Innovative strategy of turning waste into treasure: High-efficiency adsorption of heavy metals pollutants by modified amorphous calcium phosphate prepared with phosphogypsum waste

Abstract

In the present work, phosphogypsum (PG) waste was used as a calcium source, and integrated with 2-hydroxyphosphonoacetic acid (HPA) doping, modified inorganic-organic amorphous calcium phosphate hybrid composite was prepared, to remove Cd2+ and Co2+in aqueous solution. The study demonstrated that when pH=8, the equilibrium adsorption capacity of hydroxyapatite (HAP) for Cd2+ and Co2+ can reach 275.84 mg/g and 70.63 mg/g, respectively. After modification with HPA, the adsorption capacity of 20HPA-HAP for Cd2+ and Co2+ was higher at 468.92 mg/g and 171.38 mg/g, respectively. Regeneration experiments show that the adsorbent has good recycling performance, and the adsorbent has a good adsorption effect on low-concentration cadmium and cobalt ions in the actual hard gold electroplating wastewater. Meanwhile, the adsorption mechanism of 20HPA-HAP for Cd2+ and Co2+ was vividly visualized through Multiwfn wavefunction program and VMD program. Therefore, the reason why doping HPA greatly improves the adsorption performance of amorphous calcium phosphate on heavy metal ions was revealed from the atomic point of view. The findings suggest a promising approach for the effective utilization of discarded PG and the effective treatment of heavy metal pollution in industrial wastewater, highlighting the dual benefit of waste material repurposing and pollution control, which was an innovative strategy of turning waste into treasure.