| With the development of society, especially the development of industry, heavy metal pollution has become more and more serious environmental problems. Heavy metal ions in environment waters are strong toxic, easy accumulation through the food chain and difficult to degradate. They cause serious threat to the health of human beings and the ecological environment. At present, the heavy metal pollution in our country mainly comes from heavy metal mining, smelting, machining process. The process can cause a lot of heavy metal and they pollute the atmosphere, water and soil. Heavy metal pollution mainly displays in water pollution. The extent of the hazards depends on the concentration of metal ions and their valence and form, so speciation analysis of heavy metals in water and removal of heavy metal from water are very important. The existing form of heavy metal ions cannot be detected directly by the atomic emission (AES) and atomic absorption (AAS) instrument, and needs to go through a sample pretreatment, enrichment and separation process. Common technologies used to remove heavy metal ions are chemical precipitation, ion exchange, solvent extraction and adsorption method. Adsorption method has been widely used, because of simple operation and low cost. Absorbent material is the key substance in the process of absorption.In recent years, mesoporous materials are widely used as absorbents due to theirs high surface area, nano size and easily surface functionalization. Especially, M41S series of mesoporous materials have become the ideal absorbent for removing heavy metal ions in waste water. As a kind of M41S series of mesoporous materials, MCM-48with two independent three-dimensional pore systems and excellent transmission performan, is easy to transmit the molecule obstacles. Therefore it is a kind of very good separation and enrichment material. MCM-48has larger specific surface area, surface easily modified by organic group, even pore size distribution and thermal stability. MCM-48has been successfully used for adsorption heavy metal ions by researchers. In order to improve the adsorption capacity of goal pollutant, scholars have studied improvement of the preparation method or introducing silane coupling agent to mesoporous materials for surface modification.The objective of this paper is the inorganic and organic functionalized MCM-48mesoporous materials synthetized through the direct synthesis or co-condensation method, and they are used for separation and removal of heavy metal ions as absorbents. Based on the previous reports, four innovative works were carried out in this paper. Concrete research conclusions are as follows:(1)With cetyltrimethylammonium bromide (CTAB) and poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol)(P123) as co-template, tetraethylorthosilicate (TEOS) as silica source, sodium aluminate as aluminum source, mesoporous materials Al-MCM-48were directly synthesized by hydrothermal method. The obtained products were characterized by XRD, N2sorption-desorption. The effects of the experimental parameters, including pH, Al-MCM-48amount, eluent concentration and interfering ions on separation and determination of Cr(Ⅲ) and Cr(Ⅵ) were investigated. As a result, Cr(Ⅲ) was selectively adsorbed on Al-MCM-48in the pH from4to10, while Cr(Ⅵ) remained in Solution. The sorbed Cr(Ⅲ) ions were desorbed with3.0mol/L HCl. The detection limits of this method were19μg/L for Cr(Ⅲ) and12μg/L for Cr(Ⅵ), and the relative standard deviations were found to be less than3.5%(n=10, C=2mg/L). The proposed method is high selective for inorganic chromium speciation analysis of environmental water.(2)Thiol-functionalized MCM-48(SH-MCM-48) was synthesized by co-condensation method, with co-template of cetyltrimethylammonium bromide (CTAB) and nonionic poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer (Pluronic P123). The resulting material was characterized by XRD, FT-IR, thermogravimetric analysis and SEM. The potential of SH-MCM-48for adsorption Zn(Ⅱ) from aqueous solution was examined. Batch adsorption studies carried out to investigate the effect of experimental parameters including pH, metal ions concentration and adsorption time. The maximum adsorption capacities of Zn(Ⅱ) onto SH-MCM-48were30.12mg/g,34.01mg/g and38.02mg/g at the temperature of303K,313K and323K, respectively. The adsorption kinetics data were found to follow the pseudo-second-order kinetic model, and adsorption isotherms were fitted well with Langmuir and Freundlich models.(3)Bi-functional MCM-48modified with3-[2-(2-Aminoethylamino)ethylamino] propyl-trimethoxysilane and3-mercaptopropyltrimethoxysilane was synthesized by co-condensation method, and was characterized by XRD, FT-IR spectrum and thermogravimetric analysis techniques. Batch adsorption studies of Zn(Ⅱ) on bi-functional MCM-48were investigated. The effect of experimental parameters including pH, temperature and adsorption time was studied, and the research results indicated the experimental data were fitted to Langmuir and Freundlich isotherm models, and the Langmuir equation showed better correlation with the experimental data than the Freundlich. The adsorption kinetics data were found to follow the pseudo-second-order kinetic model.(4)Using cetyltrimethylammonium bromide (CTAB) and nonionic poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer (Pluronic P123) as co-template, tetraethylorthosilicate (TEOS) as silica source, amino functionalization MCM-48(NH2-MCM-48) was synthesized by co-condensation method. The existence of amino group on NH2-MCM-48proved by FT-IR spectrum, amino content of NH2-MCM-48was determined by thermogravimetric analysis. Adsorption performance of heavy metal ion Zn(Ⅱ), Mn (Ⅱ), Cr (Ⅲ) and Cr (Ⅵ) on NH2-MCM-48was researched, and NH2-MCM-48has good adsorption effect of the four metal ions. Moreover, the adsorbent was applied in environmental water samples. |
PDF Full Text Request