Enhanced removal efficiency of heavy metal ions from wastewater through functionalized silicon carbide membrane: A theoretical study

Abstract

Development and designing of heavy metal ion separation systems from wastewater play a essential role in environmental protection. For this purpose, in this research, we modeled the synthetic wastewater samples and investigated the capabilities of nano-porous silicon carbide membranes (SiC) with fluorine, nitrogen, and hydroxyl-atom decorated pores under hydrostatic pressures. Increase of applied pressure on SiC with larger pore diameters had more intense effects on water flux and ion rejection. It was also found that, due to different electronic properties of decorated atoms in the edge of pores, which played important roles in their interactions with water molecules and metal ions, as well as energy barrier and permeation, water flux and ion injection were improved. The potential of mean force (PMF) calculation showed that the energy barrier for passing through functionalized pores was higher for metal ions and lower for water molecules. The presence of functional groups in the edge of SiC pores provided selective ion rejection property which was highest for Zn2+ ions. PMF analysis results proved that the PMF values of metal ions were in the following comparative order: SiC@F>SiC@N>SiC@OH>SiC. It was also observed that increase in temperature significantly increased water flux and decreased ion rejection. Also, SiC membrane separation systems improved ion rejection in the presence of electric field along the opposite direction of piston movement, which was more intense in functionalized membranes and results indicated that in voltage of 200 mV/angstrom had the best ion rejection of about 98%.