Preparation Of Iron-coated Activated Carbon Adsorption Materials And The Research On The Adsorption Of Arsenate In Water

Arsenic is a highly toxic element, which is the harmful for humans as well as flora and fauna.The arsenic pollution has been the highlight problem.Based on the development and application of environmental protection material,the iron-coated activated carbon adsorbents were prepared by high temperature evaporation method and constant infiltration method with changing the preparation conditions and the modified material.The best adsorbent was selected from the two methods respectively for adsorption performance research and EDS,SEM, XRD, XPS and FTIR characterization,and the stability of two kinds of best material as well as the iron use efficiency for arsenic were carried on the comparative study.Results show that the best adsorbent of high temperature evaporation method is prepared by 5 m L H2O2 and 2 g Fe SO4·7H2O via the high temperature evaporation for 15 min, marked as Fe(1.39 %)- 15 min- H2O2, 1.39 % is iron content of Fe(1.39 %)- 15 min- H2O2, the same below; the best adsorbent of constant infiltration method is prepared by 10 m L H2O2 and2 g Fe SO4·7H2O via the incipient wetness for 24 h at 100℃, marked as Fe(0.485 %)- 24 h-H2O2.The maximum adsorption capacity of Fe(1.39 %)- 15 min- H2O2 is 2.551 mg/g,with the increase of initial concentration,the adsorption capacity of Fe(0.485 %)- 24 h- H2O2increases;with the increase of temperature,the adsorption capacity of the two kinds of material decrease;the adsorption balance time of Fe(1.39 %)- 15 min- H2O2 and Fe(0.485 %)- 24 h- H2O2 is 24 h 、30 h,respectively; the stability of Fe(1.39 %)- 15 min- H2O2 and the removal rate are very good at p H 4~8;the removal rate and stability of Fe(0.485 %)- 24 h-H2O2 is good at p H 2~10 and 4~12,respectively.The presence of Cl O4-、SO42-、PO43-、Mg2+inhibit the adsorption of Fe(1.39 %)- 15 min- H2O2 for arsenate, especially for phosphate,while the existence of Ca2+ promote the adsorption of arsenate;The presence of SO42-, NO3-, Cl O4-, or PO43-inhibit the adsorption of Fe(0.485 %)- 24 h- H2O2 for arsenate, especially for phosphate,while the existence of Cl-(100 mg/L)、Br O3-、 Ca2 +promote the adsorption of arsenate.The adsorption process of Fe(1.39 %)- 15 min- H2O2 for arsenic is well described by Frundlich mode,but that of Fe(0.485 %)- 24 h- H2O2 is well described by linear model.The adsorption reaction of the two kinds of material is mainly physical adsorption and aspontaneous exothermic reaction.the adsorption process of the two kinds of material is well described by quasi level 2 dynamic model,and the reaction rate is controlled by spread out phase;the desorption rate of that is more than 80 %.By EDS, the Fe atom percentage of Fe(1.39 %)- 15 min- H2O2 is higher than that of Fe(0.485 %)- 24 h- H2O2; the SEM has shown that nano-iron hydroxides are formed on the surface of Fe(0.485 %)- 24 h- H2O2 and that sintering distorted hydroxides are formed on the surface of Fe(1.39 %)- 15 min- H2O2; by FTIR, XRD and XPS, amorphous Fe OHSO4 and Fe OOH are formed on the two kinds of modified adsorbent surface,and ferrous iron are found on that,too; the iron use efficiency of adsorbent by infiltrating method is much higher than that of high temperature evaporation method;the stability of Fe(0.485 %)- 24 h-H2O2 is better than that of Fe(1.39 %)- 15 min- H2O2,which indicated the iron efficiency,and stability are effected by preparation method.