Modelling of manganese-contaminated groundwater through batch experiments: Implications for bone char remediation

Abstract

In this study, bone char was successfully produced by the thermal pyrolysis of cattle bones at 450 °C using a locally designed double barrel retort drum. The bone char was characterised by the point of zero charge, scanning electron microscopy/energy dispersive x-ray, Fourier-transform infrared, and Brunauer-Emmett-Teller analysis. Manganese (II) contaminated groundwater and laboratory-prepared aqueous manganese solutions were treated with the prepared bone char. Modelling of the manganese (II) remediation of the natural groundwater by cattle bone char was investigated for its application to water quality. Adsorption kinetics and investigations of the Freundlich and Langmuir model isotherms were part of the batch adsorption experiments that were utilised to evaluate the removal capabilities of the char under different metal concentrations, contact time, pH, and char dose. The thermodynamic variables showed that manganese (II) ions adsorption by the cattle bone char was an exothermic and spontaneous process. Regarding regression coefficients, the Freundlich isotherm model outperformed the Langmuir model in predicting the best match or fit for the adsorption data. The maximum removal rate of manganese (II) ions by the bone char in 60 min was estimated to be 99.2% under laboratory-controlled conditions. An amount of 0.515 mg/L of manganese (out of 0.645 mg/L) from natural groundwater was adsorbed on 1 g of 0.315 mm bone char, whereas 0.05 mm of the bone char adsorbed 0.639 mg/L manganese (II) ions. The use of bone char from cattle bones is an effective and sustainable solution for the treatment of manganese contamination of groundwater. The char of cattle bone can be utilised as a safe and environmentally acceptable adsorbent.