Preparation of high-efficient KMnO4 modified biochar for heavy metal removal from municipal wastewater

KMnO4-modified biochar (KM/biochar) derived from cotton stem is prepared with different cotton stem/KMnO4 ratios for Pb(II) removal from wastewater. The characterization analysis indicates that KM/biochar has abundant surface functional groups and large surface area, contributing to Pb(II) removal. Pb(II) adsorption on KM/biochar can be accurately analyzed using the Pseudo-second order and Hill model. The maximum Pb(II) adsorption capacity of KM/biochar is 144.49 mg/g at pH of 5. Pb(II) adsorption on KM/biochar is spontaneous based on thermodynamics analysis with the enthalpy value of the 8.54 kJ/mol. Coexisted ions such as Na+, K+, Ca2+ and Mg2+ have slightly influenced on Pb(II) adsorption process. The regeneration experiment analysis indicates that KM/biochar shows excellent Pb(II) adsorption capacity after three cycles. The existence of CO2 can contribute to Pb(II) removal from wastewater. Pb(II) adsorption mechanism includes precipitation, cation exchange, electrostatic attraction and π-π interaction. These above analysis results indicate that the waste cotton stem can be converted into the high-efficient KM/biochar for Pb(II) removal from wastewater.