双硫腙包覆钛酸锶钡粉体对水中铅的吸附行为

Adsorption Behavior of Barium-Strontium Titanate Powder Coated by Dithizone for Lead Ion in Water

用草酸化学共沉淀法合成了钛酸锶钡(BST)粉体,以双硫腙为表面修饰剂,采用静态浸渍法对钛酸锶钡粉体进行表面包覆修饰,制备出新型固态粉体吸附剂.利用X射线衍射(XRD)、扫描电镜(SEM)和傅立叶变换红外光谱(FTIR)进行了表征.研究了该吸附剂对水中铅的吸附行为.结果表明:双硫腙通过与钛酸锶钡表面羟基形成氢键作用包覆于该粉体上;当吸附介质pH值大于4时,该吸附剂对水中的铅有较强的吸附能力;室温下,5min内吸附达到平衡.其吸附行为符合Langmuir吸附等温模型和HO准二级动力学方程式,吸附焓变(△H)为19.42kJ·mol-1,活化能(Ea)为22.187kJ·mol-1,该吸附过程是吸热的物理过程.吸附在双硫腙包覆钛酸锶钡粉体上的铅,可用1mol·L-1的硝酸溶液进行洗脱.建立了吸附富集、火焰原子吸收法测定水中铅的新方法,应用于地表水和自来水中铅的测定,取得了令人满意的结果.

Barium-strontium titanate （BST） powder was prepared by using an oxalate coprecipitate method and was modified by dithizone coating through a maceration method, gaining a new sort of adsorbent. XRD, SEM and FT-IR analyses were used to characterize the powder and surface modification. The adsorption behavior of lead on the BST powder coated by dithizone was investigated. The results showed that the dithizone was coated on the BST powder through hydrogen bonding between the hydroxyl groups and oxygen atoms on the surface of the BST and dithizone. The lead ion in water could be adsorbed quantitively on the dithizone coated BST when the pH exceeded 4.0, and the adsorption equilibrium could be obtained in 5 min at room temperature. The adsorption behavior followed a Langmuir adsorption isotherm and a pseudo-second-order kinetic model. The enthalpy of adsorption （AH） was 19.42 kJomol 1 and the activation energy （Ea） was 22.187 kJomo1-1 for the adsorption. The values show that the adsorption of lead ion by dithizone coated BST powder is an endothermic process. The lead ion adsorbed on the BST powder coated by dithizone could be completely eluated using 1 mol·L^- 1 HNO3. A new method for determination of trace lead ion in water based on this dithizone coated BST powder separation/preconcentration and flame atomic absorption spectrometry （FAAS） determination was proposed. The method has been applied to the determination of trace lead ion in water samples with satisfactory results.