Nonferrous Metals(Extractive Metallurgy)

During the copper electrolytic refining process, antimony(Sb) and bismuth(Bi) in the electrolyte are prone to hydrolysis to form floating anode slime, which adsorbs onto the cathode surface to form physical inclusions, reducing the purity and surface quality of the cathode copper. Traditional removal methods have shortcomings such as high energy consumption, secondary pollution or complex operation, while ion exchange methods demonstrate industrial potential with advantages such as simplicity, free secondary pollution and renewability. This study determines the adsorption behavior and rate-controlling mechanisms of Sb and Bi removal from high-acidity copper electrolyte by Lewatit® MonoPlus TP260 aminomethylphosphonic acid chelating resin under conditions simulating industrial electrolyte with fluctuating impurity levels. Static batch adsorption experiments were performed with synthetic copper electrolyte containing 45 g/L Cu, 150 g/L H₂ SO₄, and Sb and Bi concentrations of 0.03–0.15 g/L. The TP260 resin(aminomethylphosphonic acid functional groups on macroporous styrene-divinylbenzene matrix, exchange capacity 2.4 mmol/g) was preconditioned by successive 4% HCl and 4% NaOH(mass concentration) treatments. Adsorption tests varied resin dosage(20–100 g/L), temperature(20–70 ℃), and contact time(1–180 min). Residual Sb, Bi, and Cu concentrations were measured by ICP-OES. Removal efficiency was calculated as η=(C_o-C_e)/C_o×100%. Equilibrium data at initial concentrations of 30–150 mg/L were fitted to Langmuir and Freundlich models. Kinetic data were fitted to the pseudo-second-order model and analyzed by the Weber-Morris intra-particle diffusion model. Regeneration was conducted in a glass column with 4.0 mol/L HCl at 60 ℃ and 2 BV/h; six adsorption-regeneration cycles were completed under optimum conditions. The results show that under the optimum static adsorption conditions(60 g resin/L, 60 ℃, 60 min), Sb removal rate is 96.25% and Bi removal rate is 98.00%, while Cu adsorption is negligible. Removal efficiency increases rapidly with resin dosage up to 60 g/L and then leveled off. Temperature has only a minor effect on Sb removal(96.25%–97.19%) and a slight positive effect on Bi removal. Equilibrium isotherms conform to the Freundlich model(R²=0.9460 for Sb and 0.9393 for Bi). The pseudo-second-order model fits the kinetic data with R²>0.999; calculated equilibrium capacities(1.21 mg/g for Sb and 1.22 mg/g for Bi) deviates by less than 1 % from experimental values. Weber-Morris plots show three linear stages. The intra-particle diffusion rate constants for Sb are 0.083 93 mg/(g · min^0.5)(0–5 min), 0.009 12 mg/(g · min^0.5)(10–30 min), and 0.001 93 mg/(g · min^0.5)(40–180 min), respectively. Corresponding values for Bi are 0.098 95, 0.011 72, and 0.002 11 mg/(g · min^0.5), respectively. Dynamic elution with 4.0 mol/L HCl achieves 94.22% Sb and 96.83% Bi desorption within 5 bed volumes. After six cycles, Sb removal rate remains 93.46% and Bi removal rate remains 95.72%; desorption efficiencies stay above 92%. Adsorption of Sb and Bi onto TP260 resin follows multilayer heterogeneous coverage described by the Freundlich isotherm. The process is controlled primarily by chemisorption between aminomethylphosphonic acid groups and SbO⁺/BiO⁺ species. WeberMorris analysis confirms a multi-step mechanism in which liquid-film diffusion and surface chelation dominates the initial 0–5 min, intra-particle diffusion governs the 10–30 min interval, and equilibrium is approached after 60 min. The resin shows stable regenerability, retaining more than 97% of initial capacity after six cycles. These kinetic and regeneration parameters provide a quantitative basis for fixed-bed purification systems that integrate with existing copper electrorefining circuits. The three-stage Weber-Morris diffusion behavior supplies explicit rate constants and boundary-layer contributions for this resin in copper electrolyte matrices. The cycle stability data under identical conditions supplies practical lifetime estimates and acid consumption figures for process costing.