光化学还原过程中纳米TiO_2表面Hg(Ⅱ)的吸附与脱附  

Adsorption and desorption of Hg(Ⅱ) at surface of nanocrystalline TiO_2 during photochemical reduction process

作　　者：司士辉[1] 杨政鹏[1] 刘波[2] 

机构地区：[1]中南大学化学化工学院,长沙410083 [2]深圳大学应用化学系,深圳518060

出　　处：《中国有色金属学报》2005年第9期1465-1470,共6页The Chinese Journal of Nonferrous Metals

基　　金：国家高技术研究发展计划资助项目(2001AA218041);国家自然科学基金资助项目(20475065)

摘　　要：采用石英晶体微天平现场技术研究了Hg(Ⅱ)离子在纳米TiO2表面的吸附及光化学还原过程。结果表明:Hg(Ⅱ)离子借助于纳米TiO2表面羟基发生吸附,吸附平衡常数约为3.9×105L/mol,且Hg(Ⅱ)离子的吸附量受溶液的pH值、浓度和共存阴离子的影响;在pH值为4的HgCl2溶液中,Hg(Ⅱ)离子在纳米TiO2上的饱和吸附量约为0.85 mmol/g;在UV光照射下,初始阶段TiO2表面水光解产生的质子可使吸附的Hg(Ⅱ)离子从TiO2表面脱附下来,而且Hg(Ⅱ)浓度和pH值越大,脱附现象越明显;随后Hg(Ⅱ)光还原沉积逐渐占主导地位,且光沉积速率受Hg(Ⅱ)浓度、溶液pH值和有机物加入的影响。In-situ technique of quartz crystal microbalance （QCM） was used to investigate the adsorption and the photochemical reduction process of Hg（ Ⅱ ） at the surface of nanocrystalline TiO2. The results show the Hg（ Ⅱ ） is adsorbed onto the surface of nanocrystalline TiO2 by hydroxyl groups, and the adsorption equilibrium constant is about 3.9 ×10^5 L/mol based on the pseudo-first-order kinetic model. The adsorption amount of Hg（ Ⅱ ） at the surface of TiO2 is affected by pH value, concentration of Hg（ Ⅱ ） and coexisting anions, and the saturated adsorption amount of Hg（ Ⅱ ） is approximately 0. 85 mmol/g at pH of 4. During the initial stage of UV illumination, the protons produced in photodegradative reactions of water can cause the desorption of adsorbed Hg（ Ⅱ ） from the surface of TiO2. The degree of desorption increases with the increase of both the concentration of Hg（ Ⅱ ） and pH value of solution. Then, the photochemical deposit reaction of Hg from the solution strengths and the rate of Hg photodeposition are influenced by the concentration of Hg（ Ⅱ ）, pH value and added organics.

关 键 词：纳米TIO2 吸附 光化学还原 石英晶体微天平 

分 类 号：O614.243[理学—无机化学]