Nano-geochemical interfaces for pollution mitigation: advancements in nanomaterial design, biogeochemical...

Environmental pollution driven by rapid industrialization, intensive agriculture, and urban expansion has resulted in widespread contamination of soil and water by heavy metals and organic pollutants, posing persistent ecological and human health risks. This study addresses a critical scientific gap by experimentally evaluating nano-geochemical interfaces as dynamic reaction zones that integrate nanomaterial surface chemistry with soil-water geochemical controls, rather than considering nanomaterials as isolated adsorbents. The work investigates the potential of engineered and green-synthesized nanomaterials to enhance pollutant immobilization and transformation through interactions with natural geochemical and biogeochemical processes. Metal and metal-oxide nanoparticles, including Fe-based oxides, TiO₂, and nanosilica, were synthesized on functionalized nanocomposite surfaces via chemical and green routes. The materials were comprehensively characterized using TEM, SEM, XRD, BET, FTIR, XPS, and zeta potential analyses. Batch remediation experiments were conducted in contaminated soil and aqueous systems containing heavy metals (Pb²⁺, Cd²⁺, As³⁺) and natural pollutants such as dyes and pesticide residues under varying pH and ionic strength conditions. Under optimized conditions, heavy metal removal efficiencies of 75-85% were achieved, with reductions in bioavailable soil metal fractions exceeding 80%, as confirmed by sequential extraction analysis. Adsorption behavior followed Langmuir and Freundlich isotherms, while kinetic data were best described by pseudo-second-order models, indicating chemisorption-dominated mechanisms. For organic pollutants, combined adsorption and photocatalytic processes resulted in 85-95% removal under UV and solar irradiation, with composite nanomaterials exhibiting enhanced charge separation and faster degradation rates. Reusability studies demonstrated high material stability, with less than 10% performance loss over five cycles and negligible metal leaching (< 1 mg L^-1). Overall, the results establish nano-geochemical interfaces as a robust, interface-centric framework for sustainable environmental remediation.