Abstract
In this study, the modified zeolite with certain hydrophobicity was prepared by modifying natural zeolite by the silane coupling agents such as vinyltrimethoxysilane (VTMO), trimethoxysilane (TMS) and trimethylchlorosilane (TMCS). The modified zeolite has a higher hydrophobicity and adsorption capacity than natural zeolite while ensuring the advantages of natural zeolite, which is more conducive to the adsorption of organic pollutants from aqueous solution. The adsorption experiment on naphthalene in aqueous solution shows that the modified zeolite has a stronger adsorption capacity. In the adsorption thermodynamics experiment, the isothermal adsorption models such as Freundlich and Langmuir can better describe the adsorption of naphthalene on modified zeolite, but the isothermal adsorption model Freundlich has a higher correlation. At 303K, the static adsorption capacity is 339μg/g. The kinetic analysis shows that the adsorption of naphthalene on modified zeolite conforms to the quasi-second order kinetic model.
Highlights
Polycyclic aromatic hydrocarbons (PAHs) belong to a kind of typical persistent organic pollutants in the environment because of its strong teratogenic, carcinogenic and mutagenic effects [1], and once they enter the environment and ecology, they may be spread to the city’s domestic water supply system through natural circulation so that the residents’ physical safety may be harmed [2], it is greatly significant for pollution prevention in the water environment in China to effectively reduce the content of PAHs in wastewater
Sorption band of Si(Al)-O gene group was presented in the range of 400 - 550 cm−1 and 950 - 1200 cm−1, but in the infrared spectrum of modified zeolite, there were two obvious absorption peaks of CH bond in the range of 2800 - 3000 cm−1, as shown in the red dotted line frame in figure, there was no obvious absorption peak in the range of the infrared spectrum of natural zeolite, indicating that the three organic modifiers had been successfully loaded on the surface of the zeolite and the shelf structure of the zeolite itself had not been changed
The weight loss of natural zeolite was mainly for the evaporation and escape of the absorbed water, crystal water, structural water and zeolite water within the zeolite with different temperatures, and for three organic modified zeolites, in addition to moisture evaporation, a part of modifiers would be lost, the results showed that the modified zeolite had been successfully loaded on the modifier
Summary
Polycyclic aromatic hydrocarbons (PAHs) belong to a kind of typical persistent organic pollutants in the environment because of its strong teratogenic, carcinogenic and mutagenic effects [1], and once they enter the environment and ecology, they may be spread to the city’s domestic water supply system through natural circulation so that the residents’ physical safety may be harmed [2], it is greatly significant for pollution prevention in the water environment in China to effectively reduce the content of PAHs in wastewater. The common methods for removing PAHs in aqueous solution at home and abroad include biodegradation, advanced oxidation and adsorption [3], among which the adsorption method, with the advantages of simple operation, high efficiency and low cost, has been one removal method[4] of polycyclic aromatic hydrocarbons in aqueous solution concerned by researchers recently. Natural zeolites are aluminosilicate minerals; it has rich reserve and low price in China. It has good adsorption performance and cation exchange performance because of its huge specific surface area and abundant pore structure [5]. Because the natural zeolite shows stronger hydrophilicity, poorer adsorption performance of organic compounds and poorer adsorption capacity of the anion [6], the research on applying surfactant or silane coupling agent in surface modification of natural zeolite to make up for the lack of natural zeolite has become a hot spot in recent years [7]-[12]
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