Magnesium oxide loaded mesoporous silica: Synthesis, characterisation and use in removing lead and cadmium from water supplies

Abstract

Water pollution by potentially toxic elements such as cadmium (Cd) and lead (Pb) is a persistent problem in many parts of the world. It continues to have profound implications for drinking water supplies, wastewater discharge and environmental quality of rivers and lakes. Treatment is routinely needed but is not always accessible or practical for a given location or situation, hence new treatment options are the focus of much research. Nanotechnology has great potential to enhance water purification and decontamination efficiency. Nanomaterials have been shown to efficiently remove organic and inorganic pollutants, including metals, from contaminated waters but they can have a tendency to flocculate and thereby lose removal efficiency. Research aimed at stabilising nanoparticles into matrices such as silica offers a way forward. In this study, mesoporous silica (mSiO2, also referred to as MCM-41) was prepared and loaded with magnesium oxide nanoparticles (MgO-NP) to form a MgO-silica composite (MgO-mSiO2) and characterised using UV–Vis, FTIR, XRD, BET, and SEM techniques. The MgO-NP, mSiO2 and MgO-mSiO2 were then evaluated for their Cd and Pb removal capacity across varying conditions of pH, metal concentration, adsorbent: solution volume ratio and contact time. Sorption data were evaluated using the Freundlich, Langmuir and Temkin isotherm models. The MgO-mSiO2 was found to have a very high sorption capacity across the conditions tested, with >99% Cd removal across pH range 3–9 and >99% Pb removal across pH range 5–9. When tested at pH 6–7, the MgO-mSiO2 achieved nearly 100% adsorption efficiencies across the contact times tested (15–180 min).