Titanium(IV), Zirconium(IV), and Cerium(IV) Phosphates Synthesized Under Mild Conditions—Composition Characteristics and Evaluation of Sorption Properties Towards Copper Ions in Comparison to Commercially Available Ion-Exchange Resins

The removal of copper from wastewater of mine origin requires the use of an appropriate method. Sorption methods are considered to be one of the best solutions for removing copper from industrial wastewater at low levels. Metal(IV) phosphates have been reported as excellent sorption materials that can be highly selective for copper. Therefore, the aim of this research was to synthesize titanium(IV), zirconium(IV), and cerium(IV) phosphates with a wide range of P:Metal(IV) molar ratios (0.5-10) in the reaction mixture and under mild conditions, using a simple scalable approach which requires minimal financial outlays. The obtained materials were characterized using XRD, ATR-FTIR, SEM-EDS techniques, and pH titration. To evaluate the performance of the resulting materials, their sorption properties towards copper ions were examined in comparison with selected commercially available ion-exchange resins. In each group of metal(IV) phosphates, the best material has a high ion-exchange capacity: 16.9 meq/g for titanium sorbent, 8.8 meq/g for zirconium sorbent, and 7.0 meq/g for cerium sorbent. Zirconium phosphate synthesized at a P:Zr molar ratio in the reaction mixture of 10:1 exhibits the best sorption properties towards copper ions in a solution similar to mining wastewater (acidic, saline, and containing heavy metals), better than some commercial ion-exchange resins.