*J. Prko , **H. C. B. Hansen and *T. Weidlich *Institute of - - PowerPoint PPT Presentation

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*J. Prko , **H. C. B. Hansen and *T. Weidlich *Institute of - - PowerPoint PPT Presentation

Oct 08, 2022 327 likes •483 views

*J. Prko , **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

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*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

  • f

Science, University

  • f

Copenhagen

*J. Pérko, **H. C. B. Hansen and *T. Weidlich

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O OH Cl 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.
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  • 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.

O OH Cl Cl Cl O OH X X X 1a - X = 2x Cl, 1x H Al-Ni alloy / Devarda's alloy / Arnd's alloy Base (NaOH / KOH / Na2CO3 / NH4OH etc.) 1 1b - X = 1x Cl, 2x H 1c - X = 3x H

* *

O H Cl O H Cl

  • Reductive dechlorination of triclosan 1 and other

chlorinated aromatics* by metal alloys (Al-Ni, Devarda’s alloy, Arnd’s alloy).

OH Cl

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Electrochemical advanced oxidation processes (EAOPs) based

  • n Fenton’s reaction chemistry

Electrogeneration of H2O2 at the cathode Addition of H2O2 directly to the reaction or its indirect generation Electro-Fenton (EF) process Combined EF processes Electrochemical Fenton processes Combined Fenton processes One or two- compartment cells Iron catalyst (Fe2+, Fe3+ or iron oxide) cathode, anode

  • Photo assisted EF:

Photoeletro-Fenton, Solar photoeletro- Fenton,etc.

  • Sonoelectro-Fenton
  • Cathodic generation
  • f Fe2+
  • Ferred Fenton

process

  • Electrochemic

al peroxidation process

  • Anodic Fenton

treatment

  • Photo

combined processes

  • Indirect

H2O2 production

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Electrochemical advanced oxidation processes (EAOPs) based

  • n Fenton’s reaction chemistry

Electrogeneration of H2O2 at the cathode Addition of H2O2 directly to the reaction or its indirect generation Electro-Fenton (EF) process Combined EF processes Electrochemical Fenton processes Combined Fenton processes One or two- compartment cells, iron catalyst (Fe2+, Fe3+ or iron oxide) cathode, anode

  • Photo assisted EF:

Photoeletro-Fenton, Solar photoeletro- Fenton,etc.

  • Sonoelectro-Fenton
  • Cathodic generation
  • f Fe2+
  • Ferred Fenton

process

  • Electrochemic

al peroxidation process

  • Anodic Fenton

treatment

  • Photo

combined processes

  • Indirect

H2O2 production

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SLIDE 6

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etc. etc. etc.

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2 - Electrolytic cell:

  • Ti/RuO2-IrO2 as cathode & anode in PP container.
  • Surface area: 165 cm2
  • 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 (Na2SO4 or NaCl, Fe2+). 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:H2O (65:35, v/v); flow rate 1 ml/min. Soluble and total soluble iron were measured by the 1,10-phenantroline method.

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Sorption PTFE tubing Pump tubing PTFE pump tubing Available kinds

  • f plastic tubing

Special PTFE pump head Expensive!!! Special pump tubing with zero sorption VERY expensive!!! Sorption Time consuming, not precise H2O2 determination Available methods Spectrophotometric methods Iodine method 2,9- dimethylphenantroli ne method Metavanadate method Test in near future Strong interference with iron (Fe2+, Fe3+) and possibly even small interference with TCS

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5 10 15 20 25 0mM Na2SO4 2mM Na2SO4 10mM Na2SO4 20mM Na2SO4 10mM NaCl Percentage of sorption [%]

Concentration of supporting electrolyte effect on sorption

Aim to „standardize“ the sorption phenomenon by sorption tests and then deduct these values from experiments with current going through electrolysis cell to get the degradation

  • f TCS alone.

10 20 30 40 50 60 No Fe2+, 4 mM Na2SO4 No Fe2+, 20 mM Na2SO4 5 mg/l Fe2+, 2 mM Na2SO4 5 mg/l Fe2+, 20 mM Na2SO4 50 mg/l Fe2+, 2 mM Na2SO4 50 mg/l Fe2+, 20 mM Na2SO4

Percentage of degradation [%]

Effect of iron(II) and supporting electrolyte concentrations at current density 24 mA/cm^2

5 10 15 20 25 30 35 40 45 6 mA/cm^2 12 mA/cm^2 24 mA/cm^2 Percentage of degradation [%]

Effect of current density on degradation 9

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SLIDE 10

10 20 30 40 50 60 70 80 10 20 30 40 50

Soluble Fe(II), 2 mM Na2SO4 Total soluble iron, 2 mM Na2SO4 Soluble Fe(II), 20 mM Na2SO4 Total soluble iron, 20 mM Na2SO4

time [min] Soluble Fe

2+ [mg/l]

Time course of concentration of iron(II) and total soluble iron with 2 and 20 mM Na2SO4, 50 mg/l Fe(II), 10 mg/l TCS, I=4A

5 10 15 20 25 30 35 pH 4 pH 3 Percentage of degradation [%]

Effect of pH on degradation

5 10 15 20 25 30 35 Degradation Sorption

Percentage of sorption & degradation [%]

Effect of flow rate on degradation and sorption

50 ml/min 100 ml/min

10 20 30 40 50 60 1 2 3 4 5

Time course of concentration of iron(II) and total soluble iron with 2 and 20 mM Na2SO4, 50 mg/l Fe(II), 10 mg/l TCS, I=4A

Soluble Fe(II), 2 mM Na2SO4 Total souble iron, 2 mM Na2SO4 Soluble Fe(II), 20 mM Na2SO4 Total souble iron, 20 mM Na2SO4

time [min] Soluble Fe

2+ [mg/l]

10

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HPLC chromatogram of reaction mixture after 2 minutes HPLC chromatogram of reaction mixture after 4 minutes HPLC chromatogram of reaction mixture after 20 minutes

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  • Degradation of TCS in aqueous solution at acidic pH by electrolysis unit equipped

with Ti/RuO2-IrO2 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.

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  • 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.

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Supervisor Tomáš Weidlich Supervisor Hans Christian Bruun Hansen All the people from Section of Environmental Chemistry and Physics

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