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以小麦秸秆和菱铁矿为原料,在500℃下热处理改性,制备了一种C-Fe_3O_4复合材料.采用FTIR、XRD、SEM、BET、磁化率仪对C-Fe_3O_4复合材料(以下统称复合材料)进行表征.考察了接触时间、初始pH、初始Cd~(2+)浓度、离子强度对Cd~(2+)去除率的影响,结合吸附前后表征结果分析了复合材料对Cd~(2+)的吸附机制.结果表明:复合材料及单独煅烧制备的小麦秸秆炭的比表面积分别为23.38 m~2·g~(-1)和7.20 m~2·g~(-1),孔容积分别为1.04×10-1cm~3·g~(-1)和2.23×10-2cm~3·g~(-1),平均孔径分别为17.74 nm和12.38 nm;红外光谱显示复合材料和小麦秸秆炭表面富含羧基、羟基等具有金属离子吸附活性的官能团;磁化率测试结果显示复合材料的质量磁化率为42 900×10~(-8)m~3·kg~(-1).复合材料对Cd~(2+)的吸附动力学用准二级动力学模型拟合度最好;吸附等温线符合Freundlich模型;pH在3.0~6.0之间,吸附容量随pH增大而升高,pH在6.0~9.0之间,吸附容量趋于稳定;pH在4.0~9.0之间,解析量随pH增大而减少;离子强度从1 mmol·L~(-1)增至100 mmol·L~(-1),Cd~(2+)的吸附容量略有减少,解析率由0.51%提升至8.5%;说明复合材料主要通过表面络合作用及离子交换去除溶液中的Cd~(2+).此外,复合材料的磁化性能使其在固液分离方面比一般的吸附材料具有很大优势.
A kind of C-Fe_3O_4 composite was prepared by heat treatment at 500 ℃ with wheat straw and siderite as raw materials.The C-Fe_3O_4 composites (hereinafter referred to as composite) were characterized by FTIR, XRD, SEM, BET and magnetic susceptibility The effects of the contact time, the initial pH, the initial Cd 2+ concentration and the ionic strength on the removal of Cd 2+ were investigated. The effect of the composite on the Cd ~ (2) +) Adsorption mechanism.The results showed that the specific surface area of the composite carbon and wheat straw carbon prepared separately calcined were 23.38 m 2 · g -1 and 7.20 m 2 · g -1, respectively, and the pore volume (-1) and 2.23 × 10-2cm ~ 3 · g -1, respectively. The average pore diameters were 17.74 nm and 12.38 nm, respectively. The IR spectra showed that the composites and wheat straw The surface of carbon is rich in functional groups such as carboxyl and hydroxyl which have metal ion adsorption activity. The magnetic susceptibility test results show that the magnetic susceptibility of the composites is 42 900 × 10 -8 m 3 · kg -1. The adsorption kinetics of Cd 2+ was best fitted by quasi-second-order kinetic model. The adsorption isotherm fitted the Freundlich model. The adsorption capacity increased with the increase of pH between pH 3.0 and 6.0. The pH The adsorption capacity tends to be stable between 6.0 and 9.0; the pH value is between 4.0 and 9.0, the amount of analyte decreases with the increase of pH; the ionic strength increases from 1 mmol·L -1 to 100 mmol·L -1, 1), the adsorption capacity of Cd 2+ slightly decreased, and the resolution increased from 0.51% to 8.5%. The results showed that Cd 2+ in the solution was mainly removed by surface complexation and ion exchange. The magnetization properties of composite materials have great advantages in the solid-liquid separation over the common adsorbents.