Study On Removal Properties Of Sulfidation And Supported Modified Zero-valent Iron For As(Ⅴ) And Cr(Ⅵ)

With the rapid development of chemical fertilizer,leather,electroplating,mining,textile and other industries,wastewater containing arsenic and chromium are discharged in violation of regulations,aggravating the complexity and instability of heavy metal pollution.Therefore,it is important to purify arsenic and chromium with adopting economic and effective strategies.In this paper,a novel adsorbent,ZSM-5 zeolite supporting sulfide zero-valent iron(S-n ZVI@ZSM-5)was prepared by liquid phase reduction method.The structure and adsorption mechanism of adsorbent was investigated by various characterization methods(BET,SEM,TEM,XRD,FTIR and XPS)in different pollution system.In addition,the adsorption capacity of the uptake of Cr(VI)was analyzed from the physic-chemical property of S-n ZVI@ZSM-5.The main conclusions of this study could be proposed as follows:(1)The removal performance of arsenic by S-n ZVI@ZSM-5 in copper-containing wastewater was analyzed.The result showed that the addition of sulfur can decrease iron leaching from 7.68 mg/L to 1.95 mg/L and increase As(V)removal percentage from 89.10%to94.50%;Moreover,the presence of copper in the system played a positive role in removing As(V)at a Cu/As concentration ratio ranging from 0 to 20,while a negative influence was observed when Cu/As concentration ratio was above 20.The excellent fit result was displayed between the the experimental data and Langmuir adsorption isotherm,and the maximum capacity was 204.36 mg/g.(2)The adsorption performance of S-n ZVI@ZSM-5 to As(V)and Cr(VI)was investigated.Compare to single system,the maximum adsorption capacity of S-n ZVI@ZSM-5 for As(V)and Cr(VI)decreased by 13.01%and 63.08%,respectively,due to competition adsorption process.Then,aging time of S-n ZVI@ZSM-5 was assessed and the removal performance of As(V)and Cr(VI)maintained 99.14%and 81.70%of freshly prepared S-n ZVI@ZSM-5 capacity after 5 days aging,respectively,which indicated that the adsorbent had excellent stability.Through the analyses of XPS,the adosorption mechanism of As(V)and Cr(VI)were(i):electrostatic attraction;(ii):reduction;(iii):co-precipitation.(3)The influence of physic-chemical properties of adsorbent on the adsorption process was further studied.The results of adsorbents characterization showed that large particle size can conducive to Fe~0 deposited well on the ZSM-5surface.Simultaneously,we can put forward an important explanation was that the exposed(200)plane of Fe~0 did not as active as(110)plane resulting in inhibition of electron transfer.Small crystalline size,large lattice constant,high crystallinity and Fe~0 content jointly contributed to enhance the activity of adsorbent which facilitated the electron transfer from adsorbent to Cr(VI).More importantly,new regenerant was introduced in regenerative test to successfully improve the regeneration performance for uptake of Cr(VI),which made the removal percentage of Cr(VI)was approximately 80.00%even after ninth cycle.