The self-cleaning hybrid membranes with nano-TiO2 modification for deeply removing the humic acid and heavy metal from water: Mechanism and feasibility

Accumulation of pollutants poses significant challenges to advanced membrane process, impacting efficiency and increasing operational costs. Fulvic acid and its analogues, widely distributed natural organic compounds, degrade water quality and produce by-products in traditional water treatment processes. The presence of even trace heavy metals in water, at the same time, can have a long-term impact on human health. Addressing these issues, we developed a novel TiO 2 -polydopamine (PDA) modified polyvinylidene fluoride (PVDF) membrane (TiO 2 -PDA@PVDF) through an environmental-friendly and low-cost sol-gel method. The membrane features dense nano-TiO 2 coverage, facilitated by a crosslinked dopamine layer, enabling in-situ growth of a functional TiO 2 layer via hydrothermal treatment. This hybrid membrane demonstrates superior adsorption, permeation, and photocatalytic self-cleaning capabilities. Performance analysis demonstrates over 90 % removal efficiency for humic acid and 85–95 % for heavy metals (Tl + , Sb 3+ , and Cr 6+ ). During humic acid separation, the initial flux of nano-TiO 2 membrane was 432 L/m 2 ·h, however, the flux attenuation (63 %) was smaller than unmodified membrane (91 %). Notably, the membrane maintained a flux loss ratio of less than 10 % after multiple operations and self-cleaning cycles, showcasing its robustness and sustainability. The TiO 2 -PDA@PVDF membrane not only effectively intercepts and adsorbs contaminants but also recovers its performance through photo-regeneration facilitated by trace hydrogen peroxide and UV light. These results highlight the membrane's potential for sustainable water purification, presenting a promising solution for both fouling mitigation and enhanced efficiency.