Comprehensive review of modified clay minerals for phosphate management and future prospects

Phosphate recovery from water and wastewater serves as a feasible alternative to the exploitation of scarce phosphate rock resources. Currently, phosphate is recovered using adsorption-based techniques due to their desirable features, such as a low running cost, feasible operation, and high efficiency. Clay minerals (CMs), a group of earth-abundant resources, have attracted increasing interest in phosphate management. However, because the surface and crystal lattice of CMs are negatively charged, CMs are inefficient and have been replaced with cost-effective modified CMs (mCMs). This review comprehensively covers the current advances in mCM-mediated phosphate recovery. We first discussed the crystal features of natural CMs and the diverse techniques used for mCMs to enhance their phosphate-removal capacity. Subsequently, we covered the processes of mCM-driven phosphate management, namely, ion exchange, hydrogen bonding, crystallization, Lewis acid-base interactions, electrostatic interactions, precipitation, and electrostatic-ligand exchange. Further assessments revealed that mCMs can efficiently remove phosphate through multiple synergistic mechanisms. This review also discussed the effects of anions, humic acids, and cations on the mCMs management of phosphate and analyzed mCMs applications in various water environments, specifically, phosphate passivation materials in lake sediments and the phosphate management of municipal/seawater wastewater. We examined the reutilization of phosphate-loaded mCMs in agriculture from a circular economy perspective, and finally discussed the commercial application prospects of mCMs in environmental pollution remediation, which may help to avert the global phosphate-resource crisis and improve wastewater management.