A fixed bed electrochemical cell was tested as reactor for treatment of waters by 12 direct electrolysis. The aim was the development of a reactor configuration for 13 effective and controllable primary and secondary disinfection. Stacks of titanium 14 grids coated with Ru/Ir oxides or platinum were used as anodes and cathodes, 15 respectively. The electrode packings were arranged in series, the system worked 16 in continuous mode. 17 The reactor was characterised for mass transfer (by the limiting current densities 18 technique) and flow behaviour (by pulse-response curves with an inert tracer). 19 Electrolyses were carried out with 100 mg dm-3 of chloride ions, and current 20 density ranging from 2.5 to 7.5 mA cm-2. 21 Active chlorine concentrations from 0.3 to 1.2 mmol dm-3 were obtained in the 22 reactor outlet, depending on the conditions. The higher value was measured with 23 i = 7.5 mA cm-2 and flow conditions corresponding to a Reynolds number of 5: 24 under these conditions, about 1 mg dm-3 of chlorates were detected, otherwise 25 the selectivity of the process towards active chlorine was about unit. 26 A mathematical model at steady state was implemented, and pseudo first order 27 kinetics was used to describe chemical and electrochemical reactions. The 28 model allowed obtaining the concentration profiles of chloride and chloride 29 oxidation by-products which were compared with experimental data, with good 30 agreement in a wide range of flow rates. The configuration allowed a well-defined 31 concentration profile: the active chlorine in the outlet was always 50% less than 32 the value inside the reactor, allowing to exploit the process for primary and 33 secondary disinfection.
Fixed bed reactors with three dimensional electrodes for electrochemical treatment of waters for disinfection
MASCIA, MICHELE;VACCA, ANNALISA;PALMAS, SIMONETTA
2012-01-01
Abstract
A fixed bed electrochemical cell was tested as reactor for treatment of waters by 12 direct electrolysis. The aim was the development of a reactor configuration for 13 effective and controllable primary and secondary disinfection. Stacks of titanium 14 grids coated with Ru/Ir oxides or platinum were used as anodes and cathodes, 15 respectively. The electrode packings were arranged in series, the system worked 16 in continuous mode. 17 The reactor was characterised for mass transfer (by the limiting current densities 18 technique) and flow behaviour (by pulse-response curves with an inert tracer). 19 Electrolyses were carried out with 100 mg dm-3 of chloride ions, and current 20 density ranging from 2.5 to 7.5 mA cm-2. 21 Active chlorine concentrations from 0.3 to 1.2 mmol dm-3 were obtained in the 22 reactor outlet, depending on the conditions. The higher value was measured with 23 i = 7.5 mA cm-2 and flow conditions corresponding to a Reynolds number of 5: 24 under these conditions, about 1 mg dm-3 of chlorates were detected, otherwise 25 the selectivity of the process towards active chlorine was about unit. 26 A mathematical model at steady state was implemented, and pseudo first order 27 kinetics was used to describe chemical and electrochemical reactions. The 28 model allowed obtaining the concentration profiles of chloride and chloride 29 oxidation by-products which were compared with experimental data, with good 30 agreement in a wide range of flow rates. The configuration allowed a well-defined 31 concentration profile: the active chlorine in the outlet was always 50% less than 32 the value inside the reactor, allowing to exploit the process for primary and 33 secondary disinfection.
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