Characterisation of activated carbons for removal of organic and heavy metal pollutants from water in resource limited countries
George Kalaba, James Nyirenda, Onesmus Munyati
Abstract
ABSTRACT Water contamination by heavy metals and organic waste presents a great challenge in developing countries, thereby hampering access to safe water. In this work, activated carbons were prepared from Zea mays cob (MC), Anacardium occidentale (cashew nut shells – CNS), sawdust from Pinus oocarpa (SPO) and Pterocarpus angolensis (SPA) biomass waste found in Zambia. The activated carbons were used as filters to remove heavy metals and organic pollutants from aqueous solution. The average adsorption efficiency of heavy metals was 99.10 ± 0.6%, 99.38 ± 0.4%, 98.43 ± 0.6% and 99.40 ± 0.4% for SPA, SPO, CNS and MC, respectively. Adsorption was found to follow Langmuir model for CNS and Freundlich model for SPA, SPO and MC. The adsorbent with high adsorption efficiency of heavy metals, MC was characterized using Fourier-transform infrared spectroscopy and further tested for methylene blue (MB) removal by adsorption. The kinetic data for adsorption of MB were best fitted by the pseudo-second-order kinetic model. The highest percentage removal of MB at equilibrium was 99.69 ± 0.3% at 50 mg/L and the lowest was 96.47 ± 0.1% at 350 mg/L indicating that maize cob activated carbon is an excellent adsorbent in the removal methylene blue and heavy metals even at low concentrations.