Fine bubble-mediated alkaline micro-interface: A novel strategy for enhanced coagulation in sustainable drinking...

Cleaner production of drinking water is a core global endeavor for advancing sustainable development, with enhanced coagulation serving as a pivotal technology to reconcile treatment efficiency with environmental sustainability. An innovative interface-regulated coagulation strategy was proposed herein, based on a fine bubble-assisted co-coagulation process that integrated enhanced coagulation with cleaner production objectives through the construction of an alkaline micro-interface and the regulated forced hydrolysis of polymeric aluminum chloride (PACl). The structure-activity correlations among PACl hydrolysis characteristics, solution potential environment, and target pollutant removal efficiency were systematically elucidated, revealing a fundamental role of fine bubbles in lowering the sensitivity of the coagulation process to the solution potential environment. Specifically, the proposed process remarkably expanded the adaptive pH range of coagulation and weakened its dependence on zeta potential, thereby enabling efficient pollutant removal across a wider spectrum of aqueous conditions. Mechanistically, combined molecular dynamics simulations and experimental validations confirmed that the gas-liquid micro-interfaces of fine bubbles enriched target pollutants via non-bonded adsorption interactions. This interfacial enrichment mitigated steric hindrance during the coordination between PACl hydrolysis products and pollutants, significantly enhancing the efficiency of their complexation reactions. This distinct mechanism underpinned a heterogeneous coagulation pathway that departed from the traditional homogeneous bulk-phase paradigm. Driven by the synergistic effects of PACl forced hydrolysis and interfacial adsorption-facilitated complexation, the developed process achieved selective removal of micromolecular and hydrophilic organic matter in complex water matrices, while concurrently reducing the formation potential of disinfection by-products to a notable extent. This work provided critical theoretical insights into heterogeneous interface-driven coagulation chemistry and offered scalable technical guidance for the eco-efficient upgrading of traditional water purification processes, aligning closely with global sustainable development goals for safe and accessible drinking water.