Removal of Pb2+ and Cd2+ from aqueous solution using chars from pyrolysis and microwave-assisted hydrothermal carbonization of Prosopis africana shell

Biochar and hydrochar prepared from pyrolysis and microwave-assisted hydrothermal carbonization of Prosopis africana shell respectively were used as adsorbents for the removal Pb2+ and Cd2+ from aqueous solution using batch adsorption technique. The materials proved to have good adsorption capacities and higher than some previously studied adsorbents. Maximum adsorption capacities for the hydrochar and biochar were 45.3 and 31.3 mg/g for Pb2+ and 38.3 and 29.9 mg/g for Cd2+, respectively. The adsorption process followed pseudo-second-order kinetics and the adsorption data fitted the Langmuir isotherm model. These materials could therefore be used as a low cost adsorbents in wastewater treatment.