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Electrocoagulation method for colour removal in tea effluent: a case study of Chemomi tea factory in rift valley, Kenya

Author(s): Justin K. Maghanga | Fred K. Segor | Lazare Etiégni | John Lusweti

Journal: Bulletin of the Chemical Society of Ethiopia
ISSN 1011-3924

Volume: 23;
Issue: 3;
Start page: 371;
Date: 2009;
Original page

Keywords: Tea effluent | Electrochemical | Phenol coupling | Radicals | Colour removal | Theaflavins

A simple and efficient electrochemical method that utilizes two steel electrodes and is capable of reducing the colour of tea effluent prior to its discharge into the river system has been developed. The effects of potential difference, inter-electrode distance, surface area of electrodes to effluent volume ratio (S/V), effluent pH, temperature and effluent dilution on power consumption, were investigated. This method was effective at a potential difference of 24 volts, inter-electrode distance of 5 mm, S/V of 18.2 m2/m3 and effluent pH of 6. Effluent dilution led to increase in power consumption while raising temperatures led to a reduction in power consumption. Electrochemical method reduced COD, BOD and electrical conductivity by 96.6 %, 84.0 % and 31.5 %, respectively but increased pH by 10.32 %. The final pH, EC, COD and BOD values were below KBS maximum contaminant levels. The proposed mechanism in colour removal process was phenol coupling. Phenolic tea colour pigments were oxidized by electrons from ionization of iron to form keto radicals, which polymerized to form a long chain polymer. The polymer was electro-floated to the surface by hydrogen gas generated from the reduction of water and oxidation of theaflavins.
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