Eggshell adsorption process coupled with electrocoagulation for improvement of chromium removal from tanning wastewater

Abstract

The present work deals with the removal of trivalent chromium from chrome tanning effluent in a batch stirred electrocoagulation cell with aluminium alloy coupled with biosorption using Eggshell (ES). Effects of operating time, current density and adsorbent dose have been investigated. Compared to a simple electrocoagulation (EC), the concentration of chromium using a coupled or combined EC/ES process has been successfully reduced to environmentally acceptable levels even with a concentrated tanning effluent (3.21 g/L). The maximum uptake of chromium ions was obtained at lower current densities of 200 A/m2, at operating time of 110 min and with the eggshell dose of 12 g/L. The energy consumption during the coupled electrocoagulation/adsorption process was also reduced comparatively to the simple electrocoagulation. A pseudo-second-order chemical sorption model satisfactorily described kinetic data. The water treated by this technique respects the strengths Moroccan standards and the method was found to be highly efficient and relatively fast compared to existing conventional techniques.