Adsorption characteristics and mechanisms of fallen leaves biochar towards Cd(Ⅱ)in water
Given the problems of heavy metal pollution in water and the difficulty in effectively utilizing the fallen leaves,biochars were prepared with fallen leaves of Platanus orientalis L.and Salix babylonica L.in this study.The microstructure and composition of biochars were analyzed by BET,SEM and FTIR.Their adsorption characteristics and influence factors to Cd2+were studied through adsorption experiments.The results showed that the removal rate of Cd2+was positively correlated with solution pH and biochar dosage,and negatively correlated with electrolyte CaCl2 concentration.The adsorption processes of both types of biochar conformed to the Elovich equation and the quasi second-order kinetic equation and were dominated by heterogeneous chemisorption.The adsorption processes of the Platanus orientalis L.fallen leaves biochar(BCP)and Salix babylonica L.fallen leaves biochar(BCS)followed Langmuir and Freundlich adsorption isotherms,with maximum adsorption amounts of 5.57 mg·g-1 and 10.18 mg·g-1,respectively.According to the orthogonal experiments,the optimal adsorption conditions for BCP and BCS were as follows:the concentration of CaCl2 solution was 0.05 mol·L-1,pH=7,BCP dosage was 0.05 g,and the pyrolysis temperature was 500 ℃;the concentration of CaCl2 solution was 0 mol·L-1,pH=7,BCS dosage was 0.05 g,and the pyrolysis temperature was 400 ℃.This study provides a reference method and important scientific basis for the removal of Cd(Ⅱ)in water and the effective utilization of fallen leaves.
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