Study On Adsorption Of Triclosan Onto HDTMA Modified Zeolite

Triclsan (TCS), a typical contaminant of pharmaceuticals and personal care products(PPCPs), is commonly used as additives in personal care products such as cosmetics andcleaning supplies. TCS have become a kind of ubiquitous pollutants in the environment due tothe widespread use of these products. Natural zeolite is an emerging non-metallic mineralresource in the world today. The excellent properties of adsorption and ion exchange havemade it a good material in the treatment of the ‘three wastes’.In this study, four different HDTMA-zeolites were prepared by a simple solid-liquidadsorption method. The modifier of hexadecyl trimethyl ammonium bromide (HDTMA) wasadded equal to50,100,150and200%external cation exchange capacity (ECEC) of rawclinoptilolite, which were then denoted as S50, S100, S150, and S200respectively and werecharacterized by Elementary analysis（EA）, Fourier transform infrared spectroscopy (FTIR),X-ray diffraction (XRD), Brunauer–Emmett–Teller surface measurements (BET) and Zetapotential measurements. Functioned performances, mechanism and influence rules of thesorption of TCS onto HDTMA modified zeolite were investigated by single-factor batchexperiments. The desorption of TCS and HDTMA were investigated further in order to provethe safety of this sorbent.This work provided theoretical foundation of application of HDTMAmodified zeolite technology for triclosan contaminant in wastewater. The main conclusionsare drawn as follows:1. There was no organic carbon in raw zeolite and the organic carbo on HDTMAmodified zeolites increased with increase of HDTMA loading. In addition, the HDTMA+wasadsorbed mainly on the surface and did not change the crystal structure of the raw zeolite.Increasing amount of HDTMA+decreased the specific surface but increased the positivecharge on the surface of the HDTMAmodified zeolites.2. The adsorption equilibrium of TCS on raw zeolite and HDTMA modified zeolites canbe reached within24h and2hours, respectively. Sorption capacities of TCS onto raw zeolite,S50, S100, and S150decreased with increase of pH. The optimum pH for sorption wasdetermined as7.0. The S200, however, was more efficient at higher pH. Higher ionic strengthis more favorable for the sorption of TCS by the sorbents at pH7and ionic strength 0.001~0.5M. Lower temperature was preferred in the sorption of TCS. Sorption capacityincreased with increase of HDTMA loading while the stability decreased. So100%ECECloading would be appropriate in the sense of sorption efficiency, cost and stability.The sorption behavior of TCS onto HDTMAmodified zeolites can be well fitted by linearisotherm (R2>0.98). The dominant mechanism of the sorption is partitioning, electrostaticinteraction and weak surface adsorption were supporting. Functions of thermodynamics at25oC~45oC indicated that the adsorption of triclosan on HDTMA modified zeolites was anexothermic process and there was just weak attraction between TCS and the sorbents. Thesorption process of TCS onto HDTMA modified zeolites can be well described bypseudo-second order kinetic model (R2>0.999).