AMD污泥复合材料吸附As(Ⅴ)的机制及其影响因素

Adsorption Mechanisms and Effect Factors of As(Ⅴ) by AMD Sludge Composite Material

污泥基吸附剂被广泛用于水和土壤中各种污染物的治理,是资源化利用的有效途径.以酸性矿山废水(AMD)污泥为骨料,玉米秸秆为还原剂,膨润土为载体,采用固相还原法制备污泥复合材料,并比较了不同原料配比和不同煅烧温度制备的复合材料吸附As(Ⅴ)的性能,探究了溶液pH、吸附剂投加量和竞争离子等对材料吸附As(Ⅴ)的影响,使用SEM-EDS、XRD、FT-IR、BET和XPS等分析技术对材料性能进行表征,探讨其吸附机制.结果表明,在900℃时AMD污泥∶玉米秸秆∶膨润土=2∶1∶1制备出的材料吸附As(Ⅴ)效果最好,材料表面生成大量Fe_(3)O_(4)、Fe_(2)O_(3)和Fe^(0)颗粒.该材料对As(Ⅴ)的吸附符合准二级动力学模型和Freundlich吸附等温模型,最大吸附容量为164.5mg·g^(-1),比原始AMD污泥提高了4.4倍.静电吸附、含氧官能团络合作用、铁氧化层的吸附和Fe0释放出Fe^(2+)/Fe^(3+)形成Fe(OH)_(2)/Fe(OH)_(3),与砷酸盐的共沉淀等是复合材料吸附As(Ⅴ)的主要作用机制.

Sludge-based adsorbents are widely used for the treatment of various pollutants in water and soil,which is an effective utilization of resources.Sludge composite material was prepared by the solid-phase reduction method using acid mine drainage(AMD)sludge as the skeletal material,corn stover as the reducing agent,and bentonite as the carrier.The adsorption performance of composite materials prepared with different raw material ratios and different calcination temperatures,as well as the influences of solution pH,material dosage,and competing ions on As(Ⅴ)adsorption,were evaluated.Simultaneously,the adsorption mechanisms of composite materials were discussed by using SEM-EDS,XRD,FT-IR,BET,and XPS.The results showed that the material prepared by the AMD sludge∶corn stover∶bentonite ratio of 2∶1∶1 had the best adsorption performance at 900℃,and a large number of Fe_(3)O_(4),Fe_(2)O_(3),and Fe0 particles were formed on the surface of the material.The adsorption process was well fitted with the pseudo-second-order kinetic and Freundlich models,and the maximum adsorption capacity was 164.5 mg·g^(-1),which was 4.4 times higher than that of the original AMD sludge.The adsorption mechanisms included electrostatic adsorption,complexation of oxygen-containing functional groups,adsorption of iron oxide layer,and co-precipitation of arsenate with Fe(OH)_(2)/Fe(OH)_(3),which was formed by Fe^(2+)/Fe^(3+)release from Fe0,etc.