Adsorption Of Ammonium By Modified Peanut Shell Biochar In Groundwater Polluted By Electrolytic Manganese Slag

With the development of electrolytic manganese metal(EMM)industry in China,slag produced by EMM industry bring a great threat to the environment.The slag was mostly buried in the open landfill.The rainfall might cause the pollutants infiltrate into the soil and enter the groundwater and ammonium was one of the important pollutants.Therefore,it is significant to control the conconcentration of ammonium in the groundwater polluted by the slag.It was difficulty of microorganism growth due to manganeses in the groundwater polluted,biological treatment method could not be used,and the electrochemical oxidation method is expensive,so In this study,adsorption was used to remove ammonium with low cost and easy to operate.Compared with the adsorptive performance of biochars for ammonium studied by predecessors of the research group,the modified peanut shell biochar with the best effect was selected.The adsorption efficiency of modified peanut shell biochar on ammonium was explored.The removal conditions of ammonium in the groundwater contaminated by the slag were analyzed,and the adsorption mechanism was analyzed.Moreover,the performance of modified peanut shell biochar in dynamic adsorption was investigated,and predicted the parameters by model simulation.The main results were as follows:①It was found that the adsorptive capacity of this biochar increased first and then decreased with the increase of dosage,pH,initial ammonium concentration,and adsorption time.When Mn(Ⅱ)was introduced into the solution,the adsorptive capacity of NH4+-N was slightly affected.②It was found that the Langmuir-Freundlich model could better describe the process of removing ammonium by peanut shell biochar before and after modification,and the maximized adsorptive capacity for ammonium was 3.82 mg/g and 6.92 mg/g respectively.The fitting effect of the quasi second-order kinetic equation to the modified peanut shell biochar was the best,which indicated that the main adsorption of ammonia nitrogen was chemical adsorption.③Through SEM-EDS,FTIR and XPS,combined with previous studies,the adsorption mechanism of modified peanut shell biochar for ammonium was obtained,which includes four aspects:first,electrostatic effect;second,ion exchange effect;third,surface complexation;fourth,cation π-bond effect.④In the dynamic adsorption experiment,it is found that the penetration and saturation time could be prolonged by reducing the amount of biochar filled in the fixed bed and the initial concentration and flow rate of the influent.Thomas model,Adams Bohart model and Yoon Nelson model could be used to describe the dynamic adsorption of ammonium on modified peanut shell carbon.It also shows that the modified peanuts shell biochar could be a kind of adsorbent with application prospect.