Boosting the phosphate adsorption of calcite by low Mg²⁺-Doping

Calcite is a promising material choice for adsorbing phosphates because of its abundance and environmentally benign nature. However, the slow adsorption kinetics and hence low adsorption capacity within a short time frame hinders its practical application. In this work, we solve these problems by presenting a low Mg²⁺-doped calcite adsorbent, Mg-10. With a 3.75 wt% of Mg²⁺ doping, Mg-10 exhibits a remarkable adsorption capacity of 157.7 mg P/g. It also demonstrates a substantial boost in the adsorption kinetics, achieving a sixfold increase in adsorption capacity within 24 h compared to the undoped calcite. Meanwhile, Mg-10 not only offers improved adsorption selectivity but also maintains a stable effluent pH, underscoring its environmental compatibility. By conducting soil column experiments, we find that Mg-10 quickly captures the excess phosphates during the mimicking fertilization process, and slowly releases the nutrient afterwards, which can increase the feralization efficiency. These results provide alternative strategies for managing phosphate pollution originated from fertilization, and underscores the potential of Mg-10 in sustainable agriculture and environmental remediation.