( 1. 中南大學(xué) 化學(xué)化工學(xué)院, 長(zhǎng)沙 410083;
2. 深圳大學(xué) 應(yīng)用化學(xué)系， 深圳 518060)
摘 要: 采用石英晶體微天平現(xiàn)場(chǎng)技術(shù)研究了Hg(Ⅱ)離子在納米TiO2表面的吸附及光化學(xué)還原過(guò)程。 結(jié)果表明： Hg(Ⅱ)離子借助于納米TiO2表面羥基發(fā)生吸附， 吸附平衡常數(shù)約為3.9×105 L/mol， 且 Hg(Ⅱ)離子的吸附量受溶液的pH值、 濃度和共存陰離子的影響； 在pH值為4的HgCl2溶液中， Hg(Ⅱ)離子在納米TiO2上的飽和吸附量約為0.85 mmol/g; 在UV光照射下， 初始階段TiO2表面水光解產(chǎn)生的質(zhì)子可使吸附的 Hg(Ⅱ)離子從TiO2表面脫附下來(lái)， 而且Hg(Ⅱ)濃度和pH值越大, 脫附現(xiàn)象越明顯； 隨后Hg(Ⅱ)光還原沉積逐漸占主導(dǎo)地位， 且光沉積速率受Hg(Ⅱ)濃度、 溶液pH值和有機(jī)物加入的影響。
關(guān)鍵字: 納米TiO2； 吸附； 光化學(xué)還原； 石英晶體微天平
（ 1. School of Chemistry and Chemical Engineering, Central South University, Changsha 410083, China;
2. Department of Applied Chemistry, Shenzhen University,
Shenzhen 518060, China）
Abstract: 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 3.9×105 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.
Key words: nano titanium dioxide; adsorption; photoreduction; quartz crystal microbalance
