OLIGODYNAMIC, COAGULATION ANDLIGAND- EXCHANGE CHEMISTRY VALIDATE INDIGENOUSINDIANWATER PURIFICATION PRACTICES: A FOCUSEDREVIEWSUPPORTING SDG-6
Rural and semi-urban India has relied for generations on indigenous, low-cost water purification practices that predate modern chemical engineering. This focused review narrows its scope specifically to the chemical mechanisms underlying such practices, excluding purely physical and biological explanations, to provide a focused, reaction-level account. Evidence was synthesised from eighteen peer-reviewed sources identified throughastructured literature search. Findings confirm that copper and silver vessel storage acts through oligodynamic metalion release and redox-driven oxidative damage to bacterial membranes; that seed-derived cationic proteins fromMoringa oleifera and Strychnos potatorum clarify turbid water through electrostatic charge neutralisationof colloidal particles; and that biochar and related carbonaceous materials remove fluoride through ligand-exchangereactions at hydroxylated metal-oxide surfaces. Surface and analytical chemistry techniques, including zeta potential analysis, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy and inductively coupled plasmamass spectrometry, corroborate these mechanisms at the molecular level. Thermodynamic parameters, includingGibbs free energy of adsorption, confirm the spontaneity of the underlying reactions. The reviewconcludes that indigenous Indian water purification practices rest on genuine, mechanistically explicable chemistry, and that thischemical evidence base offers a scientifically defensible foundation for the design of low-cost, culturally embeddedwater treatment systems. This mechanistic evidence base offers a scientifically defensible foundation for scalingthese practices into standardised, low-cost treatment protocols and directly supports Sustainable Development Goal 6 (Clean Water and Sanitation).
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