Spinel ferrite magnetic adsorbents: Alternative future materials for water purification?

Spinel ferrite (SF) magnetic materials are an important class of composite metal oxides containing ferric ions and having the general structural formula M²⁺Fe₂³⁺O₄ (where M = Mg²⁺, Co²⁺, Ni²⁺, Zn²⁺, Fe²⁺, Mn²⁺, etc.). SFs possess unique physicochemical properties including excellent magnetic characteristics, high specific surface area, surface active sites, high chemical stability, tunable shape and size, and the ease with which they can be modified or functionalized. As a result of their multifunctional properties, affordability, and magnetic separation capability, SF adsorbents are a top choice for water purification applications that require high adsorption efficiencies and rapid kinetics. In this review, we discuss adsorption performance and possible applications of SFs and their derivatives for treating a wide range of aqueous pollutants such as metal ions, dyes, and pharmaceuticals. Key parameters influencing the sorption performance such as particle size, shape, annealing temperature, functionalization, and metal ion doping have been comprehensively discussed. In addition, adsorbate-adsorbent interactions, desorption, regeneration, and utilization of spent adsorbent have also been summarized. The review also covered, how SFs are prepared from industrial waste using green synthetic routes and general remarks about toxicological effects.