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煤系高岭石复合材料的制备及其吸附性能的研究

Preparation of coal kaolinite composites and study of adsorption properties

  • 摘要: 工业废水中Pb(Ⅱ)和煤基固废会对生态环境造成极大破坏,研究Pb(Ⅱ)高效去除技术和煤基固废的高值化利用具有重要意义。提出以改性煤基高岭石嫁接壳聚糖新型复合材料CK-CTAC/CTS为吸附剂,采用吸附法实现对废水中Pb(Ⅱ)的去除。以煤系高岭石(RK)为原料,二甲基亚砜(DMSO)、甲醇(MeOH)和十六烷基三甲基氯化铵(CTAC)为插层剂,经3次插层获得改性高岭石(CK-CTAC),通过共聚反应嫁接壳聚糖(CTS),制备CK-CTAC/CTS复合材料,并用批量试验法研究其对Pb(Ⅱ)的吸附性能和机理。XRD、SEM、BET分析表明,插层物CK-D、CK-M、CK-CTAC插层率分别达到93.8%、75.1%和66.5%,CK-D、CK-M插层前后形貌未发生明显变化,CTAC大分子结构和超声仪器能量输入使高岭石层间形貌变为管状,孔隙增多,比表面积增大4倍。XPS、FTIR结果表明,CK-CTAC/CTS具有丰富的官能团,可以有效吸附Pb(Ⅱ)。25 ℃溶液、pH=6时,经过100 min即接近吸附平衡状态。改性高岭石优良的空间结构和暴露的官能团为吸附提供了更多活性位点,壳聚糖丰富的氨基和羟基可以对Pb(Ⅱ)螯合吸附,协同促进,复合材料吸附性能高于单独的壳聚糖或高岭石。吸附动力学和热力学表明,复合材料对Pb(Ⅱ)离子的吸附符合准二级动力学模型和Langmuir等温线模型,是一种单分子层、化学吸附为主的吸热自发过程,最大平衡吸附容量为195.37 mg/g。吸附试验证实了CK-CTAC/CTS在废水中去除Pb(Ⅱ)的适用性,为工业上去除Pb(Ⅱ)提供了一种高效可行的方法。

     

    Abstract: Pb(Ⅱ) in industrial wastewater and coal-based solid waste can cause great damage to the ecological environment, and it is of great significance to study the efficient removal technology of Pb(Ⅱ) and the high-value utilization of coal-based solid waste. In this paper, we propose to use modified coal-based kaolinite grafted with chitosan novel composite material CK-CTAC/CTS as the adsorbent to realize the removal of Pb(Ⅱ) from wastewater by adsorption method. Coal kaolinite (RK) was used as raw material, dimethyl sulfoxide (DMSO), methanol (MeOH) and cetyltrimethylammonium chloride (CTAC) were used as the intercalating agents, and modified kaolinite (CK-CTAC) was obtained by three times intercalation, and CK-CTAC/CTS composite was prepared by grafting chitosan (CTS) through the copolymerization reaction, and the batch experimental method was used to study the Pb(II) XRD, SEM and BET analyses showed that the intercalation rates of CK-D, CK-M and CK-CTAC reached 93.8%, 75.1% and 66.5%, respectively, and the morphology did not change significantly before and after the intercalation of CK-D and CK-M, while the large molecular structure of CTAC and the energy input of ultrasonic instrument changed the interlayer morphology of kaolinite into tubular, with an increase in pore space and a 4-fold increase in surface area compared with that of the CK-CTAC. XPS and FTIR results showed that CK-CTAC/CTS has rich functional groups, which can effectively adsorb Pb(II), and the adsorption equilibrium was approached after 100 min at a solution pH of 6 at 25 ℃. The excellent spatial structure and exposed functional groups of modified kaolinite provided more active sites for adsorption, and the abundant amino and hydroxyl groups of chitosan could chelate and adsorb Pb(II), which synergistically promoted the adsorption performance of the composites higher than that of chitosan or kaolinite alone. The adsorption kinetics and thermodynamics showed that the adsorption of Pb(II) ions by the composites conformed to the quasi-secondary kinetic model and Langmuir isotherm model, and it was a monomolecular-layer, chemisorption-dominated, heat-absorbing and spontaneous process with a maximum equilibrium adsorption capacity of 195.37 mg/g. The adsorption experiments confirmed the applicability of the CK-CTAC/CTS to the removal of Pb(Ⅱ) in wastewater for the industrial removal of Pb(II) provides an efficient and feasible method.

     

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