Municipal solid waste-derived biochar for the removal of benzene from landfill leachate

The potential of biochar, produced from fibrous organic fractions of municipal solid waste (MSW), for remediation of benzene, one of the frequently found toxic volatile organic compounds in landfill leachate, was investigated in this study based on various environmental conditions such as varying pH, benzene concentration, temperature and time. At the same time, landfill leachate quality parameters were assessed at two different dump sites in Sri Lanka: Gohagoda and Kurunegala. MSW biochar (MSW-BC) was produced by slow temperature pyrolysis at 450 °C, and the physiochemical characteristics of the MSW-BC were characterized. All the leachate samples from the MSW dump sites exceeded the World Health Organization permissible level for benzene (5 µg/L) in water. Removal of benzene was increased with increasing pH, with the highest removal observed at ~pH 9. The maximum adsorption capacity of 576 µg/g was reported at room temperature (~25 °C). Both Freundlich and Langmuir models fitted best with the equilibrium isotherm data, suggesting the involvement of both physisorption and chemisorption mechanisms. Thermodynamic data indicated the feasibility of benzene adsorption and its high favorability at higher temperatures. The values of Δ G suggested physical interactions between sorbate and sorbent, whereas kinetic data implied a significant contribution of chemisorption. Results obtained from FTIR provided clear evidence of the involvement of functional groups in biochar for benzene adsorption. This study suggests that MSW biochar could be a possible remedy for benzene removal from landfill leachate and at the same time MSW can be a potential source to produce biochar which acts as a prospective material to remediate its pollutants while reducing the volume of waste.