Application of rice and corn husk biochar for removal of heavy metal ions from industrial wastewater

Abstract

This study investigated the removal of heavy metal ions from industrial wastewater by using rice and corn husk biochar. The choice of the materials was influenced by their largest surface area, plentiful functional groups and their availability in the local environment. Rice and corn husks were pyrolysed at 500, 600, and 700 °C to make biochars that were used to treat low quality industrial wastewater. Carbonisation of rice husks at 600 °C produced the best removal efficiencies for Cr (65%), Fe (90%) and Pb (> 90%). The carbonisation of corn husks at 600 °C produced the worst removal efficiencies for Cr (only 20%) and Pb (slightly > 35%). Regardless of the carbonisation temperature, rice husk biochars performed better than corn husk biochars. All data fitted well in both the Langmuir and Freundlich isotherm models (R 2 values ranging between 0.82 and 0.99). The Langmuir separation factor RL was had negative values; probably due to the low initial concentration of the adsorbates in the raw wastewater. All the biochars showed a relatively short contact time (20 to 30 min) to attain maximum adsorption efficiencies – a promising feature for future industrial applications. The studied biochar materials from rice and corn husk have the potential to remove heavy metal ions from industrial wastewater; rice husk biochar showed higher removal capacity than corn husk.