Photocatalytic Decolourization of Wastewater from Black Tea (camellia sinensis) Processing Factories using Titanium Dioxide

Abstract

Wastewater from black tea (camellia sinensis) processing factories is characterized by a persistent brick-red colour that conventional treatment works are unable to remove. Forty eight samples each of 500cm³ were collected from three black tea processing factories from western highlands in Kenya and subjected to photocatalytic degradation on Titanium dioxide.

A layer of height of cca 2 cm on TiO₂ in a photocatalytic reactor was illuminated with artificial UV lamp producing radiation at wavelength 365 nm of intensity 3.0 mW/cm² for 3 hours. Another set of experiments was done using solar light of intensity 1.4 mW/cm². Samples of5 cm³ were drawn every 15 minutes and analyzed using UV/Vis spectrophotometer at λ=410 nm.  The results showed that decolourization of 70.4% - 78.5% of the wastewater was achieved in 3 hours. Solar illumination produced higher efficiency of 2.3% above artificial UV lamp irradiation. Decolourization of 59.7% solar and 54.4 % UV lamp was achieved in the first 60 minutes although the solar radiation intensity applied was less than half that of UV lamp.