Indian Journal of Chemical Technology, Vol.13, No.3, 262-268, 2006
Removal of total dissolved solids with simultaneous recovery of acid and alkali using bipolar membrane electrodialysis - Application to RO reject of textile effluent
The present paper focuses on the application of electrodialysis process with bipolar membranes (EDBPM) for the treatment of reverse osmosis (RO) reject. The purpose of this work includes investigation on the reduction of total dissolved solids (TDS) of the RO reject process with the recovery of acids and bases. Preliminary studies were conducted with sodium chloride solutions in batch recirculation mode. The effect of process parameters such as electrolyte concentration in the electrode compartments (sulphuric acid and NaOH in anode and cathode compartments respectively), current density, flow rate, feed concentration on the process efficiency such as acid and alkali production, current efficiency and energy consumption were evaluated. The transport of co-ions to the electrode compartments was also studied. The Optimum conditions of the process were found to be with electrolytes of 0.05 N concentration in electrode compartments (sulphuric acid and sodium hydroxide in anode and cathode, compartments, respectively), with current density of 0.83A/ dm(2) at 10, 000 mL/h flow rate. At these conditions the treatment was applied to a RO reject of textile effluent for the removal of TDS with acid and alkali recovery. On treatment the conductivity of the solution decreased to about 99.6% with recovery of acid and alkali concentrations of 0.274 N and 0.258 N, respectively. The energy consumption and current efficiency of the process were found to be 0.310 KWh/L and 56.8%, respectively. The transport number of chloride and sodium ions during the treatment of RO reject was found to be 0.0389 and 0.0161, respectively.
Keywords:electrodialysis;bipolar membranes;textile dye effluent;RO reject;TDS removal;acid/alkali recovery