Removal of benzidine based textile dye using different metal hydroxides generated in situ electrochemical treatment-A comparative study

Abstract

Benzidine is used as an intermediate compound for the production of many types of dyes and it is found to be carcinogenic to human. The use of benzidine dyes are significantly withdrawn in most of the industries, but still it is used as colorant to dye the fabrics. The present study focuses on the treatment efficiency of electrochemical process in the removal of benzidine based triazo dye namely C.I. Direct Green 1 (DG1). Various key process parameters are employed to analyses the efficiency of ferrous and aluminum hydroxides on removal of colour is observed as 99.10%, chemical oxygen demand (COD) of dye solution observed as 75.71 and 89.65% for stainless steel (SS) and aluminum (Al) electrodes. The process efficiency is analyzed by observing the variation of pseudo first order kinetic rate constant values of 0.115 and 0.256 min−1, energy and electrode consumptions are found as 1.50 kWh/kg dye, 0.75 kWh/kg dye and 0.31 kg Fe/kg, 0.06 kg Al/kg dye for SS and Al electrodes respectively. The dye removal mechanism with metal hydroxides is observed as the partial degradation of azo bonds and followed by sweep coagulation with iron hydroxides/oxyhydroxides and charge neutralization with aluminum hydroxides/oxyhydroxides are supported by UV–visible, Fourier Transform Infrared (FTIR) and Scanning Electron Microscope and Energy Dispersive X-Ray (SEM-EDX) spectroscopy analysis of treated water and electrocoagulated flocs. Finally, the cost of electrocoagulation is evaluated for treatment of DG1 and it is identified to be 1.89$/kg dye for SS electrodes and 0.78$/kg dye for Al electrodes.