| At present,the heavy metal pollution has become one of the most popular environmental pollution problem,the researchers pay great attention to the hexavalent chromium pollution,just because it is difficult to control,highly toxic and widely distributed.There have been a lot of research on the treament of hexavalent chromium pollution,although many treaments,the limitations of the treatment methods,the secondary pollution of the process,the high cost of the treatment facility and the process,for these reasons,very few methods has been used in practice.Adsorption is the most common and the most studied method,the key is the choice of adsorbent,there are so many studies on the cheap,high effective adsorbing matters,and the relatively simple and effective modification ways.The raw luffa sponge,a crop waste were used as raw materials,and the ethylenediamine modified method were used to deal with the luffa sponge.Using phosphoric acid activation method preparation of raw materials into activated carbon(AC),using ferric chloride soaking method to modified activated carbon(AC-Fe).Through the research of the adsorption characteristics of adsorption material,to explore the best conditions of adsorption,and by measuring the physical and chemical properties of the activated carbon,activated carbon on adsorption principle of Cr(VI)was obtained.To some degree,the modified luffa sponge improved the removal rate of Cr(VI),the removal rate from 14.62% rises to 84.52%.The external factors on the adsorption process of modified luffa sponge also had certain influence,the condition of weak acid could improve the removal rate of the adsorption process and the adsorption quantity,the removal rateand Qe could reach 96.17% and 9.67mg/g,but dealing with a high concentration of chromium solution,the modified luffa sponge had no significant effect.The activated carbon(AC)prepared from the luffa sponge could remove the Cr(VI)as a adsorbent,greatly improved the removal rate and the maximum adsorption capacity,when the initial concentration of 200mg/L,the maximum Qe was 121.32mg/g,AC could treat the high concentration of Cr(VI)solution.The modified activated carbon(AC-Fe),further improvements in the removal rate and the maximum adsorption capacity were also made,the lower dosing quantity had excellent performance of treating Cr(VI)solution,at the strongly acidic condition,the Qe was 48.28mg/g,and the removal rate was 98.71%.The scanning electron micrograph(SEM),pore size distribution,Brunauer-Emmett-Teller surface area analysis(BET),and Fourier transform infrared spectroscopy(FTIR)was used to investigate the physical and chemical properties of the AC and AC-Fe.The SEM was used to observe the surface characteristics,showed features of porosity and roughness,the change of the surface properties before and after the modification was not explicit.Through the analysis of the BET,AC specific surface area was 834.130m2/g;AC-Fe specific surface area was 834.006m2/g,although the tiny difference in the data,the number of micro-pores increased because of modification.According to the FTIR analysis of before and after the adsorption of activated carbon,the luffa sponge activated carbon had obvious absorption peak intensity and position change after adsorption,these changes showed that adsorption increased acid oxygen-containing functional groups on the surface of the activated carbon,modified on the surface of activated carbon may increase the Fe-O keys,thereby increasing the binding sites of Cr(VI),improved the adsorption effect.The adsorption isotherm,adsorption kinetics and thermodynamics showed that the adsorption process was monolayer adsorption,the adsorption rate limiting factors was the adsorption mechanism and the adsorption process is a spontaneous endothermic reaction. |
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