Investigation of membrane scaling and fouling in nanofiltration treatment of landfill leachate based on quantum chemical Parameters

Nanofiltration (NF) technology has been widely applied for the efficient removal of organic pollutants from water. However, frequent membrane fouling and scaling remain significant challenges in practical applications. To better understand the mechanisms and patterns underlying NF membrane scaling and fouling, this study first employed X-ray diffraction (XRD) and inductively coupled plasma optical emission spectrometry (ICP-OES) to identify calcium (Ca2+) and ferric ions (Fe3+) as the dominant cations contributing to scaling. Subsequently, simulated wastewater experiments were conducted to develop quantitative structure-activity relationship (QSAR) models for organic pollutant adsorption in CaCl2 and FeCl3 systems using stepwise regression method. The optimal QSAR models were determined as Re%=1.938×10−5EB3LYP−0.514q(H)−0.023ELUMO + 0.269 and Re%=−0.0003EB3LYP+1.055q(C)n−0.074EHOMO−0.278, respectively. Validation results demon-strated the stability and predictive accuracy of these models for estimating the adsorption efficiency of organics. Quantum chemical parameter analysis revealed that molecular energy/size, partial charges on carbon and hydrogen atoms, and frontier orbital energies were key intrinsic quantum factors influencing the removal of organic pollutants in the CaCl2 and FeCl3 systems. Mass spectrometry analysis, combined with quantum chemical calculations and the QSAR models, further uncovered that the primary cause of membrane fouling and subsequent scaling in real landfill leachate was the interaction between organics and Ca2+. This study provides a quantum chemical perspective on the mechanisms and patterns of NF membrane fouling and scaling and offers a foundation for evaluating organic pollutant removal behavior in fouled NF membranes.