Effects of biochar derived from potato straw on adsorption of Cd(Ⅱ) onto loess
In order to investigate the feasibility of adsorption-immobilization remediation for heavy metal-contaminated loess soils using biochars originated from the local agricultural wastes,the adsorption of Cd(Ⅱ) onto the biochar derived from potato straw,loess and loess with the biochar was investigated.The biochar and loess before and after adsorption were characterized by X-ray diffraction (XRD) and FTIR spectra.The influences of contact time,pH value of solution and initial Cd(Ⅱ) concentration on the adsorption were studied by batch adsorption experiment.The results indicated that the adsorption isotherms for all three adsorbents were well fitted with Langmuir model and the maximum adsorption capacities were 15.60,7.87,12.40 mg·g-1 at 25 ℃,respectively.The adsorption kinetics were well described by pseudo-second kinetic model.The solution pH exhibited a significant impact on adsorption.The adsorption capacity increased rapidly when the pH increased from 2 to 4 and from 6 to 8.When the pH values increosed from 4 to 6,the adsorption capacity increased gradually.The characterization results indicated that ion exchange and cation-π interaction were the main adsorption mechanisms of Cd(Ⅱ) onto biochar.The adsorption of Cd(Ⅱ) onto loess could be attributed to the clay minerals including quartz,kaolinite and the carboxyl groups in organic matter.According to the data from kinetics and isotherms,the adsorption capacity of Cd(Ⅱ) onto loess increased by 41.50％ and 49.94％ respectively when the loess was mixed with biochar within the experimental study,which showed that the amendment of biochar could effectively improve the adsorption capacity of loess to Cd(lⅡ) under above conditions.
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