Analysis of membrane performance in Ni and Co removal from liquid wastes by means of micellar-enhanced ultrafiltration

Abstract

Heavy metal pollution of civil and industrial wastewaters represents a major problem for the environment since metal ions are non-biodegradable, have a very high toxicity, and some of them have proved to be carcinogenic. If directly discharged in sewers, metal ions may seriously damage the subsequent biological treatments in depuration plants and render treatment sludge not reusable for agriculture. On the contrary, water and sludge reuse should be a primary criterion when planning improvements for wastewater treatment plants and their adaptation to new standards. In this paper, the membrane performance (a monotubular ceramic membrane of molecular weight cutoff: 210 kDa) is investigated in the removal of nickel and cobalt ions from synthetic liquid wastes aimed at water reuse using a micellar-enhanced ultrafiltration process. The ultrafiltration membrane is used with adding an anionic surfactant (sodium dodecyl sulfate (SDS)) in a laboratory scale experimental device. The synthetic liquid waste contains metal ions in a concentration range 10–100 mg/L, and the SDS concentration was 1.15 mg/L, under the critical micellar concentration (CMC). The experiments have been carried out at a fixed temperature of 20°C. The preliminary results show that very good percentage removals of these metal ions are achieved, even if the surfactant was below its CMC.