The Study On Adsorption Of Heavy Metal Lead On Biochars Derived From Corn Straw

At present,the comprehensive utilization of agricultural wastes such as straw and the treatment of heavy metal wastewater are hot issues of the environment.The biochar is prepared by pyrolyzing corn straw from Fuxin under a limited oxygen condition and the impregnation method is used to prepare the magnetic biochar.They are used to study the adsorption characteristics of heavy metal lead.And it can provide a theoretical basis for the treatment of wastewater containing lead.First,the biochars are characterized qualitatively and quantitatively,including BET to determine the specific surface area,SEM to study the surface microscopic structure,infrared spectrum to study the chemical structure and so on.The kinetics and isothermal adsorption characteristics of lead are obtained by the batch experiment under different environmental factors.The results of the adsorption kinetics of lead on the biochar showed that the adsorption process was consistent,which was divided into rapid and slow adsorption stage.And the reaction approached equilibrium at about 30h.Quasi-two dynamics equation could describe the adsorption process of lead on the biochar well.It showed that the adsorption process dominated by chemical adsorption.The activation energy required for intraparticle diffusion of the adsorption(13.6 KJ/mol)was larger than the membrane diffusion(11.8 KJ/mol)through the calculation of activation energy.It indicated that the intraparticle diffusion was the main control step of the adsorption process.The result of the two-compartment model analysis was that Ffast were greater than 0.5 at different influence factors.It showed that fast adsorption was dominant.The results of the isothermal adsorption of lead on biochar indicated that the biochar had a strong adsorption capacity.And its adsorption process could be described by Langmuir and Freundlich model.With the increase of temperature,pH and the decrease of ionic strength,the adsorption quantities of lead on the biochar increased.The results of the adsorption of lead on the magnetic biochar showed that the adsorption quantity of lead on the magnetic biochar was significantly greater than that on the biochar at the same temperature.It indicated that the magnetic biochar had a stronger adsorption capacity on lead.With the increase of temperature,the adsorption capacity increased first and then decreased.The analysis of isothermal adsorption showed that the adsorption process conformed to the Langmuir model and the Langmuir Adsorption-Partition model.With the increase of temperature,the calculated distribution coefficient Kd and the contribution ratio of the distribution by the composite model decreased gradually.Therefore,the adsorption of lead on the magnetic biochar was dominated by physical adsorption firstly.With the increase of temperature,the adsorption process was dominated by chemical adsorption...