Photo-Fenton processes at mild conditions. Antonio Arques Campus de Alcoy, Universitat Politècnica de València

Transcription

1 Photo-Fenton processes at mild conditions Antonio Arques Campus de Alcoy, Universitat Politècnica de València

2 Photo-Fenton process The most efficient AOP that can be driven under sunlight Iron plays a photocatalytic role, but hydrogen peroxide is consumed e- - Fe 2+ + H 2 O 2 Fe 3+ + OH - + OH - hu Fe 3+ + OH - Fe 2+ + OH e-

3 Photo-Fenton process Major concerns are the amount of iron that is required and, mainly, the acidic ph that is required (optimum ph = 2.8) An alternative approach is decreasing the amount of iron and working at milder ph conditions This is interesting when dealing with effluents with low organic loading

4 Towards photo-fenton at milder conditions The ph = 2.8 required for photo-fenton is mainly due to the presence of photo-active Fe(OH) 2+ species Changes in the coordination sphere of iron results in a variation of the mechanism At higher ph values formation of photochemically non-active iron oxides or hydroxides occurs, thus decreasing the efficiency of photo- Fenton Formation of such species should be prevented

5 Approaches for photo-fenton at mild ph condition?

6 Approaches for photo-fenton at mild ph condition Low iron concentrations Use of complexing agents In situ generation of iron salts Heterogeneization Use of other metals Taking advantage of the simple matrix

7 C/C0 C/C0 Iron at low concentrations 1,00 1,00 0,75 0,75 Neutral ph 5 mg/l of EPs 0,50 0,25 0,50 0,25 0, time (min) 0, time (min) Acetaminophen Caffeine Acetaminophen Caffeine Amoxicillin Acetamiprid Amoxicillin Acetamiprid Carbamazepine Clofibric acid Carbamazepine Clofibric acid Photo-Fenton Photolysis

8 Use of other metals Some other metals can drive (photo)-fenton like processes Their behaviour might differ from that of iron (e.g. copper) Their high toxicity might be a major drawback They should only employed: Supported onto different structures When they are already present in the effluent

9 concentración (mg/l) inhibicion (%) Use of other metals t 30W (min) t 30W (min) Total CN - ( ), free CN - ( ), DOC ( ) and Cu ( ). Toxicity determined by inhibición de la luminiscencia por vibrio fischeri ( ), Inhibición de la respiración de fangos activos ( ).

10 Use of other metals t= 0; Toxicity = 75% t= 3h, Toxicity = 37% t= 6h, Toxicity = 13%

11 Heterogeneization

12 Heterogeneization Iron can be supported onto different structures: Membranes Zeolites or other clays Photochemically active inorganic iron-containig species Complexation with macromolecules ZVI The processes are generally slower because of diffusion control In most cases iron leached from the solid structures are the real key species

13 Use of complexing agents COMPLEX FORMATION Oxalate Citrate Chitosane EDTA EDDS Humic acids, Fulvic acids SBO Carboxy and phenoxy groups are prefered

14 Humic substances They are commonly found in water released from animal or vegetal debrisses They are photochemically active Humic substances constitute a major pathway for the abiotic removal of xenobiotics in the environment

15 Humic substances

16 Humic substances Removal of emerging pollutants at neutral photo-fenton in the presence of humic substances

17 Soluble bio-organic substances (SBOs) The use of SBOs might be a sustainable alternative as a waste is valorized to be employed in water detoxification Constituted by macromolecules (67 to 463 kg mol -1 ) with similar characteristics as humic substances Similar photophysical/photochemical behaviour is expectable

18 Soluble bio-organic substances (SBOs) Urban wastes Organic fraction Pre-treatments -Anaerobic digestion -Aerobic biodegradation Biomass Soluble Bio-Organics (SBO) Digestion at basic conditions Centrifugation to remove the non-soluble fraction Ultrafiltration of supernatant Drying of the retentate

19 Composition of SBOs A (FORSUD) B (CVDFT110) C (CVT230) Volatile solids (%, w/w) Carbon (%, w/w) Nitrogen (%, w/w) Si (%, w/w) Fe (%, w/w) Al (%, w/w) Mg (%, w/w) Ca (%, w/w) K (%, w/w) Na (%, w/w) Cu (mg/l) Ni (mg/l) Zn (mg/l) Cr (mg/l) Pb (mg/l) Hg (mg/l)

20 Composition of SBOs A (FORSUD) B (CVDFT110) C (CVT230) Aliphatic carbon Amine Methoxy Alkoxy Anomeric carbon Aromatic Phenolic carbon Phenoxy Carboxylic Amide Carbonilic 1-5 Lipophilic/hydrophilic ratio Aliphatic/aromatic ratio E 2 /E 3 ratio

21 What should we study?

22 What should we study? Performance of the SBO With iron Without iron Optimization of operational parameters Biocompatibility of the SBO Biodegradability Toxicity Stability and reuse Scale up and economic assessment?

23 k (min-1) Effect of SBO on photolysis Opposite effects: 0,012 0 mg/l SBO Improved generation of reactive species 0,01 0, mg/l SBO 200 mg/l SBO Pre-association pollutantcatalyst 0,006 The screen effect due to the brown color of SBOs 0,004 0,002 Competition SBO-pollutant for the reactive species 0

24 Effect of SBOs on the photolysis of 6 pollutants Conditions Rate constants with SBO were estimated if the screen effect was supressed The ratio of k with and without SBO was calculated Results k /k f 4,0 3,0 2,0 absence of H2O2 presence of H2O2 Ratios above 1 with H 2 O 2 indicate extra generation of reactive species 1,0 This was not always true for irradiation 0,0 The iron present in the SBO might drive a photo-fenton process

25 Use of SBOs in solar photo-fenton (ph = 5.2) 1,00 1,00 0,80 A 0,80 B 0,60 0,60 C/C 0 C/C 0 Without SBO 0,40 With SBO (10 mg/l) 0,40 0,20 0,20 0, t 30W (min) 0, t 30W (min)

26 ph ph Effect of the operational variables: caffeine [SBO] = 15 mg/l Contours of Estimated Response Surface BOS (mg/l)=15.0 [SBO] = 25 mg/l Contours of Estimated Response Surface BOS (mg/l)= t 50% (min) CAF 7 t 50% (min) CAF [Fe] mg/l [Fe] mg/l The photo-fenton reaction can be extended to ph values close to 5, without too remarkable loss of efficiency

27 ph ph Effect of the operational variables: amoxicillin [SBO] = 15 mg/l Contours of Estimated Response Surface BOS (mg/l)=15.0 [SBO] = 25 mg/l Contours of Estimated Response Surface BOS (mg/l)= t 50% (min) t % 90.0 (min) [Fe] mg/l [Fe] mg/l

28 [SBO] mg/l [SBO] mg/l Effect of the operational variables at ph = 5 Contours of Estimated Response Surface ph=5.0 Contours of Estimated Response Surface ph= t 50% (min) CBZ t 50% (min) AMF [Fe] mg/l [Fe] mg/l Carbamazepine Amoxicillin

29 Effect of different SBOs 1,0 A (FORSUD) 1,0 B (CVDFT 110) 1,0 C (CVT230) 0,8 0,8 0,8 C/C 0 0,6 0,4 C/C 0 0,6 0,4 C/C 0 0,6 0,4 0,2 0,2 0,2 0, time (min) 0, time (min) 0, time (min)

30 toxicity (%), V fischeri toxicity (%), P. subcapitata toxicity (%), D. magna Biocompatibility of the SBOs [SBO] (mg/l) [SBO] (mg/l) [SBO] (mg/l) (CVDFT 110 ( ) CVT 230 ( ), FORSUD ( ) 100 mg/l 1 g/l BOD (mg/l) BOD/COD BOD (mg/l) BOD/COD CVDFT CVT FORSUD SBOs should be considered as non-toxic and non biodegradable at the concentrations employed They should not constitute an impostant concern

31 COD (mg/l) COS DOC (mg/l) AOS Photostability of the SBOs: irradiation with H 2 O 2 40 DOC AOS CVDFT 110 CVT 230 FORSUD 0,2 0-0,2-0,4-0,6-0,8-1 -1,2 CVDFT 110 CVT 230 FORSUD Before After Before After COD 1,5 COS CVDFT 110 CVT 230 FORSUD , ,5-1 0 CVDFT 110 CVT 230 FORSUD Before After -1,5 Before After

32 Surface tension BOD/COD E2/E3 Photostability of the SBOs: irradiation with H 2 O 2 BOD/COD 12 E2/E3 0,25 0, ,15 6 0,1 4 0, CVDFT 110 CVT 230 FORSUD Before After Surface tension CVDFT 110 CVT 230 FORSUD Before After 2 0 CVDFT 110 CVT 230 FORSUD Before Results: After Cleavage of the parent macromolecules to form smaller, more oxidized and more hydrophilic ones.

33 Performance of the photo-treated SBOs 1,0 A (FORSUD) 1,0 B (CVDFT 110) 1,0 C (CVT230) 0,8 0,8 0,8 C/C 0 0,6 0,4 C/C 0 0,6 0,4 C/C 0 0,6 0,4 0,2 0,2 0,2 0,0 1, time (min) 0, time (min) 1,0 0, time (min) 1,0 0,8 0,8 0,8 C/C 0 0,6 0,4 C/C 0 0,6 0,4 C/C 0 0,6 0,4 0,2 0,2 0,2 0, time (min) 0, time (min) 0, time (min)