Electrocoagulation and coagulation by iron of latex particles in aqueous suspensions

The goal of coagulation of fine disperse latex particles of suspensions by dosing with iron ions is to enhance suspension clarification, promote sedimentation and improve their filterability. Two kinds of iron dosing were studied; by directly adding iron chloride or iron sulphate to suspensions or by electrolytic decomposition of iron electrodes (electrocoagulation process, EC). The chemical and electrical processes were examined by varying the pH value and the iron ions concentration in order to determine the optimal operating conditions. To minimise the energy consumption in EC, the suspension conductivity and the current density were varied. This paper shows that floes in EC-treated suspensions had a higher density and tended to be larger than floes formed in suspensions dosed with iron chloride or iron sulphate. The kinetics of settling and filtration of EC-treated suspensions were accelerated, demonstrating the interest of EC as an alternative to chemical conditioning. (C) 2002 Elsevier Science B.V. All rights reserved.