Studies On Preparation And Performance Of Lead Ion Adsorbent

Heavy metals contamination is very serious in our country, its pollution to waterand food does great harm to people’s health.The current research has focused on the fastand efficient adsorption materials for trace heavy metals in environmental protectionfield. The molecular imprinting technology has unique advantages such as highspecificity, high selectivity, good stability and recyclability, and it also can extract targetmolecules from complex samples accurately, so it has become one of the most widelyused techniques in the field of separation and enrichment materials in recent years.Electrochemical analysis technique and molecular imprinting way were used to preparemolecular imprinted adsorbent materials for Pb²⁺in this study. And then, the magneticadsorbent was synthetized based on the characteristics of the imprinted adsorbent.The main contents were as follows:①Electroanalytical chemistry had been widely used in the detection of traceions due to its advantages such as its high sensitivity, good selectivity and so on. In thiswork, anodic stripping voltammetry （ASV） was used to determine Pb²⁺and Cd²⁺withdithizone as modifier to modify glassy carbon electrode. The effects of medium, pH,potential and quiet time on the peak current were discussed. The results were asfollows. Cetyl trimethyl ammonium bromide could enhance the current response of Pb²⁺and Cd²⁺significantly. Pb²⁺and Cd²⁺showed high peak current on the glassy carbonelectrode modified dithizone in HCl solution （pH1.0）. There were linear relationshipsbetween the concentration of Pb²⁺and Cd²⁺and their peak current. And their linearrelationship were y=-7.743x+2.811（R²=0.995） and y=-0.436x+0.820（R²=0.991）separately. This method could be used for the determination of Pb²⁺and Cd²⁺in waterand beverage.②Molecularly imprinted polymer technology had the efficient recognitionperformance. In this work, a new type of Pb²⁺imprinted adsorbent was prepared bysol-gel approach with Pb²⁺as the template and dithizone as functional monomergrafting onto the silica gel surface. And the adsorption mechanism and adsorptionproperties of the imprinted adsorbent were investigated. The results showed that, theadsorption behavior of Pb²⁺imprinted adsorbent to Pb²⁺was chemisorption; itssaturated adsorption capacity to Pb²⁺rose from0.322mmol/g to0.359mmol/g with theincreasing of ambient temperature from293K to303K; the relative selectivity coefficient of the Pb²⁺imprinted adsorbent to Pb²⁺was250as long as Cd²⁺existed,which indicated that the Pb²⁺imprinted adsorbent has a strong adsorption capacity andselectivity for Pb²⁺. There would be also chromogenic reaction between the imprintedadsorbent and Pb²⁺when the concentration of Pb²⁺was higher than10μmol/L. Resultsof the Pb²⁺imprinted adsorbent used for Pb²⁺in real samples was satisfactory.③The magnetic composition was prepared by dipping method with dithizonegrafting onto the surface of strontium ferrite. The adsorption mechanism and adsorptionproperties of the magnetic complex were studied by infrared spectrometry and staticabsorbing test. The main results were following. The magnetic composition wasprepared by forming hydrogen bonds between strontium ferrite and dithizone, itssaturated adsorption capacity to Pb²⁺and Cd²⁺were0.320mmol/g and0.300mmol/grespectively, and it had high stability.