Enhanced adsorption capacity and selectivity towards strontium ions in aqueous systems by sulfonation of CO2 derived porous carbon

Abstract

Oxygen-enriched carbon materials derived from carbon dioxide were functionalized using sulfonic acid to remove Sr²⁺ ions from aqueous solutions. Synthesized sulfonated porous carbon materials (PC-SO₃H) showed higher adsorption capacity and selectivity towards Sr²⁺ than non-functionalized porous carbons (PC). The formation of the C-SO₃H functional group in PC-SO₃H and its ability to proton exchange with Sr²⁺ was the main contributor to the enhanced performance. The maximum uptake capacity of Sr²⁺ by PC-SO₃H was 18.97 mg g⁻¹, which was 1.74 times greater than PC. PC-SO₃H removed 99.9% and 97.6% of Sr²⁺ from aqueous solutions with initial Sr²⁺ concentrations of 5 mg L⁻¹ and 10 mg L⁻¹, respectively. Sr²⁺ adsorption showed rapid kinetics, reaching the adsorption equilibrium within 1 h with high adsorption capacity at equilibrium which is 3.52 times greater than that of PC. Additionally, PC-SO₃H selectively adsorbed Sr²⁺ even in the presence of excess amounts of competing ions. Sulfonation of oxygen-enriched carbon had a significant effect on enhancing the affinity towards Sr²⁺ and suppressing adsorption towards other competing ions.