Removal of Some Heavy Metals [Pb(II), Cd(II), Zn(II)] in Polluted Waters using Acid-Functionalized MCM-41 Mesoporous Materials: Adsorption Isotherm and Kinetic Studies

Abstract

Acid functionalized mesoporous silica materials like sulphonic acid (SO₃HMCM-41) and phosphotungstic acid (PWMCM-41) were synthesized by a simple co-precipitation method. These materials were characterized using XRD, SEM-EDS, FT-IR, BET surface area techniques. The mesoporosity was retained even after acid functionalization into MCM-41. There was a significant fall in the surface area (S_BET, m² g^-1), on incorporation of sulphonic acid (-SO₃H) and phosphorous, tungsten atoms into the MCM-41 material. SO₃HMCM-41 was found to be more acidic than PWMCM-41 and MCM-41. Their performance was evaluated by conducting experiments on the removal of heavy metals like Pb(II), Cd(II), Zn(II) present in industrial wastewaters, with atomic absorption spectrophotometer (AAS). The required experimental factors were analyzed and it was observed that the removal of metals was more efficient with the acid-functionalized materials than with MCM-41. Freundlich adsorption isotherm and pseudo-first order kinetics have confirmed the validity of the results.