Physicochemical characterization of biochars from Eucalyptus maiden Entandrophragma cylindricum (Liboyo), Milicia excelsa (Muvula.) and Ocotea michelsonie (licheche) used in Goma city, DR Congo for water treatment potentials

Abstract

In recent years, research on biochar as an eco-friendly material and cost-effective means for water treatment, soil amendment and carbon sequestration has gained more attention due to the availability of feedstock, the simplicity of the preparation methods, and their enhanced physico-chemical properties. Given that pyrolysis temperature and resident time amongst other factors have significant effect on biochar’s pollutant removal efficacy, this study focused on the evaluation of some properties of biochars produced by pyrolysis (500 - 600 °C) from Entandrophragma cylindricum (ECB), Eucalyptus maiden (EMB), Milicia excelsa (MEB) and Ocotea michelsonie (OMB) sawdusts for their water treatment potentials by using standardized methods. Biomass generated from wood mill in the city of Goma (DR Congo) is valorised for the first time as potential water  purifier. The highest yield was obtained from OMB (36.6%) which was found to be significantly greater that those of ECB and EMB (p<0.05). All the biochars had neutral to weakly alkaline pH (7.10-7.90), very high porosity (92-94%, with EMB having the highest value) and ash content between 9.40 and 18.40%, with the highest value attributed to OMB). Most physical and chemical characteristics of biochars varied significantly due to different wood species. Potential toxic elements were far below
environmental threshold values and exchangeable cations were equally detected in the biochars. The obtained biochars are therefore seen as good media for water treatment.