The Application Of Ti-pillared Montmorillonite On Arsenic Removal In Pu’er Tea

In this paper, Ti-pillared montmorillonite composite of high selectivity for the removal of arsenic ions in tea was prepared through hydrolysis method. The application of Ti-pillared montmorillonite in removing arsenic was conducted, with the exploration of the operating parameter of instrumentation, the method of detection and the criterion of detection. Through detecting and analyzing the loss of tea polyphenol during the adsorption, a technology of removing trace-amount arsenic ion in tea was formed preliminarily.Firstly, through analyzing the test results of ICPMS and AFS, we explored the operating parameter of instrumentation, the method of detection and the criterion of detection, and determined the convenient, propagable and accurate detection method. Meanwhile, we optimized the operating conditions of AFS and investigated the influence of hydrochloric acid, potassium borohydride, potassium hydroxide, thiourea, lamp current, flow of carrier gas ect.. The best test conditions were 2% hydrochloric acid as the medium, 1% potassium borohydride as reducing agent, 0.2% potassium hydroxide as stabilizer, 1% thiourea as pre-reducing agent, negative high voltage 270 V, lamp current 80 A, the flow of carrier gas 700 mL/min, the flow of aux gas 200 m L/min. The experiments of RSD and accuracy of sample testing were explored. The results shown that the RSD of tea powder detected by parallel three times was less than 5% and recovery was between 93.35% and 106.86%. The data were reliable and satisfactory.Secondly, the best reaction conditions of adsorption were determined through exploring the consumption of adsorption material, adsorption time and reaction temperature. The test results show that: with the increasing of Ti-pillared montmorillo-nite and reaction time, the content of arsenic in tea decreased. But when the reaction time increased to 4 h, the residual amount of arsenic in tea powder didn’t risen. The adsorption effect changed little in the adsorption reaction temperature between 20 to 50℃ and the content of arsenic in tea decreased from 22.0652 μg/L to 15.4721 μg/L, which indicated that Ti-pillared montmorillonite had excellent adsorption efficiency in removal of arsenic in tea.Finally, the content of tea polyphenols were detected before and after the adsorption of Ti-pillared montmorillonite. The initial and final content of tea polyphenols was 9.68% and 8.80%, respectively, and the loss rate was 9.09%. The test results showed that Ti-pillared montmorillonite could adsorb arsenic in tea effectively, not on causing great damage to tea polyphenols, which consisted with the relevant provision.