Simple and Low-Cost Electroactive Membranes for Ammonia Recovery.

Ammonia is considered a contaminant to be removed from wastewater. However, ammonia is a valuable commodity chemical used as the primary feedstock for fertilizer manufacturing. Here we describe a simple and low-cost ammonia gas stripping membrane capable of recovering ammonia from wastewater. The material is composed of an electrically conducting porous carbon cloth coupled to a porous hydrophobic polypropylene support, that together form an electrically conductive membrane (ECM). When a cathodic potential is applied to the ECM surface, hydroxide ions are produced at the water-ECM interface, which transforms ammonium ions into higher-volatility ammonia that is stripped across the hydrophobic membrane material using an acid-stripping solution. The simple structure, low cost, and easy fabrication process make the ECM an attractive material for ammonia recovery from dilute aqueous streams, such as wastewater. When paired with an anode and immersed into a reactor containing synthetic wastewater (with an acid-stripping solution providing the driving force for ammonia transport), the ECM achieved an ammonia flux of 141.3 ± 14.0 g.cm-2.day-1 at a current density of 6.25 mA.cm-2 (69.2 ± 5.3 kg(NH3-N)/kWh). It was found that the ammonia flux was sensitive to the current density and acid circulation rate.

Possibility assessment of ultrafiltration membrane pre-treatment efficiency for brackish water reverse osmosis-based wastewater reuse: Lab and demonstration.

Ultrafiltration (UF) membranes are considered a pre-treatment for brackish water reverse osmosis (BWRO) membranes because of the high rejection rate of particulates and the productivity of the final water quantity. This study presents the performance and membrane surface property analysis of UF membranes for commercial membrane manufacturers, and their structural strength and chemical resistance were evaluated. Moreover, the pilot-scale UF-BWRO process was operated for two months using real wastewater based on the results of this study. Although the overall properties were similar, the poly (ether-sulfone) UF membrane showed higher tensile strength than the polyvinylidene difluoride and polyacrylonitrile UF membranes. The UF membrane showed a high removal rate of particulates (over 90%) but low rejection rate of organic compounds, such as humic acid and sodium alginate (below 30%). After exposure to high concentrations of chemicals, the contact angle of the membranes was reduced by approximately 15% compared to that of the virgin membranes. In addition, despite the exposure to low-and high-concentration chemicals, UF membranes were relatively stable in terms of tensile strength. During the operation period of the pilot-scale UF-RO process, the UF membrane showed a high turbidity removal of over 93%, and the UF-BWRO process presented a high salt rejection of over 92%. The UF membrane showed potential for the pre-treatment of BWRO membranes.