<p>Chromium residue is a highly toxic and strongly oxidizing hazardous waste from chromium salt production. Its resource utilization is crucial for environmental protection and sustainable development. This study addresses the key challenges in conventional chromium residue treatment, particularly the low-resource utilization efficiency and the adverse effects of P and Ca impurities on chromium recovery and product purity. A novel process combining alkaline roasting with gradient removal of P and Ca impurities was developed. Under optimal roasting conditions (chromium residue to Na₂CO₃ mass ratio of 1:1.5, roasting temperature of 800&#xa0;℃, oxygen flow rate of 80&#xa0;mL/min, and roasting time of 120&#xa0;min), a chromium leaching rate of 86% was achieved. A gradient separation strategy was then implemented: the aqueous solution of the roasted clinker was first neutralized to remove CO₃²⁻, followed by MgCl₂ addition under strongly alkaline conditions (pH: 12.0–14.0) for deep P and Ca removal. The study revealed that Mg²⁺ plays a dominant role in precipitating PO₄³⁻, while Mg(OH)₂ facilitates Ca²⁺ removal through a synergistic adsorption-co-precipitation mechanism. The addition of 3.0&#xa0;g of MgCl₂ achieved high removal efficiencies of 99.56% for P and 98.31% for Ca, with corresponding residual contents in the Na₂CrO₄ solution reduced to 0.45&#xa0;mg/L and 1.12&#xa0;mg/L, respectively. This process provides a reliable theoretical foundation and an effective technical approach for the efficient recovery of chromium and deep purification of P and Ca impurities from chromium residue.</p> Graphical Abstract <p></p>