Simultaneous retention of organic and inorganic contaminants by a ceramic nanofiltration membrane for the treatment of semiconductor wastewater

The semiconductor manufacturing industry produces large amounts of ammonia-contaminated wastewaters which require costly and energy-intensive treatments. This study demonstrates the application of a commercially available ceramic nanofiltration (NF) membrane for the control of organic and inorganic contaminants as well as ammonium retention in the treatment of semiconductor wastewater. Analysis of the hydrodynamic pore transport model based on the direct measurement of membrane thickness in the active layer indicated that the ceramic NF membrane has an average pore radius of ≈0.65 nm. Zeta potential measurements of the ceramic NF membrane showed that the membrane surface was negatively charged at neutral pH. The ammonium retention capacity of the ceramic NF membrane was evaluated using a single symmetric ammonium salt solution (1.8 mM NH4HCO3; i.e., the average ammonium concentration in semiconductor wastewater) and combined salt solutions (mixtures of 1.8 mM NH4HCO3 and either 2.0 mM of Na2SO4, CaSO4, or CaCl2). The combined NH4HCO3 and Na2SO4 solution rendered a remarkably high ammonium retention rate of 88.7%, which was attributed to higher valency co-ions (SO42-) in this solution with the same negative surface charge of the ceramic NF membrane. In contrast, the calcium ions (Ca2+) in different combined salt solutions containing CaSO4 and CaCl2 interfered with ammonium retention. We further employed the ceramic NF membrane to treat semiconductor wastewater samples taken from a full-scale semiconductor wastewater treatment plant and demonstrated that this proposed treatment method could effectively retain organic and inorganic contaminants with a low fouling propensity. Our results highlight the promising potential of ceramic NF membranes for the treatment of industrial wastewaters with diverse organic and inorganic contaminants.