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研究了纳米无定型TiO2颗粒对饮用水中低浓度的三价砷As(Ⅲ)吸附行为。纳米TiO2颗粒吸附剂的BET表面积为205 m2/g,计算的BJH吸附平均孔径为4.02 nm(4 V/A)。对起始As(Ⅲ)浓度为150μg/L的模拟含砷水,经过5h的吸附处理后残余浓度不足4μg/L,As(Ⅲ)去除率达到97%。反应起始阶段吸附速率较快,84%的As(Ⅲ)能够在20min内去除。As(Ⅲ)吸附动力学较好地符合拟二级动力学模式。最佳As(Ⅲ)吸附pH为9.3,低于此值,随酸性增加吸附速率有所降低;而高于此值的强碱性pH对吸附有强烈抑制作用。在平衡浓度较低的情形下(10～220μg/L),Lang-muir,Freundlich和Dubinin-Radushkevich(D-R)吸附等温式均可较好拟合吸附行为,但中性和弱碱性条件下更符合Fre-undlich吸附等温式;平衡浓度大于220μg/L,吸附容量随平衡浓度增加而迅速增加,最大吸附容量在低浓度下达到4.79 mg/g。
The adsorption of As (Ⅲ) with low concentration of trivalent arsenic in drinking water by nano-amorphous TiO2 particles was studied. The BET surface area of the nano-TiO2 particle adsorbent is 205 m2 / g, and the calculated average pore diameter of BJH adsorption is 4.02 nm (4 V / A). For the arsenic-contaminated water with initial As (Ⅲ) concentration of 150 μg / L, the residual As concentration was less than 4 μg / L after 5 h adsorption, the As (Ⅲ) removal rate reached 97%. The initial adsorption rate was faster and 84% of As (Ⅲ) could be removed in 20 minutes. The adsorption kinetics of As (Ⅲ) is in good agreement with the pseudo-second order kinetic model. The optimum As (Ⅲ) adsorption pH was 9.3. Below this value, the adsorption rate decreased with the increase of acidity, while the strong alkaline pH above this value had a strong inhibitory effect on the adsorption. The sorption isotherms of Langmuir, Freundlich and Dubinin-Radushkevich (DR) all fit the adsorption behavior better under the condition of lower concentration (10 ~ 220μg / L), but under neutral and weak alkaline conditions The results are in agreement with the Freundlich adsorption isotherm. The equilibrium concentration is greater than 220μg / L. The adsorption capacity increases rapidly with the increase of equilibrium concentration, and the maximum adsorption capacity reaches 4.79 mg / g at low concentration.