A review of phosphate adsorption on Mg-containing materials: kinetics, equilibrium, and mechanistic insights

Abstract

Significant efforts have been made to remove excess nutrient phosphorus in the form of aqueous phosphate ions from various wastewater streams to mitigate adverse environmental consequences to the watershed, such as eutrophication. Adsorption has long been a low-cost and highly effective method of phosphate removal which chiefly relied on immobilizing this valuable nutrient in low solubility solids. Magnesium-based adsorbents are emerging as an economically feasible solution to the phosphate removal problem that have the added benefit of facilitating nutrient recycling via the production of slow-release fertilizer. The current scientific literature on Mg-based adsorbents for phosphate has focused on a diverse range of techniques for the resulting material characterization, adsorption equilibrium and the observed kinetics making direct comparison between the diverse Mg-based adsorbents difficult. This tutorial review aims (a) to provide an overview of the state of the art in Mg-based phosphate adsorbents and (b) to propose a generalized data interpretation roadmap necessary to bridge the gap between the observed fundamental kinetics and mechanistic insights reported in the literature.