Double-diamine thin film composite nanofiltration membrane for sulfate removal

The oil and gas activities such as hydraulic fracturing requires huge quantities of sulfate-free water. The objective of this study is to design a membrane that can selectively remove sulfates from seawater. The membrane was developed by interfacial polymerization of an aqueous mixture of two diamines (TTDA and PIP) with an organic solution of TMC. The merits of the prepared membranes were characterized by a cross-flow permeation setup and evaluated under different operating pressures and temperatures. The optimum membrane (at 50%TTDA) achieved a permeate flux of 53 L/m2.h and a sulfate rejection of 96%. The permeate flux can be increased significantly by increasing either the operating pressure or temperature. However, this will be accompanied by significant reduction in the sulfate rejection. This study shows that the permeation properties can be altered and designed for a specific application by introducing a second monomer (such as the TTDA) in the aqueous diamine solution.