【作者】 李元；

【导师】 贾绍义；

【作者基本信息】 天津大学 ， 化学工程， 2013， 博士

【摘要】 砷污染是一个全球性的环境问题，直接影响到饮用水安全，吸附法是去除水中砷的最有效和最常见的一种方法，吸附法除砷的关键是开发高效吸附剂，而高效吸附材料的开发也依赖于对吸附机制的深刻理解。本文较为全面地概述了砷污染治理方法和二氧化钛对砷吸附的研究近况，制备了钛—铁、钛—锰和钛铁/蒙脱土的二氧化钛复合材料，研究了这些复合吸附剂对砷的吸附特性，阐明了砷在二氧化钛复合材料的光促吸附机制。采用水热法合成了锐钛矿型的二氧化钛、两种钛基双金属氧化物、一系列不同铁含量的双金属改性蒙脱土复合物，并通过XRF、XRD、BET、SEM、TEM等分析手段对其微观形貌和结构进行表征。开展了吸附动力学和吸附等温线的实验，考察了pH值、干扰离子、紫外光、羟基等因素对砷在二氧化钛和二氧化钛复合材料上的吸附特性的影响。通过Zeta电位、FTIR、XPS、Raman等微观表征手段对吸附机理进行了研究，构建砷在二氧化钛和二氧化钛复合材料表面的吸附模型。通过XRD、XRF、N2吸附脱附等温线等表征手段确定了材料的最佳制备方法，SEM、TEM、EPR等分析手段表明材料具有较好的微观结构和较大的表面积，有利于砷的吸附。吸附特性实验表明：紫外下As(III)的吸附容量和吸附速率都大大增加了；当pH=2~4，As(V)的吸附容量达到最大值，当pH>4时，吸附容量随pH增大而减少，紫外下As(III)的吸附与As(V)类似，黑暗下As(III)在二氧化钛上的吸附随pH增大而减少；在众多共存阴离子中，因为SiO32-和PO43-与砷酸根具有类似的离子常数和结构，对砷产生了竞争吸附。表面羟基实验表明羟基自由基在As(III)的氧化过程起主要作用。Zeta电位、FTIR和XPS等微观表征证明了As(III)和As(V)分别以单齿和双齿的形式吸附到二氧化钛及其复合材料表面。总的来说，制备的二氧化钛复合吸附剂能将水溶液中砷的含量降到10μg/L以下，满足饮用水的限定值。黑暗条件下，二氧化钛及其复合材料作为单一的吸附剂，紫外光存在的情况下，二氧化钛及其复合材料既是吸附剂也是光催化剂。更多还原

【Abstract】 Arsenic contamination is a global environmental problem, adsorption is one ofthe most effective and common method for the removal of arsenic, and an efficientarsenic adsorbent is also dependent on a deep understanding of the adsorptionmechanism. Recently, nanocrystalline titanium dioxide has been developed foreffective removal of arsenic due to its good photochemical stability, non-toxic, highcatalytic activity for As(III) oxidation. In this study, we make a comprehensive reviewon the application of TiO2and TiO2bifunctional adsorbents for arsenic adsorption.We also make many efforts to understand the the performance of TiO2by eithercombing TiO2adsorbent with good adsorption property in one system or developingbifunctional adsorbents with both great photocatalytic ability and high adsorptioncapacity.Anatase TiO2, two metal mixed oxide Ti-Fe and Ti-Mn binary oxide composites,and a series of titanium and iron pillared montmorillonites (Ti-Fe/MMT) wereprepared by a hydrolysis method and to comprehensively evaluate arsenicadsorption/oxidation on TiO2with and without UV irradiation. The as-preparedsamples were characterized by powder X-ray diffraction (XRD), scanning electronmicroscope (SEM), transmission electron microscope (TEM), and nitrogenadsorption-desorption techniques. After a general characterisation of those adsorbents,the adsorption kinetics and isotherm data were analysed. The effects of pH and theinfluence of coexisting ions on arsenic adsorption were investigated in order tounderstand the mechanism of arsenic adsorption under UV irradiation.XRD, nitrogen adsorption-desorption techniques, electron paramagneticresonance (EPR), SEM, TEM and X-ray fluorescence analyzer (XRF) investigationsrevealed that the TiO2and TiO2bifunctional adsorbents have better surfaceperformance for arsenic adsorption, and the anatase nanoparticles of TiO2in the TiO2bifunctional adsorbents were responsible for As(III) oxidation under UV irradiation.The optimum adsorption capacity on the adsorbent was achieved at pH below7forAs(V) and at neutral pH for As(III). Among all the common coexisting ionsinvestigated, silicate and phosphate ions were the greatest competitor with arsenic foradsorptive sites on the adsorbent. Zeta potential and Fourier transform infrared (FTIR)analysis indicated that the hydroxyl groups on the TiO2and TiO2bifunctionaladsorbents surface were involved in arsenic adsorption, while X-ray photoelectronspectroscopy (XPS) provided further evidence for the involvement of hydroxyl groups in the sorption and the formation of monodentate and bidentate complexes on theadsorbent surface. Furthermore, the XPS and Raman analysis confirmed that the Mninvolved in the oxidation-sorption of As(III). The study suggests that Ti-Fe and Ti-Mn binary oxide composites were effective adsorbent for arsenic removal due to itsphotocatalytic oxidation property and the presence of high affinity surface hydroxylgroups. The good reusability of Ti-Fe/MMT also indicated that the Ti-Fe/MMT was avery promising adsorbent for arsenic removal from arsenic contaminated water.After adsorbed with TiO2and TiO2bifunctional adsorbents, the final arsenicconcentration in solution below10μg/L, and meet the arsenic standard in drinkingwater. The results suggest that the TiO2and TiO2bifunctional adsorbents canfunctions as both photocatalyst and adsorbent in the presence of UV light, but itworks only as adsorbent in the absence of UV light.更多还原