Membrane crystallization for recovery of salts from produced water

Membrane Crystallization (MCr) is a novel technology able to recover freshwater and high-purity salts from complex solutions and therefore, is suggested for a better exploitation of wastewater streams. Unlike other membrane processes, MCr is not limited by high concentrations and, therefore, the solutions can be treated to achieve saturation level. Hereby different salts can be precipitated and directly recovered from various streams. In this study, it is shown that MCr is able to treat produced water by producing clean water and simultaneously NaCl crystals. The recovered crystals exhibited high purity. Moreover, the MCr process showed excellent stability in terms of trans-membrane flux during 20 hours of operation. At moderate feed temperature of 47.2 ± 1.7 °C, transmembrane flux of 0.49 ± 0.08 L/(h·m2) was obtained by using commercial hollow fiber membrane module. Throughout the experiments, the membrane maintained its hydrophobic nature despite that produced water contained oil residues. Conductivity and HPLC was utilized to analyze the quality of the permeate stream.