Pulp and Paper Effluent Treatment and Detoxification: Photo Catalytic Degradation of Methylene Blue Using Natural Ultra-Violet Light and Titanium Oxide
Abstract
Pulp and paper mill effluent treatment and detoxification methods have been extensively investigated resulting to varying efficiencies and capital and operational costs. The main toxic component in the mills’ effluent is modified lignin, which is difficult to degrade by convectional effluent treatment systems applied by most mills. This study aimed at using natural photo catalytic degradation of methylene blue using anodised pigmented and non-pigmented titanium plates to optimise anodising time and voltage. Titanium plates were anodised at varying voltages and times in a mixture of sulphuric and hydrofluoric acids. Irradiation of aqueous solution of methylene blue was done using varies anodised pigmented and non pigment plates in a batch reactor cell. Absorbance of each photo catalysed solution was determined every five minutes after a dark phase of fourteen minutes using a laser light source. Absorbance was then converted to transmittance, which gave photo catalytic reactivity of plates. The study revealed that photo catalytic reactivity of pigmented titanium plates was higher than non-pigmented. Photo catalytic reactivity also increased with increase in anodising time and voltage. Anodised plate at 200volts for 120 seconds and pigmented with photo catalytic reactivity of 62.325 x 10-3 was found to be the best to degrade methylene blue. Application of this optimised plate on Kraft Pulp mill effluent showed reduction in COD, BOD, turbidity, colour and total suspended solids. However effluent pH and electrical conductivity increased. COD, BOD, turbidity and colour removal efficiency improved on introduction of wood ash leachate (electrolyte) in photo catalytic activity. The study recommended the use anodised titanium plates using natural ultra violet energy aid by an electrolyte to treat Kraft pulp and paper mill effluent.