REMOVAL OF ORGANIC MICROPOLLUTANTS FROM DRINKING WATER BY ELECTROCHEMISTRY

Transcription

1 REMOVAL OF ORGANIC MICROPOLLUTANTS FROM DRINKING WATER BY ELECTROCHEMISTRY EXPERIENCES OBTAINED WITH PESTICIDE RESIDUE BAM JENS MUFF, ASSISTANT PROFESSOR CO-AUTHORS: HENRIK T. MADSEN & ERIK G. SØGAARD

2 Outline Motivation of study Electrochemical Advanced Oxidation (EAOP) Lab scale Proof-of-concept in drinking water The influence of water composition on fate of BAM during EAOP Conclusion SECTION OF CHEMICAL ENGINEERING 2

3 Occurrence of pesticides in DK groundwater and drinking water 25% Percentage of Danish drinking water found to contain pesticides BAM (2,6-dichlorobenzamid) Places in Denmark where pesticides have been found in groundwater and drinking water (small private wells not shown) Thorling, L., Brüsch, W., Hansen, B., Larsen, C.L., Mielby, S., Troldborg, L. og Sørensen, B. L., 2013: Grundvand. Status og udvikling Teknisk rapport, GEUS ISBN SECTION OF CHEMICAL ENGINEERING 3

4 Effect of existing technology on pesticides and residues Sandfiltration Before (ng/l) After (ng/l) BAM Desisopropylatrazine Desethylatrazine Simazine Atrazine Diurone Mechlorprop Søgaard et al. (2001). Applied Geochemistry, 16, Kowalski KP, Madsen HT and Søgaard EG (2014). Water Science & Technology: Water Supply, 14, SECTION OF CHEMICAL ENGINEERING 4

5 Current solution Activated Carbon adsorption AC adsorption is a suitable method for removal of BAM from groundwater. The capacities for BAM are in the same order of magnitude as capacities for Atrazine. (Despite being more hydrophilic). Clausen et al. Miljøprojekt Nr Bench scale tests on Atrazine and BAM at Hvidovre water work SECTION OF CHEMICAL ENGINEERING 5

6 EAOP as a potential alternative Anode + Reduction Oxidation Polluted water Power supply Cathode PROs of EAOP Environmental compatible technique: use of a clean reagent (the electron), no addition of excess chemicals, Control of reaction rate: Through control of applied current. the process can be turned on and off Amenability to automation: Simple to operate and automate Versatile: non-selective towards a wide range of organic pollutants Less independent of temperature: Compared to chemical oxidation SECTION OF CHEMICAL ENGINEERING 6

7 Reaction mechanisms in EAOP Active oxygen formation MO + H + (chemi-sorption) M( OH) + H + (physi-sorption) e - e - Direct oxidation R R H 2 O e - EOTR* R -Pt-Pt-Pt-Pt-Ir-Pt-Pt-Pt-Pt- ROH / RO CO 2 + H 2 O * EOTR = Electrochemical oxygen transfer reaction (EOTR) 7 Source: Muff et al. (2010) Nova Science P bli h

8 Reaction mechanisms in EAOP Active oxygen formation MO + H + (chemi-sorption) M( OH) + H + (physi-sorption) e - e - Direct oxidation R R H 2 O e - EOTR* R -Pt-Pt-Pt-Pt-Ir-Pt-Pt-Pt-Pt- ROH / RO CO 2 + H 2 O e - Indirect mediated oxidation 2Cl - Cl - Cl 2 + H 2 O HOCl + H + + Cl - CO 2 + H 2 O R * EOTR = Electrochemical oxygen transfer reaction (EOTR) 8

9 Electrochemical oxidation of BAM in drinking water BAM 0 = 10 mg L -1 ; j = 10 ma cm -2 k = min -1 k = min -1 k = min -1 Madsen HT, Søgaard EG and Muff J (2015). In preparation. SECTION OF CHEMICAL ENGINEERING 9

10 Model studies influence of ions (in Na 2 SO 4 ) Amount of degradation intermediates/byproducts Conc. vs. time Origin of carbon BAM BDD anode TOC Pt anode SECTION OF CHEMICAL ENGINEERING From Madsen HT, Søgaard EG and Muff J (2014). Chemosphere, 109,

11 Model studies influence of ions (in Na 2 SO 4 ) Amount of degradation intermediates/byproducts Development in intensity Reaction pathway SECTION OF CHEMICAL ENGINEERING From Madsen HT, Søgaard EG and Muff J (2014). Chemosphere, 109,

12 Model studies influence of ions (in NaCl) Type of DIs/ byproducts From Madsen HT, Søgaard EG and Muff J (2015). Chemosphere, 120, SECTION OF CHEMICAL ENGINEERING 12

13 Model studies influence of ions (in NaCl) Amount of DIs/ byproducts In Na 2 SO 4 In NaCl

14 Conclusions BAM in drinking water is efficiently degraded by EAOP Degradation pathways are complex but full mineralization can be obtained EAOP is a versatile technique, analogue studies have been made on most pesticides EAOP can be considered an alternative to other AOPs and AC SECTION OF CHEMICAL ENGINEERING 14

15 Thank you for your attention References: Study of degradation intermediates formed during electrochemical oxidation of pesticide residue 2,6-dichlorobenzamide (BAM) in chloride medium at boron doped diamond (BDD) and platinum anodes. / Madsen, Henrik Tækker; Søgaard, Erik Gydesen; Muff, Jens. I: Chemosphere, Vol. 120, p Study of the degradation intermediates formed during electrochemical oxidation of pesticide residue 2,6-dichlorobenzamide (BAM) at boron doped diamond (BDD) and platinum-iridium anodes. / Madsen, Henrik Tækker; Søgaard, Erik Gydesen; Muff, Jens. I: Chemosphere, Vol. 109, , s SECTION OF CHEMICAL ENGINEERING 15