Use of rhamnolipid to remove heavy metals from wastewater by micellar-enhanced ultrafiltration (MEUF)

In this research, the rhamnolipid biosurfactant was utilized in micellar-enhanced ultrafiltration (MEUF) of heavy metals from contaminated waters. The effects of different major operating conditions on the (MEUF) system performance were investigated for copper, zinc, nickel, lead and cadmium using two membranes. The optimal conditions were successfully applied to treat six contaminated wastewaters from metal refining industries using the two membranes (>99% rejection ratio). To efficiently choose the most influential factors to the MEUF system, optimization by the response surface methodology approach was utilized and data quality was examined.Optimization by the response surface methodology and validation experiments determined that the best operating conditions were a transmembrane pressure of 69 ± 2 kPa, biosurfactant-to-metal molar ratios of approximately 2:1, a temperature of 25 ± 1 °C, and pH of 6.9 ± 0.1. The rhamnolipid-enhanced ultrafiltration system was also to shown to treat samples of six contaminated wastewaters from metal refining industries using membranes with molecular weight cutoffs (MWCO) of 10,000 Da and 30,000 Da. The resulting heavy metal concentrations in the permeate were all significantly reduced to be in accordance with the federal Canadian regulations.

Schematic diagram of micelle-enhanced ultrafiltration of metal-contaminated wastewater.Figure optionsDownload as PowerPoint slideResearch highlights▶ MEUF could treat six metal contaminated wastewaters with rejection ratios of >99%. ▶ Optimal MEUF conditions were obtained at biosurfactant-to-metal molar ratios of 2:1. ▶ Optimal conditions were at a transmembrane pressure of 69 kPa, 25 °C and pH 6.9. ▶ The UF membranes showed the lowest fouling tendency at 73% water recovery. ▶ The permeate heavy metal concentrations were reduced to federal Canadian regulations.