Recovery of chromium from plastic plating wastewater by cetyltrimethylammonium bromide MEUF and electrodialysis

Abstract

To study the recovery of chromium for micellar-enhanced ultrafiltration (MEUF) process, a two-stage process was designed to concentrate chromium by MEUF with cetyltrimethylammonium bromide (CTAB), then recovered by electrodialysis (ED). Wastewater from full-scale plant containing heavy metals, including chromium, copper, and nickel, with pH < 2 were tested to investigate the effects of pH, surfactant/metal (S/M) ratio, and operating pressures. The results showed the removal efficiencies of chromate were increased at lower pH and higher CTAB concentration. The micellar hydrodynamic diameters (D_hs) gradually increased with the concentration of CTAB as Cr(VI) of 1.0 mM, and ranged from 3.1 to 4.7 nm. The zeta potentials gradually increased with the concentration of CTAB, but reached plateau for concentration higher than critical micelle concentration. The experimental results indicated that the removal of Cr(VI) by MEUF exceeded 96% for operating parameters of pH 1.53, ΔP = 30 psi, and S/M = 2. For ED process, the effects of current densities and current efficiencies were evaluated as the concentration ratio of 95%, and the chromium was able to pass through anion exchange membrane to recover at the anode side of the ED process up to 85.3% at current density of 20 mA/cm², and operating time of 360 min.

Keywords:

• Chromium
• Cetyltrimethylammonium bromide
• Micellar-enhanced ultrafiltration
• Electrodialysis

Notes

Presented at the Conference on Desalination for the Environment: Clean Water and Energy 11–15 May 2014, Limassol, Cyprus