Effect of pH adjustment on wetting mitigation in textile wastewater treatment by membrane distillation

The textile industry has long been associated with significant environmental challenges due to the generation of recalcitrant wastewater, containing complex chemical mixture that pose severe threats to ecosystems and human health. This study focuses on the role of pH adjustment in improving the pretreatment process for direct contact membrane distillation (DCMD) applied to real textile wastewater. By implementing a pH adjustment step (pH 6.14, 7.40, and 9.06) prior to sedimentation and filtration, the pretreatment process was significantly enhanced, reducing wetting, and improving permeate quality. GC–MS analysis identified specific organic molecules causing wetting, including volatile organic acids and alcohol derivatives, revealing that the rejection mechanism is primarily driven by the relationship between the wastewater pH and the pKa of these compounds. Adjusting the pH above the pKa converts these acidic contaminants into ionic, non-volatile forms, effectively preventing their passage into the permeate. This study highlights the importance of pH optimization in advancing DCMD as a sustainable solution for textile wastewater treatment. The proposed approach aligns with circular economy principles, enabling water reuse in textile processes, reducing freshwater consumption, and minimizing environmental discharge.