High-efficiency adsorption of heavy metal ions by Na2S modified biochar:preparation and adsorption mechanism
In this study,Na2S modified biochar(BCS)with efficient adsorption properties for Pb2+,Cd2+,and Zn2+was prepared by using waste reed as raw material and sodium sulfide(Na2S)as modifier.The biochar before and after modification was characterized by scanning electron microscopy-EDS(SEM-EDS),infrared spectroscopy(FTIR)and elemental analysis.The results showed that the Na2S modification was able to introduce various sulfur-containing functional groups into the biochar,enhance the pore volume and increase the specific surface area.The Langmuir model fitting results indicated that the adsorption capacity of BCS for heavy metal ions was enhanced with the increase of the concentration of the modifier Na2S solution.In the pH range of 2.0-6.0,the adsorption capacity of BCS on heavy metal ions was gradually enhanced with the increase of pH.At pH=6.0,the maximum adsorption amounts of BCS on Pb2+,Cd2+and Zn2+were 494.99,131.14 and 94.89 mg/g,respectively.Based on the results of the kinetic experiments,it can be seen that the adsorption behaviors of BCS on heavy metal ions were in accordance with the pseudo-secondary kinetic model.The adsorption mechanism mainly includes complexation of surface functional groups,ion exchange and electrostatic adsorption.Overall,this study provides an environmentally friendly and feasible solution for the reuse of waste and the efficient removal of heavy metals from wastewater.
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