Assessment of strongly acidic cation exchange resins for cadmium removal from wet phosphoric acid

The presence of cadmium (Cd) in wet phosphoric acid (WPA), a key intermediate in fertilizer production, poses a significant environmental and health risk due to the potential release of hazardous impurities throughout the fertilizer value chain. As global fertilizer demand intensifies, reducing Cd emissions has become a priority for sustainable production with regulatory compliance. This study evaluates the efficiency of sulfonic acid functionalized resins for the selective removal of Cd(II) ions from industrial WPA, aiming to support cleaner production practices and reduce the environmental footprint of the fertilizer industry. A series of batch experiments was conducted to assess the selectivity, capacity, and operational feasibility of selected cation exchangers under conditions representative of industrial operations. The adsorption process followed pseudo-second-order kinetics and the Langmuir isotherm model, with maximum monolayer capacities of 123.0 mg/g for K1131 S and 173.5 mg/g for K1461. Thermodynamic analysis confirmed that the process is spontaneous and endothermic, while surface characterization (SEM-EDX, XPS, FTIR-ATR) supported the proposed adsorption mechanisms. The results demonstrate that targeted Cd removal at the WPA purification stage significantly reduces the Cd load in downstream fertilizer products and minimizes the risk of soil and groundwater contamination. Overall, the findings indicate that ion exchange processes provide an effective strategy for improving WPA quality, thereby enabling the production of P-fertilizers that meet environmental and quality requirements.