Preparation Of Manganese Loaded Activated Carbon And Its Adsorption Of Cr（Ⅵ）

With the vigorous development of social industrial technology,the problem of heavy metal wastewater being discharged in large quantities and difficult to be biodegraded has become increasingly prominent,as one of the representative pollutants,Cr(VI)poses a serious threat to human health and ecological stability,which is one of the focuses in the field of water pollution control today.In this paper,on the basis of in-depth investigation of current Cr(VI)treatment technology in water,manganese loaded activated carbon was prepared with granular activated carbon as the basic material,optimize the preparation of manganese loaded activated carbon and characterize it.Then,the adsorption method was used to study the removal of Cr(VI),the effects of environmental factors on the adsorption process was analyzed,the regeneration performance and adsorption mechanism of manganese loaded activated carbon were finally investigated.The equilibrium adsorption capacity of the adsorbent materials was used as the evaluation index,based on the results of single factor test,the effects of immersion time,immersion concentration,calcination temperature and calcination time on the adsorption performance of manganese loaded activated carbon were analyzed by orthogonal test method.The adsorption performance of manganese loaded activated carbon was the best when the immersion time was 7 hours,immersion concentration was 0.15mol/L,calcination temperature was 450℃,calcination time was 2 hours.The adsorption materials before and after modification was characterized by the X-ray diffraction analysis(XRD)and Boehm tradition analysis.It was confirmed that manganese dioxide was successfully loaded on the surface of granular activated carbon and the total amount of acid oxygen-containing functional groups increased,which meant modification was successful.The effects of initial concentration,adsorption time,initial p H and the concentration of anions in solution on the adsorption of Cr(VI)by activated carbon before and after modification were studied,and the adsorption performance of two adsorbent materials on Cr(VI)was investigated.The results showed that the adsorption capacity of the two adsorbent materials increased with the initial concentration,increased to the adsorption equilibrium over time,decreased sharply with the rise of p H,and decreased gradually with the increase of the coexisting anion concentration.The Box-Behnken test was used to design the response surface analysis to analyze the interaction between influencing factors.The results show that the initial p H has the most obvious effect on the adsorption capacity of Cr(VI),and the interaction between the initial p H and the concentration is most significant in the adsorption process.The reutilization performance of manganese loaded activated carbon was analyzed.Choose 0.1mol/L HCl solution as the regeneration solvent,after five adsorption and desorption cycles,the equilibrium adsorption capacity of the adsorbent material can still reach more than 80% of the original equilibrium adsorption capacity,indicating that the manganese loaded activated carbon has a certain value for regeneration and reuse.According to the analysis of the adsorption mechanism,the adsorption process of of Cr(VI)by activated carbon before and after modification is more consistent with the Langmuir adsorption isotherm model and the pseudosecond-order kinetic model.The adsorption process is monolayer adsorption,which is mainly chemical adsorption.In addition to intra-particle diffusion,it also exists other control mechanisms,and the modified adsorption material is more conducive to the progress of the adsorption reaction under the same adsorption conditions.