Removal of Mn2+ from Polluted Groundwater Using a Natural Ghanaian Brown coal: Batch experiments and geochemical modelling

Abstract The study investigated the efficacy of natural Ghanaian brown coal (BC) in treating water contaminated with harmful levels of manganese (Mn2+). Batch adsorption experiments were performed to assess various factors, including Mn2+ concentration, BC dosage, temperature, and pH, to determine optimal conditions for Mn2+ removal. The thermodynamic and equilibrium studies indicated that the adsorption was spontaneous, favourable and endothermic. The highest adsorption occurred at pH 6. The adsorption kinetics was accurately described by the pseudo-second-order kinetic model, while the Langmuir isotherm excellently fit the experimental data, with a maximum adsorption capacity of 1.19 mg/g. The BC proved to be environmentally friendly and recyclable. Adsorption efficiency remained high (>80%) after 4 cycles of adsorption/desorption. However, the presence of competing cations (e.g., Cu2+) could impact its effectiveness. The adsorption mechanisms involved ion exchange with Ca2+, Mn2+, Na+, K+, and complexation with surface functional groups. The study in general suggests that the Ghanaian BC possesses favourable environmental characteristics and holds promise for Mn2+ removal in industrial applications.