Author(s)

T. Falayi, F. Ntuli, Z. B. Sithole

Abstract

Potassium silicate solutions obtained were used as a source for MCM41. The preparation of MCM41 was affected by the gelation pH. A pH of 7 produced the purest MCM41 with an external surface area of 98,000 m² m⁻³. The MCM41 could be used as an adsorbent for heavy metals in AMD. A 4% m/v solid loading of MCM41 could remove 95.5, 97.3 and 99.6% of Ni, Cu and Fe respectively. The adsorption process was found to fit the Langmuir isotherm and pseudo second order kinetics. The Gibbs free energy of adsorption for all metals was below -20 kJ/mol for all metals. The enthalpy for Fe, Cu and Ni removal were 19.97, 21.40 and 16.44 kJ/mol respectively and thus endothermic. The entropy for the removal of Fe, Cu and Ni were found to75.6, 76.2 and 56.5 J/mol respectively showing the strong affinity of MCM41 for the metals. The process was also thermodynamically spontaneous with the spontaneity increasing with an increase in temperature.

Keywords

MCM41, adsorption, heavy metals, isotherm