*J. Pérko , **H. C. B. Hansen and *T. Weidlich *Institute of environmental and chemical engineering, Faculty of chemical technology, University of Pardubice **Section of environmental chemistry and physics, Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen
Cl OH O Cl Cl • Polychlorinated aromatic compound. • Antibacterial agent. • Overuse bacteria resistance. • Wastewater treatment plants (WWTP) overload causing trace concentrations on outlets toxicity for water organisms (e.g. algae, daphnids, fish, … ). • Restricted in cosmetic products by EU since 2014. 2
• Reductive dechlorination of triclosan 1 and other H O * H O chlorinated aromatics* by metal alloys (Al-Ni, OH Cl Devarda ’s alloy, Arnd’s alloy). * Cl Cl Cl OH X OH O Al-Ni alloy / Devarda's alloy / Arnd's alloy O Base (NaOH / KOH / Na 2 CO 3 / NH 4 OH etc.) Cl Cl X X 1a - X = 2x Cl, 1x H 1 1b - X = 1x Cl, 2x H 1c - X = 3x H • Can we use Advanced oxidation processes (AOP’s)? Generation of • OH radicals as powerful oxidants. Fenton oxidation Cooperation with Adept Water Technologies A/S which supplied electrolysis cell. Electro-Fenton process for TCS degradation. 3
Electrochemical advanced oxidation processes (EAOPs) based on Fenton’s reaction chemistry Electrogeneration of H 2 O 2 at Addition of H 2 O 2 directly to the the cathode reaction or its indirect generation Electrochemical Combined Electro-Fenton Combined EF Fenton Fenton (EF) process processes processes processes One or two- • Photo assisted EF: compartment • Ferred Fenton • Photo cells Photoeletro-Fenton, process combined Iron catalyst • Electrochemic Solar photoeletro- processes (Fe 2+ , Fe 3+ or Fenton,etc. al peroxidation • Indirect • Sonoelectro-Fenton iron oxide) process H 2 O 2 • Cathodic generation cathode, • Anodic Fenton production anode of Fe 2+ treatment 4
Electrochemical advanced oxidation processes (EAOPs) based on Fenton’s reaction chemistry Electrogeneration of H 2 O 2 at Addition of H 2 O 2 directly to the the cathode reaction or its indirect generation Electrochemical Combined Electro-Fenton Combined EF Fenton Fenton (EF) process processes processes processes One or two- • Photo assisted EF: • Ferred Fenton • Photo compartment Photoeletro-Fenton, process cells, combined • Electrochemic Solar photoeletro- iron catalyst processes Fenton,etc. al peroxidation (Fe 2+ , Fe 3+ or • Indirect • Sonoelectro-Fenton process iron oxide) H 2 O 2 • Cathodic generation • Anodic Fenton cathode, production of Fe 2+ treatment anode 5
etc. etc. etc . 6
2 - Electrolytic cell: - Ti/RuO 2 -IrO 2 as cathode & anode in PP container. - Surface area: 165 cm 2 - Distance between electrodes: 1,6 mm 3 - Peristaltic pump – flow rate 50 and 100 ml/min 4 – 10 mg/l TCS aqueous solution, pH = 3 or 4 (Na 2 SO 4 or NaCl, Fe 2+ ). 6 - PTFE tubing - no sorption, plastic pump tubing - sorption of TCS Analysis: Agilent Technologies HPLC 1100/1200 series - Zorbax Eclipse XDB - C18 column (4.6 x 150 mm, 5 μm) ; DAD detector ( λ =214, 220 nm; mobile phase: ACN:H 2 O (65:35, v/v); flow rate 1 ml/min. Soluble and total soluble iron were measured by the 1,10-phenantroline method. 7
H 2 O 2 determination Sorption Available methods PTFE tubing Spectrophotometric Pump tubing methods Special pump Available kinds PTFE pump tubing Iodine tubing with of plastic tubing method zero sorption 2,9- Special PTFE Sorption dimethylphenantroli VERY expensive!!! pump head ne method Time consuming, Expensive!!! Metavanadate not precise method Strong interference with iron (Fe 2+ , Test in near Fe 3+ ) and possibly even small future interference with TCS 8
Concentration of supporting electrolyte effect on sorption Aim to „standardize“ the 25 sorption phenomenon by Percentage of sorption [%] 20 sorption tests and then deduct these values from 15 experiments with current 10 going through electrolysis 5 cell to get the degradation of TCS alone. 0 0mM Na2SO4 2mM Na2SO4 10mM Na2SO4 20mM Na2SO4 10mM NaCl Effect of iron(II) and supporting Effect of current density on degradation electrolyte concentrations at current 45 density 24 mA/cm^2 40 60 Percentage of degradation [%] Percentage of degradation [%] 35 50 30 40 25 30 20 20 15 10 10 0 5 No Fe2+, No Fe2+, 5 mg/l 5 mg/l 50 mg/l 50 mg/l 4 mM 20 mM Fe2+, 2 Fe2+, 20 Fe2+, 2 Fe2+, 20 0 Na2SO4 Na2SO4 mM mM mM mM 6 mA/cm^2 12 mA/cm^2 24 mA/cm^2 Na2SO4 Na2SO4 Na2SO4 Na2SO4 9
Time course of concentration of iron(II) and total soluble iron with Effect of pH on degradation 2 and 20 mM Na 2 SO 4 , 50 mg/l Fe(II), 10 mg/l TCS, I=4A 50 35 Percentage of degradation [%] 30 Soluble Fe(II), 2 mM Na 2 SO 4 40 Total soluble iron, 2 mM Na 2 SO 4 Soluble Fe(II), 20 mM Na 2 SO 4 25 Total soluble iron, 20 mM Na 2 SO 4 2+ [mg/l] 30 20 Soluble Fe 15 20 10 10 5 0 0 0 10 20 30 40 50 60 70 80 pH 4 pH 3 time [min] Time course of concentration of iron(II) and total soluble iron with Effect of flow rate on degradation and 2 and 20 mM Na 2 SO 4 , 50 mg/l Fe(II), 10 mg/l TCS, I=4A sorption 5 35 Percentage of sorption & degradation [%] 30 4 50 ml/min Soluble Fe(II), 2 mM Na2SO4 25 Total souble iron, 2 mM Na2SO4 2+ [mg/l] Soluble Fe(II), 20 mM Na2SO4 3 Total souble iron, 20 mM Na2SO4 100 ml/min 20 Soluble Fe 15 2 10 1 5 0 0 0 10 20 30 40 50 60 Degradation Sorption time [min] 10
HPLC chromatogram of reaction mixture after 2 minutes HPLC chromatogram of reaction mixture after 4 minutes HPLC chromatogram of reaction mixture after 20 minutes 11
• Degradation of TCS in aqueous solution at acidic pH by electrolysis unit equipped with Ti/RuO 2 -IrO 2 electrodes has been studied. • Using for the purpose of TCS breakdown is possible. • High sorption of TCS to plastic parts of the experimental setup. • Electro-Fenton or some different kind of phenomenon occurring during experiments? Possible direct oxidation on electrodes? • Quite slow degradation rate of triclosan. • Using of NaCl as supporting electrolyte generates powerful oxidizing agents – an alternative to Fenton reagents. • Future focus of research on intermediates analysis and finding suitable method for determination of hydrogen peroxide. 12
Supervisor Hans Christian Bruun Hansen All the people from Section of Superviso r Tomáš Weidlich Environmental Chemistry and Physics 13
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