关键词: 有机膨润土;表面活性剂;硅烷偶联剂;苯酚;吸附;动力学

Abstract: A novel Organobentonite was prepared by modifying calcium bentonite using cationic surfactant hexadecyltrimethyl-ammonium chloride(HTMAC)as intercalation agents and grafting with silane coupling agent(KH570).The Organobentonite was characterized and analysed with Fourier transform infrared(FT-IR),X-ray diffraction(XRD), scanning electron microscope(SEM), thermogravimetric differential thermal analysis(TG-DTA)and Brunauer-Emmett-Teller(BET).The results show: the modified reagent(HTMAC)has been intercalated to the layer of bentonite,and the d001values increase from 1.533 nm to 2.342 nm.The phenol molecule can be adsorbed in multiple layers or obliquely inserted into the layer of organobentonite(Diameter of phenol is 0.69nm).From the TG-DTA curve,It shows the organobentonite exhibited there steps of weight loss.The adsorbed water was lost at T<225℃,corresponding to 2.9%.A mass lose(15%)in the temperature range of 490 ℃ due to the decomposition of HTMAC and KH570.Another mass loss(2%)centered in the range of 490-600 ℃due to the dehydroxylation of OH units.The N2adsorption-desorption isotherm of organobentonite exhibited that it belongs to IV isotherm with H3 hysteresis loop, indicating that organobentonite was a mixed microporous/mesoporous material.The specific surface area of purified bentonite and organobentonite were 5.43 m2· g-1and 46.87 m2· g-1respectively.Pore volume of puried bentonite and organobentonite were up to 0.102 cm3· g-1and 0.213 cm3· g-1.Factors affecting the adsorption of phenol(such as pH, equilibrium time temperature, the dosage of adsorbent and initial concentration) were investigated.The highest removal rate of phenol waste water is 79.8%,and the best condition is:dosage of organobentonite 3 g· L-1,adsorption time 60 min,pH 7.2 and adsorption temperature 10℃. The phenol adsorption data gives good fits with Langmuir isotherm model.The parameter factor RL falls between 0 and 1,indicating the adsorption of phenol is favorable.The adsorption process is exothermic with negative ΔH values.The negative ΔS suggested an decrease randomness at the solid-liquid interface during the adsorption process.The spontaneous adsorption depends on the exothermic characteristics of the adsorption process.The adsorption trend follows the pseudo-second order kinetics model.The whole adsorption process was controlled by surface chemical adsorption and intraparticle diffusion.

Key words: organobentonite;surfactants;silane coupling agent;phenol;adsorption;kinetics