TREATMENT OF AGRO-INDUSTRIAL AND TEXTILE WASTEWATERS BY FENTON BASED PROCESSES

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1 TREATMENT OF AGRO-INDUSTRIAL AND TEXTILE WASTEWATERS BY FENTON BASED PROCESSES José Alcides Peres Universidade de Trás-os-Montes e Alto Douro (UTAD) Vila Real, Portugal nd Summer School on Environmental Applications of Advanced Oxidation Processes Porto, Portugal, July 1-14, INTRODUCTION Agro-industries are one of the main sources of water pollution in the industrial sector. Some agro-industrial wastewaters cannot be effectively treated by conventional biological processes due to their high toxicity, low biodegradability and seasonal production. 1

2 1. Introduction Advanced oxidation processes (AOPs), a chemical approach, can be used to oxidize organic compounds found in wastewaters which are difficult to handle biologically into simpler end products. AOPs involve the generation of free hydroxyl radical (HO ), a powerful, non-selective chemical oxidant. Hydroxyl radical is one of the most active oxidizing agents known. It acts very rapidly with most organic molecules with rate constants in the order of M -1 s Introduction Standard reduction potential of some oxidizing agents Oxidising agent Eº (V, 5ºC) Fluor 3.3 Hydroxyl radical.8 Atomic oxygen.4 Ozone.7 Hydrogen peroxide 1.78 Hydroperoxil radical 1.7 Permanganate 1.68 Hipobromure acid 1.59 Chlorine dioxide 1.57 Hypochlorous acid 1.49 Hypoiodide acid 1.45 Chlorine 1.36 Bromide 1.9 Iode.54 4

3 1. Introduction Depending upon the nature of the organic species, generated hydroxyl radicals can attack organic structures by four main mechanisms : (a) hydrogen abstraction RH + HO R + H O (b) radical addition HO + X C=CX X C()-C X (c) electron transfer RX + HO RX + + HO - (d) radical combination HO + HO H O H O + HO HO + H O 5. FENTON PROCESSES.1. Fenton reagent For over a century (1894) it was first described by Henry Fenton (England) the catalytic oxidation of tartaric acid in the presence of Fe + and hydrogen peroxide. The oxidation mechanism of this system is due to the reactivity of hydroxyl radicals generated in acid medium, by the catalytic decomposition of hydrogen peroxide in the presence of Fe + : Fe + + H O Fe 3+ + HO - + HO. k = 76 M -1 s

4 .1. Fenton reagent In Fenton's reagent, in addition to the basic reaction (initiation step), it is possible to provide various competitive reactions involving Fe +, Fe 3+, H O and HO radicals: Fe HO Fe 3 HO H O H O HO 3 Fe HO Fe HO 3 Fe HO Fe O Fe 3. HO Fe H HO The catalytic action is enhanced by the reduction of Fe 3+ to Fe +. H 7 1. Introduction Agro-industrial wastewater treatment North of Portugal Olive mill wastewater (OMW) Winery wastewater (WW) Candied fruit wastewater and also: Textile industry wastewater 8 4

5 Douro Valley 9 Douro Valley 1 5

6 1. Introduction Characteristics of olive mill wastewater (OMW) Parameter Olive mill wastewater (batch process) Limit value (DL 36/98) Units ph BOD 5 COD TSS VSS Oil and fats Total polyphenols N Kjeldahl BOD 5 /COD mg O /L mg O /L mg/l mg/l mg/l mg/l mg/l - 11 CO Phenolic acids - Present in OMW ácido p-hidroxibenzóico CH=CHCO CH=CHCO CH=CHCO ácido p-cumárico ácido cafeico ácido ferúlico CO CO CO In our study of OMW treatment we thought it would be important to begin by understanding the effect of the FR on phenolic acids. ácido -resorcílico ácido protocatéquico ácido vanílico CO CO CO H3CO H 3CO ácido verátrico ácido 3,4,5-trimetoxibenzóico ácido siríngico 1 6

7 .1. Fenton reagent Fenton reagent (1) p-hydroxybenzoic acid 1 p-hydroxybenzoic acid (mg/l) Molar ratio H O :ác.phb 8:1 without Fe + 1:1 :1 3:1 4:1 5:1 8:1 1:1 :1 p-hydroxybenzoic acid We began by studying the phb acid: taken as compound model Reaction time (min) a) Effect of molar ratio H O /phb acid (4:1) Fenton reagent Fenton reagent (1) p-hydroxybenzoic acid INFLUENCE OF OPERATING VARIABLE 1 1 phb acid degradation (%) p-hydroxybenzoic acid (mg/l) Temperature 1º C º C 3º C 4º C 5º C ph Time (min) b) Effect of ph (ph=3.-3.5) c) Effect of temperature (T=3 o C) 14 7

8 .1. Fenton reagent Fenton reagent (1) p-hydroxybenzoic acid INFLUENCE OF OPERATING VARIABLE Ácido p-hidroxibenzóico (mg/l) Razão molar H O :Fe + 3:1 - (,1 mg Fe + /L) 15:1 - (4, mg Fe + /L) 3:1 - (1, mg Fe + /L) ORP (mv) Razão molar H O :ác.phb R=1 R= R=3 R=4 R= Tempo de reacção (min) Tempo de reacção (min) d) Effect of Fe + concentration ([H O ]/[Fe + ] = 15) e) ORP variation - It is observed a large increase in ORP value immediately after the addition of H O Fenton reagent Fenton reagent () Phenolic acids Oxidation experiments were performed with the Fenton reagent using the competitive kinetic method (Haag and Yao, 199). We used mixtures of these phenolic acids, with p-hb acid always being present as reference compound. ln B B k k B R ln R R - This allowed us to calculate the rate constants (3 C, ph=3.5) of the reactions between the hydroxyl radicals and the different phenolic acids. 16 8

9 .1. Fenton reagent Fenton reagent () Phenolic acids Competitive kinetic method Phenolic acid Ferulic acid p-coumaric acid Veratric acid p-hydroxybenzoic acid -Resorcilic acid Cafeic acid Siringic acid Vanillic acid 3,4,5-Trimetoxybenzoic acid Protocatechuic acid k (x 1 9 ) (L/mol.s) ,6 9,5 C H C H C O O H 9,4 C H C H C O O H CO O H CO log k HO 9,3 9, O H C O O H O H C H C H C O O H O H O H C O O H O H O H CO H 3 CO CO 9,1 CO H 3CO 9, 8,9,,,4,6,8 1, 1, 1,4 i INDUC Logarithmic representation of hydroxyl reaction constants versus Hammett constants of the substituents for the reaction of phenolic acids with HO radicals. 18 9

10 .1. Fenton reagent Fenton reagent (3) Olive mill wastewater In this case, we took as reference a global parameter: the COD value. The reduction of COD by the Fenton reagent can be summarized as follows: Stage 1: COD + H O + Fe + species partially oxidized (1) Stage : species partially oxidized + H O + Fe + CO + H O + inorganic salts () 19 Fenton reagent (3) Olive mill wastewater a) Influence of operating variables 7 Experiments with Fenton's reagent to assess the effect: concentration of H O Fe + concentration temperature initial ph COD removal (%) Reaction time (min) H O /COD=1.75 H O /COD=1.5 H O /COD=.35 b) Kinetic model (COD COD ) ln (COD COD ) Numerator and denominator are subtracted by the COD values remaining after a long time period. k D.t ln[(cod -COD inf )/(COD-COD inf )] 5,5 5, 4,5 4, 3,5 3,,5, 1,5 1,,5, Temperature 1ºC ºC 3ºC 4ºC 5ºC Time (min) 1

11 .1. Fenton reagent Fenton reagent (3) Olive mill wastewater A. Fenton reagent + B. Coagulation/Floculation/Decantation with Ca() 35 3 COD final Sludge 3 COD final (mg O /L) ,,5 1, 1,5,,5 3, R=H O /COD Sludge (% v/v) Ponderal ratio R=H O /COD effect in COD reduction of OMW and sludge percentage reduction. (Conditions: temperature=3ºc, ph initial = 3,5 e molar ratio H O /Fe + = 15:1). 1.. Photo-Fenton process.. Photo-Fenton process In aqueous solution, the ferric ion (Fe 3+ ) tends to form several complexes. Fe() + complex is the dominant for the ph range.5-5. and absorbs radiation in the UV range with larger absorption coefficient than Fe 3+ (aq). Its photolysis leads to the formation of Fe + ions and HO : Fe() + + h Fe + + HO The Fe + generated during irradiation, in the presence of H O, reacts with this giving sequence to the Fenton reaction. In this context, the reaction is catalytic and is established a cycle in which Fe + is regenerated. 11

12 .. Photo-Fenton process Photo-Fenton process The high efficiency of photo-fenton process is due to the formation of more hydroxyl radical than the Fenton reagent. UV End products CO + H O Fenton s reagent UV 3.. Photo-Fenton process Dye degradation Reactive Black 5 by photo-fenton process Reactive Black 5 (RB5) Azo dye (N=N) reactive type NaO 3 SOCH CH O S N N SO 3 Na HO H N NaO 3 SOCH CH O S N N SO 3 Na RB5 as a representative dye pollutant of textile wastewaters 4 1

13 .. Photo-Fenton process RB5 degradation - Comparison between different oxidants 1 Percentage of remaining H O UV UV and Fe H O and UV Fenton Photo-Fenton After 15 min we have 99% of RB5 degraded Time (min) C RB5 =1,x1-4 mol/l; C Fe +=1,5x1-4 mol/l; C H O = 7,3x1-4 mol/l; Temperature = o C; UV lamp = Heraeus TNN 15/3 5.. Photo-Fenton process RB5 degradation 5 NaO 3SOCH CH O S N N SO 3 Na HO 4 H N Absorbance 3 1 NaO 3 SOCH CH O S N N SO 3Na min 15 seg 3 seg min A Hora K 31 nm aromatic fraction 595 nm color Wavelength (nm) Spectrum UV/VIS: evolution over time - photo-fenton process 6 13

14 .3. Ferrioxalate.3. Iron complexes in Fenton and photo-fenton reactions The use of iron complexes in the degradation of organic contaminants in photo-fenton reaction allows the stabilization of iron in a wider range of ph values. The iron complex also contributes to increasing the light absorption efficiency by extending the range of absorption of the reaction medium for the visible region. Its photolysis is sensitive to radiation with wavelengths between and 5 nm. Potassium ferrioxalate is a Fe 3+ complex used in photochemical applications and photo-fenton processes Ferrioxalate The photolysis of Fe 3+ -oxalate (ferrioxalate) complex generates Fe + ions in acid solution, with a quantum yield () known ( = 1.-1.). Can be expressed by the following reactions: Fe(C C C 3 O 4 ) 3 hν Fe C O 4 C O 4 3 Fe(C O 4 ) 3 Fe 3C O 4 O 4 CO O 4 O O CO Adding H O photochemical reduction of Fe 3+ complex combines with the Fenton reaction generating hydroxyl radicals: Fe(CO4 ) HO hν Fe(CO4 ) HO 8 14

15 .3. Ferrioxalate Comparison between ferrioxalate process/h O /sunlight and photo-fenton 1 Reactive Black 5 (RB5) Discolouration high and very similar: Photo-Fenton = 98.7% Ferrioxalate/H O /sunlight = 96.1% RB5 Decolorization (%) Time Evolution: Ferrioxalate/H O /Solar light Fenton/UV-C Ferrioxalate [Fe(C O 4 ) 3 ] 3- + h (solar) Fe + + C O C O Time (min) C O [Fe(C O 4 ) 3 ] 3- Fe + + 3C O CO C O O O - + CO Photo-Fenton Fe + + H O Fe HO H O + h (UV) HO Fe 3+ + H O + h (UV) Fe + + H + + HO Absorvância 1 t=6 min t= min Comprimento de onda (nm) RB5 can be effectively decolorized using Fenton/UV-C and ferrioxalate/h O /solar radiation processes with a small difference between the two processes Photo-Fenton with solar radiation.4. Photo-Fenton with solar radiation The efficiency in the degradation of different classes of compounds has suggested the photo-fenton process activated by solar radiation as very attractive. Different designs of solar photocatalytic reactors: (a) no concentrating system (b) PTC - Parabolic concentrating reactor (c) CPC Compound Parabolic Collector 3 15

16 .4. Photo-Fenton with solar radiation Photochemical solar winery wastewater treatment in a CPC reactor l min -1 CPC CPCs (Vi = l) 3 x 1.3 m Tank Pump Picture and schematic representation of the CPC reactor Compound Parabolic Collector: m irradiated surface - fixed platform tilted 37º (local latitude) Normalized illumination time (t 3W ) t 3w,n = t 3w,n-1 + Δt n UV Vi, Δt n = t n - t n-1 3 V T Constant solar UV power of 3 W/m (typical solar UV power on a perfectly sunny day around noon). UV is the average solar ultraviolet radiation measured during Δt n Photo-Fenton with solar radiation Winery wastewater characteristics Simulated winery wastewater performed from: - Wine - Grape juice - Wine + grape juice - Enologic additives Effluent Synthetic sample ph Conductivity (S/cm) TOC (mg C/L) COD (mg O /L) Total polyphenols (mg Gallic acid /L) WV Wine WG Grape juice WW Wine + Grape juice (5:5)

17 .4. Photo-Fenton with solar radiation Solar photo-fenton system Photo-Fenton removes 98% of the COD load in the winery wastewater after a t 3W of 8 min. 1, TOC/TOC,8,6,4,, t 3W wine with 55 mg/l Fe + grape juice with 55 mg/l Fe + wine + grape juice with 55 mg/l Fe + wine + grape juice with mg/l Fe + For t 3W equal to 4 minutes: - wine: reduction of 54% TOC - grape juice: reduction 93% TOC Wine + grape juice (5:5): - reduction 9% TOC (55 mg/l Fe + ) - reduction 86% TOC ( mg/l Fe + ) - Toxicity decreases during the photo- Fenton reaction very significantly from 48% to 8%. At the same time, TP decrease 9%, improving wastewater biodegradability Photo-Fenton with LEDs.5. Photo-Fenton with LEDs Experimental Physicochemical characterization (candied fruit wastewater) UV-A LED photo-fenton H O (mg/l) Fe 3+ (mg/l) Reaction time (min) LED = Light Emitting Diode ph adjustment to 3; Iron addition; H O addition and simultaneously UV LED ON. Radiation source UV LED sytem I 96 InGaN Roithner RLS- UV37E LEDs (3 W/m ) 37 nm UV LED sytem II 1 InGaN Roithner APGC1-365E LEDS (7-85 W/m ) 365 nm 17

18 .5. Photo-Fenton with LEDs Candied (or crystallized) fruit wastewater Values Parameter Sample A Sample B Sample C ph (escala Sorensen) E o (mv) Conductivity (µs/cm) Turbidity (NTU) Total Suspended Solids (mg/l) Volatile Suspended Solids (mg/l) COD (mg O /L) BOD 5 (mg O /L) Toatal Polyphenols (mg galic acid/l) Biodegradability Index = BOD 5 /COD BI <.4 Non biodegradable.4 <BI<.7 Low biodegradable.7 <BI<.8 Biodegradable BI>.8 High biodegradable Sample A =.6 Sample B =.16 Sample C =.19 - Very low biodegradability (BOD 5 /COD <.19) Photo-Fenton with LEDs Optimal conditions H O (mg/l) 5459 Fe 3+ (mg/l) 86 8% 95% 99% A combination of UV-A LED photo-fenton with CFD attained a higher COD removal (8%), as well as almost total removal of turbidity (99%) and TSS (95%). COD Solids Turbidity 36 18

19 .5. Photo-Fenton with LEDs Improvement in the biodegradability index Biological treatment Subsequent biodegradability of treated effluents increased, allowing the application of a biological treatment step after the photochemical/cfd with 85 W/m CONCLUSION In this work we presented different case studies involving the Fenton process: Fenton classic p-hb acid, phenolic acids, OMW Photo-Fenton process RB5, textile wastewater Iron complexes (ferrioxalate) RB5 Photo-Fenton with solar radiation winery wastewater Photo-Fenton with LEDs candied fruit wastewater Homogeneous Fenton processes are relatively simple, environmentally friendly, versatile and economically competitive. In photo-fenton processes solar radiation and UV-A LED radiation are alternatives to conventional UV lamps in terms of ecofriendliness, operational cost and energy efficiency

20 Acknowledgements Marco Lucas (U. Loughborough) Javier Benitez (UEx) Jesus Beltrán-Heredia (UEx) Juan Garcia (UCM) Joaquín Dominguez (UEx) Sixto Malato (PSA) Manuel Maldonado (PSA) Gianluca Li Puma (U. Loughborough) Jorge Rodriguez-Chueca (U. Rey Juan Carlos) Pedro Tavares (UTAD) Rui Boaventura (FEUP) Grazie mille Merci bien Thank you very much for your attention Muchas gracias Dziękuję Muito obrigado José Alcides Peres (UTAD) Vila Real, Douro region