Acid functionalized polypropylene derivatives to adsorb Mn (II) from aqueous solutions: equilibrium, kinetics, and thermodynamic modeling

Polypropylene wastes were used to prepare carboxylated (CPP) and sulfonated (SPP) microparticles for the adsorption of Mn (II) from aqueous media. The microparticles derivatized with nitric or sulfuric acid were characterized in terms of their physico-chemical properties. The generated functional groups on CPP (-COOH and -NO2) and SPP (-COOH, -SO3H, and C = C) enhanced the adsorption of metal ions. The adsorption behavior of Mn (II) ions on the derivatized microparticles was studied under different conditions: Solution pH, polymer dose, contact time, initial concentration of Mn (II) ions, and temperature. Application of kinetics and equilibrium models to the data revealed that the adsorption processes followed pseudo-second order reactions and the Langmuir isotherm. SPP achieved a higher maximum adsorption capacity (9.15 mg g(-1)) than CPPs (5.51 mg g(-1)). Therefore, sulfonation was considered the most efficient approach to produce a suitable surface functionality for the removal of metal ions from aqueous solutions. However, thermodynamic studies showed that all adsorption processes are spontaneous and feasible (Delta G = - 1.32 and - 1.46 kJ mol(-1) at 20 degrees C for CPP and SPP, respectively), which ensure the possibility of employing acid-derivatized PP microparticles for metal removal.