoal. In this method Cr(III) was converted to Cr(OH) 3 and then removed by adsorption on activated charcoal. In first step we have studied effect of ph on removal of Cr(III). To 100 ml effluent containing Cr(III) 100 mg activated charcoal was added and ph was adjusted to appropriate value by drop wised addition of 0.1 N NaOH. ph was varied from 3 to 7 by one unit. Solution was stirred for 30 minutes and

21 charcoal was allowed to settle. Supernatant was withdrawn and analyzed for chromium content by spectrophometric method. At each ph experiment was carried out independently. In kinetics study removal of Cr(III) was done at best ph. To 200 ml effluent 200 mg activated charcoal was added and ph was adjusted to 6.5 (ph at which nearly complete removal of Cr(III) takes place). Resulted suspension was stirred for 45 minutes. At definite time interval 5 ml suspension was withdrawn, centrifuged and supernatant was analyzed for chromium content. Similarly experiment were Carried out using hematite ore as an adsorbent in place of activated charcoal. However, Cr(III) was removed where hydrazine sulphate is used as reducing agent Removal of Cr(III) by using cation exchange resin (Amerlite IR- 120) : a. Effect of ph on removal of Cr(III): Glass column with Teflon coke of internal diameter 18 mm and height 45 cm was used in the experiment. Cation exchange resin (Amerlite IR -120) of Loba Chemical Company was used. Before used resin it was soaked in distilled water for 24 hours. Column was packed with this resin up to 10 cm height (~ 4 g). Then resin in column was washed with 100ml distilled water. Above the column separating funnel of 250 ml capacity was attached. Into funnel 100 ml effluent containing Cr(III) was filled. Then from funnel Cr(III) solution was allowed to passed into column and simultaneously column was eluted at the rate of 1 ml/min. 100 ml elute was collected from column and analyzed for Cr(III) content. Same experiment was performed at 2, 3, 4, and 5 (above ph 5 Cr(III) start precipitating as Ca(OH) 3 hence, greater ph than 5 are not used in the experiment). From this experiment best ph for removal of Cr(III) on ion exchange resin was selected. b. Per gram Cr(III) exchange capacity of cation exchange resin: For this experiment column was packed with 2 g resin (resin was prepared as explain above). Then resin in column was washed with 100 ml distilled water. Above the column separating funnel of 250 ml capacity was attached. Into funnel effluent containing Cr(III) was filled. The ph of effluent filled into funnel was previously adjusted to 3 (optimum ph for removal of Cr(III) on Amberlite IR-120 cation exchange resin). Then from funnel Cr(III) solution was allowed to passed into column and simultaneously column was eluted at the rate of

22 1ml/min. fraction of 50 ml were collected and analyzed for chromium content. 50 ml fractions were collected till elute shows appreciable higher quantities of Cr(III). From this data graph was prepared (ml of effluent vs quantity of chromium was plotted). From this graph per gm chromium (III) exchange capacity of resin was estimated. c. Regeneration of ion exchange resin: The column used for removal of Cr(III) was washed with 50 ml 2 N H 2 SO 4. During washing column was eluted at very slow rate (0.4 ml/min) followed by washing with distilled. The regenerated resin was used again for removal of Cr(III). 3.6 Removal of Cu(II), and Ni(II) in Presence of Cr(III) from Effluent: Copper and Nickel electroplating is also one of the common industries like chrome electroplating industries. So, in present investigation along with chromium we also removed copper and nickel. Removal of copper, nickel and chromium from effluent can be done by using various methods. In our work these metal can be adsorbed by using activated charcoal and hematite Removal of Cu(II): Cu(II) solution of 25 ppm was prepared in water and used in present study. As we obtained best results for removal of Cr(III) on activated charcoal and hematite ore we have used both of these adsorbent for removal of Cu(II) and Ni(II) in presence of activated charcoal and hematite ore. Before using mixture of Cu(II) and Ni(II) with Cr(III), experimental parameters for individual ions for Cu(II) and Ni(II) were optimized. 1) Removal of Cu(II) in presence of activated charcoal: a) Effect of ph: Removal of Cu(II) as hydroxide is governed by ph of solution. Thus, to obtain best ph for removal of Cu(II) as hydroxide ph of solution was varied from 3 to 7. Into 100 ml Cu(II) ion solution add 100 mg charcoal and adjust ph of solution to requisite value. Stir the solution for 1 hr. and then Cu(II) was analyzed from solution by spectrophotometric method. b) Effect of different amount of activated charcoal:

23 In this parameter quantity of activated charcoal was varied from 25 mg to 150 mg at interval of 25 mg. In experimental part into 100 ml of effluent add requisite quantity of activated charcoal and stirred for 1 hr., followed by filtration and filtrate was analyzed for Cu(II) content by spectrophotometric method. c) Effect of time on quantity of Cu(II) removed: This experiment was carried out on 200 ml effluent with addition of 200 mg activated charcoal. Adjust ph of resultant solution to best ph of removal of Cu(II). At different time interval 5 ml suspension was withdrawn and analyzed for Cu(II) content by spectrophotometry. d) Turbidimetric Experiment: Turbidance of Cu(II) solution was determined at different ph from 4 to 9. ph was Cu(II) solution was adjusted to definite value at regular interval and at each ph turbidance of solution was determined. 2) In presence of Hematite: Similar to activated charcoal, removal of Cu(II) was performed in presence of hematite ore. All parameters are studied are same as that of activated charcoal Removal of Nickel: In this experiment we used standard nickel solution (25 ppm). Removal of Ni(II) was studied as that Cu(II). All experimental parameters affecting removal of Ni(II) were optimized and then removal of Ni(II) was done in presence of Cu(II) and Cr(III). 1) Removal of Ni(II) in presence of activated charcoal: a) Effect of ph: Removal of Ni(II) as hydroxide is governed by ph of solution. Thus, to obtain best ph for removal of Ni(II) as Ni(OH) 2, ph of solution was varied from 3 to 9. Into 100 ml Ni(II) ion solution add 100 mg charcoal and adjust ph of solution to requisite value. Stir the solution for 1 hr. and then analyzed it for Ni(II) content by spectrophotometric method. b) Effect of different amount of activated charcoal:

24 In this parameter quantity of activated charcoal was varied from 25 mg to 150 mg at interval of 25 mg. Into 100 ml of effluent add requisite quantity of activated charcoal and stirred for 1 hr. It was followed by filtration and filtrate was analyzed for Ni(II) content by spectrophotometric method. c) Effect of time on quantity of Ni(II) removed: This experiment was performed on 200 ml effluent with addition of 200 mg activated charcoal. Adjust ph of resultant solution to best ph of removal of Ni(II). At different time interval 5 ml suspension was withdrawn and analyzed for Ni(II) content by spectrophotometric method. d) Turbidimetric Experiment: Turbidance of Ni(II) solution was determined at different ph from 4 to 9. ph of Ni(II) solution was adjusted to definite value at regular interval and at each ph turbidance of solution was determined. This experiment was performed to know the exact form of Ni(II) in aqueous solution at which maximum quantity of Ni(II) get removed from solution on activated charcoal. 2) In presence of hematite ore as an adsorbent: Similar to activated charcoal Ni(II) from solution was removed in presence of hematite ore as an adsorbent Combine removal of Cu(II), Ni(II) and Cr(III): Cr(VI) from effluent was converted to Cr(III) by using activated charcoal. To it Cu(II) and Ni(II) was added at the concentration of 25 ppm. ph of this solution was adjusted to optimum ph of removal of metals i.e. to 7 and to it activated charcoal was added at concentration 1 mg per ml. resultant suspension was stirred for 1 hr. and analyzed for Cu(II), Ni(II) and Cr(III) content by spectrophotometry. Similar method was followed for removal of Cu(II), Ni(II) and Cr(III) by using hematite ore as an adsorbent. 3.7 Removal of Cr(VI) by Precipitation: Cr(VI) in dichromate or in chromate form can be precipitated with various precipitating reagents. This include Pb(II), Ba(II), and Fe(OH) 3. Thus in our study we have used these three precipitating agents for removal of Cr(VI) from effluent.

25 3.7.1 Precipitation of Cr(VI) by Pb(II): Lead react with chromate or dichromate ions to give rise formation of yellow coloured insoluble precipitated i.e. lead chromate. For removal of Cr(VI) we have used lead nitrate as a source of Pb(II) ion. Various reaction conditions were optimized. a) Effect of lead nitrate dose: Effluent consist of Cr(VI) and SO Pb(II) react with both of these ions giving rise to formation of precipitate of lead chromate and lead sulfate. In acidic ph chromate and sulphate get precipitated respectively as lead sulfate and lead chromate. The ph 4 is the preferred ph for precipitation of lead as lead chromate (Vogel, 1964). Thus to study effect of lead nitrate dose experiment was performed at ph 4. To 100 ml effluent where quantity of lead nitrates was added and stirred for 30 minutes. After 30 minutes Cr(VI) contain in the supernatant solution was determined by spectrophotometric method. The quantity of lead nitrate was varied as 0.6, 0.65, 0.7, 0.75 and 8 g. For each quantity experiment was carried out independently. b) Effect of ph: Electroplating effluent is highly acidic hence, for complete removal of Cr(VI) ph was optimized. ph was varied by adding of 0.1 N NaOH from 1.5, and 2 to 7 varied by one unit. Experiment was performed on 100 ml effluent. To 100 ml effluent optimized quantity (0.65 g) lead nitrate was added and stirred for 30 minutes. Then supernatant was analyzed by spectrophotometric method for the quantity of Cr(VI) in the supernatant solution. c) Kinetics of removal of Cr(VI) : To 100 ml effluent 0.65 g Lead nitrate was added and solution was stirred for 30 minutes. At the interval of 5 min 5 ml solution was centrifuge and analyst for Cr(VI) content Removal of Cr(VI) by Ba((NO 3 ) 2 : a) Effect of barium nitrate dose: Effluent consist of Cr(VI) and SO Ba(II) react with both of these ions giving rise to formation of precipitate of barium chromate and barium sulfate. In acidic ph chromate and sulfate get precipitated respectively as barium sulfate and barium chromate. The ph 4 is the preferred ph for precipitation of Cr(VI) as barium chromate. Thus to study effect of barium nitrate dose experiment was performed at ph 4. To 100 ml effluent where quantity of barium nitrates was added and stirred for 30 minutes. After 30 minutes Cr(VI) contain in the supernatant

26 solution was determined by spectrophotometric method. The quantity of barium nitrate was varied as 0.4, 0.6, 0.8, and 1 g. For each quantity experiment was carried out independently. b) Effect of ph: Electroplating effluent is highly acidic hence, for complete removal of Cr(VI) ph was optimized. ph was varied by adding of 0.1 N NaOH. From 1.5, and 2 to 7 varied by one unit. Experiment was performed on 100 ml effluent. To 100 ml effluent optimized quantity (0.8 g) barium nitrate was added and stirred for 30 minutes. Then supernatant was analyzed by spectrophotometric for the quantity of Cr(VI) in the supernatant. c) Kinetics of removal of Cr(VI): To 100 ml effluent 0.8 g barium nitrate was added and solution was stirred for 30 minutes. At the interval of 5 min 2 ml solution was centrifuge and analyst for Cr(VI) content Removal of Cr(VI) by Fe 2 (SO 4 ) 3 by co-precipitation: a) Effect of dose of Fe 2 (SO 4 ) 3 : For removal of Cr(VI) different quantities of ferric sulphate was used. The quantities are varied from 0.5 to 2.5 g at the interval of 0.5 units. ph of 100 ml effluent was adjusted to 5 (previously reported ph) by suspension of 10% Ca(OH) 2. To it weight quantity of ferric sulfate was added and stirred for 60 minutes. After 60 minutes resulted suspension was filtered and analyzed for Cr(VI) content. b) Effect of ph on removal of Cr(VI): ph of 100 ml effluent was varied from original ph to 7 by addition of 10% Ca(OH) 2 suspension. Different solutions of ph 2, 3, 4, 5, 6, and 7 were prepared. To each of these solutions 1.5 g ferric sulphate (optimized quantity) was added and stirred for 60 minutes. After 60 minutes resulted supernatant was analyzed for Cr(VI) content by spectrophotometric method. c) Effect of time on removal of Cr(VI): To 100 ml effluent 1.5 g ferric sulphate was added and ph was adjusted to 10 (optimized ph). The solution was stirred at 200 rpm on magnetic stirrer for 3 hours. At the interval of 30 minutes 5 ml solution was removed, centrifuged and analyzed for Cr(VI) contained. d) Effect of temperature: To 100 ml effluent 1.5 g ferric sulphate was added and ph was adjusted to 10 (optimized ph). The solution was stirred at 200 rpm on magnetic stirrer for 60 minutes at room temperature.