Mn2+ Removal From Water Using a Strong Acidic Shallow Shell Resin: Performance and Response Surface Optimization

Abstract

The removal of manganese ions (Mn2+) from aqueous solutions using a strong acid cation-exchange resin, Purolite SST60, was investigated in the present study. The influences of resin dosage, temperature, and pH on Mn2(+) removal were optimized using Response Surface Methodology based on a Central Composite Design. Results showed that removal efficiency was highly pH-dependent, increasing from 63% at pH 1.0 to over 99% at pH 3.0 and above. Even with only 0.01 g of resin, 98% removal was achieved, indicating high performance at low dosages. Equilibrium data aligned with the Langmuir isotherm, indicating monolayer sorption with a maximum capacity of 91.06 mg/g. Kinetic data followed a pseudo-second-order model. Thermodynamic analysis confirmed a spontaneous and exothermic process, supported by a negative enthalpy change and positive entropy change, likely due to dehydration of Mn2+ ions upon binding. Competitive ion studies revealed that divalent ions, particularly calcium and magnesium, significantly hinder Mn2+ removal, whereas monovalent ions had minimal impact. Complete desorption of Mn2+ was achieved using hydrochloric or nitric acid at concentrations of 0.5 mol/L and above, confirming the resin's reusability. Overall, Purolite SST60 offers an efficient, regenerable, and robust solution for manganese removal in water treatment applications.