Studies On The Behavior And Mechanism Of Adsorption Of Instant Tea Dregs On Heavy Metal Ion In Wastewater

Almost every country is confronted with environmental problem of wastewater containing heavy metal ion, in varying degrees. The heavy metal ion exists in every part of the whole aquatic after entering it, and impairs the structure and function of ecosystem. To develop a simple, economical and effective method to treat heavy metal ion in wastewater, by adsorption experiment, the characteristics and mechanism of adsorption to cadmium, lead and chromium (VI) ion on instant tea dregs were studied. The mainly results as follows:1. It illuminated that the instant tea dregs had fine adsorption effect on cadmium, lead and chromium (VI) ion of middle or low concentration by experiment, and the adsorption effect was better than actived carbon..2. The orthogonal experimental results indicated: the optimum condition of adsorption to cadmium ion was that the pH was 2, the temperature was 60℃, and soaking time was 3 hour; to lead ion was that the pH was 2, the temperature was 30℃, and soaking time was 5 hour; to chromium (VI) ion was that the pH was 4, the temperature was 80℃, and soaking time was 5 hour.3. The two models for Langmuir and Freundlich were used to fit the experimental data of cadmium, lead and chromium (VI) ion adsorbed by instant tea dregs, and it showed that adsorption laws of cadmium and lead ion obeyed the Langmuir equation, but chromium (VI) ion obeyed the Freundlish equation; the results indicated that the dynamical data fitted better with the second-order kinetic model than the first-order kinetic model.4. The adsorption rate of cadmium and lead ion was increasing as the granularity reduce of instant tea dregs, but the granularity had minimal impact on adsorption rate of chromium ion. The best way of adsorption to cadmium and lead ion was mixing way, the second one was surging way, the last was static way; the adsorption rate of the two kinds of ion was increasing as the velocity of mixing and surging speeding up, but the way of adsorption to chromium (VI) ion had little effect on adsorption.5. By studying on desorption, physics and chemistry character of tea and detection by Scanning Electron Microscope, Brunauer Emmett Teller, Infrared Spectrometer, it showed that the reaction process should occur chemical adsorption and physisorption to cadmium and lead ion, whereas the main adsorption was chemical adsorption to chromium (VI) ion.The instant tea dregs had fine adsorption effect on heavy metal ion of actual water sample, which is significance for supplying new material of treatment of wastewater, reducing dregs amount of production procedure of instant tea, increasing the added value of producing, and it provides theoretical basis and scientific foundation for adsorption of instant tea dregs on heavy metal ion in wastewater.