Removal of heavy metals using activated carbon from microwave steam activation of palm kernel shell

Abstract

The presence of toxic heavy metals contributes towards the deterioration in the quality of water resources. In this work, microwave steam activation (MSA) was conducted to convert palm kernel shell into activated carbon (PKSAC). MSA provided a rapid heating rate (up to 140 °C/min) at 700 °C under a steam flow rate of 5 g/min for 45 min. PKSAC was obtained, showing high BET surface area (539.75 m2/g) with low H/C and O/C ratios, indicating a high degree of carbonization and stability of PKSAC to act as a durable adsorbent. The PKSAC was then applied to remove heavy metals (i.e. Cd2+ and Pb2+) present in landfill leachate (LL). Batch experiments were performed to investigate the effects of initial ion concentrations and contact times on Cd2+ and Pb2+ adsorption under optimal condition. Maximum Cd2+ and Pb2+ removal of 116.0 mg/g and 59.9 mg/g, respectively were obtained at pH 3, initial concentration of 100 mg/L, and adsorbent dose of 0.2 g. Results showed that the adsorption kinetics of Cd2+ and Pb2+ can be described by the pseudo second order kinetics model, while Freundlich isotherm was well fitted to the Cd2+ and Pb2+ adsorption data. Overall, the PKSAC produced by MSA is a promising and cost-effective adsorbent for removal of Cd2+ and Pb2+.

Keywords

• Microwave pyrolysis
• Activated carbon
• Steam activation
• Oil palm biomass
• Leachate