Adsorption Study Of Cr(?) From Simulated Wastewater On Walnut Shell Carbon

In this paper,The sources,harmfulness and the commonly used processing methods of chromium containing wastewater were discussed in this paper.Xinjiang walnut shell was selected as raw material that crushed,washed and dried to carbonize to prepare the normal shell carbon in common atmosphere.The walnut shell was dipped in the solution of ZnCl2 with a certain quality score,which to prepare the zinc chloride pore-forming shell carbon in nitrogen atmosphere.The magnetic shell carbon was prepared by chemical co-precipitation method which Fe Cl3 and FeCl2 were co-precipitated with nitrogen shell carbon at a certain molar ratio,and the treatment of low concentration wastewater containing Cr(?)by three kinds of shell carbons was studied.The adsorption effect of adsorbent dosage,initial pH value,adsorption time,adsorption temperature and initial concentration were studied.The adsorption effect was compared with that of commercial activated carbon,which has carried on the preliminary discussion on its adsorption mechanism combined with adsorption isotherms and adsorption kinetics.The surface structure of the three kinds of shell carbons were characterized by SEM,BET and FTIR modern technology.Adsorption experiments showed that: Treating 50 mL simulated wastewater whose initial concentration of Cr(?)was 20 mg/L with three kinds of shell carbons.(1)When the normal shell carbon dosage of 16 g/L,the initial pH at 2.0,the oscillation intensity with 150 r/min,temperature at 25?,after 180 min,the adsorption process reached to the adsorption equilibrium,respectively,the removal rate of Cr(?)could be up to 98.7%,the effluent concentration of 0.27 mg/L.(2)When the zinc chloride pore-forming shell carbon dosage of 10 g/L,the initial pH at2.0,the temperature was controlled 25 ?,after 180 min,the adsorption process reached to the equilibrium,respectively,the removal rate of Cr(?)was to 98.8%,the effluent concentration of 0.25 mg/L.(3)When the magnetic shell carbon dosage of 4 g/L,the initial pH at 2.0,temperature at25?,the oscillation intensity with 100 r/min,after 30 min,the adsorption process reached to the equilibrium,respectively,the adsorption capacity of Cr(?)was to 4.963 mg/g,the effluent concentration of 0.15 mg/L.Therefore,it can be seen that the effluent concentration of Cr(?)which adsorbed by three kinds of shell carbons can meet the discharge standard.The fitting results showed that the Langmuir adsorption isotherm model could better describe the adsorption process of Cr(?)by the normal shell carbon,zinc chloride pore-forming shell carbon and magnetic shell carbon,the maximum adsorption capacity was8.873,15.314 and 39.370 mg/g,respectively.The laboratorial adsorption capacity approach the fitting date,which is belong to monolayer adsorption.The pseudo-second-order model is fitted to describe the adsorption of Cr(?)which used three kinds of shell carbon,the correlation coefficients were 0.9880,0.9964 and 1.0000,respectively.The fitting effect is good that the adsorption process is mainly controlled by chemical adsorption step.The characterization results showed that widely pore size distribution,developed pore structure and large specific surface area of three kinds shell carbon.The particles of zinc chloride play the role of strongly pore-forming and catalytic dehydration during the carbonization process.Although the particles of Fe3O4 generated by chemical co-precipitation method was blocked the micropore of magnetic shell carbon,it didn't affect the adsorption performance.The main functional groups of normal shell carbon and zinc chloride pore-forming shell carbon are O-H,C-O,N-H and C-O-C in the analysis of FTIR,but the magnetic shell carbon has shown the characteristic of Fe-O in addition to the above functional groups,which all involved in the process of adsorption reaction.The desorption experiment showed that three kinds of shell carbon could be regenerated by suitable desorption agent,which can be used as a new type of adsorption material.In order to make full use of three kinds of shell carbon,it should be controlled the desorption regeneration times within the respective regulation as well.The material characterization,adsorption isotherm model and adsorption kinetic model were combined to study the mechanism of Cr(?)on the three kinds of shell carbon.It's presumed that the adsorption process of Cr(?)isn't a single adsorption mechanism,but a result of the interaction of a variety of adsorption mechanisms,which is a complex process controlled by physical adsorption and chemical adsorption,and as chemical adsorption for the main process.It has carried on the simple summary to link of training practice that in order to adapt the developing request of the professional degree in the last chapter of the paper.