Using micellar enhanced ultrafiltration and reduction techniques for removal of Cr(VI) and Cr(III) from water

•The maximum reduction of hexavalent chromium was 98.3% by rhamnolipid.•Optimum reduction of Cr(VI) occurred at pH 6 and a rhamnolipid concentration of 2%.•Removal of Cr by rhamnolipid was achieved by reduction followed by MEUF.•Rhamnolipid with MEUF was very effective for removing trivalent chromium from water.•The maximum Cr(III) rejection ratio was 96.2% at 0.1%. rhamnolipid concentration.

Nowadays, hexavalent and trivalent chromium are two forms of heavy metals that have raised a serious concern due to their high toxicity, low biodegradability and carcinogenesis and their ability to pollute groundwater and soil. In this research, reduction and micellar enhanced ultrafiltration (MEUF) methods were used for removing hexavalent and trivalent chromium from water respectively. Rhamnolipid (JBR 425) was also applied as a reducing agent in reduction and a biosurfactant in MEUF techniques because of its low toxicity and biodegradability in the environment. In this study, batch experiments were done in two parts (reduction and MEUF) to investigate the efficiency of rhamnolipid (JBR 425) for removing Cr(VI) and Cr(III). A 10,000 Da polysulfone hollow-fiber membrane, with an area of 140 cm2, was used in MEUF experiments. In the first part of the experiments, initial concentration of hexavalent chromium, pH, and rhamnolipid concentration were examined to observe the effect of these parameters on the reduction of Cr(VI). The maximum reduction of hexavalent chromium was 98.7% at Cr(VI) initial concentration of 10 mg/L, pH 6, and a rhamnolipid concentration of 2% (vol/vol.). In the second part of the trials, the operating factors such as temperature and rhamnolipid concentration in the removal of trivalent chromium and also the behavior of rhamnolipid in the presence of Cr(III) were studied. Temperature had a positive effect on the performance of MEUF system. In all experiments for both parts, it has been illustrated that rhamnolipid (JBR 425) had an extremely good efficiency for removing hexavalent and trivalent chromium from waters which was the main purpose of this research.