Research On Adsorption Of Lead Ions And Methylene Blue Using Alkaline-modified Tea

In this research,waste tea from processing factory was modified with alkaline activation.The result showed that under the condition of 0.2mol/L sodium hydroxide and 24-hour modification,the adsorbent effect of the modified tea is best.Compared with unmodified tea,the removal and adsorption capa city of heavy metal lead ions by the best preparation of modified tea increased by 47.44% and 39.3956mg/g.The removal and adsorption capacity of methylene blue increased by 32.76% and 52.6402mg/g.The colour of modified tea which was soft and bulking turn ed from light green to dark green.Through the determination of specific surface area analyzer,the specific surface area of modified tea was 4.007m2/g which was higher than 1.677m2/g of unmodified tea.The scanning electron microscope analysis showed that alkalinemodified tea had more microporous structure.FT-IR analysis showed that each group content of modified tea increased,including that absorption peak enhanced and the absorption peak of saturated hydrocarbon C-H,amine C-N and halogenated hydrocarbon C-X moved.Use static adsorption experiment to investigate the impact of main factors on the removal of lead ions by modified tea.It was found that adsorption process was greatly influenced by PH value.The removal rate increased with the increase of p H value and the adsorption effect was best when p H=5.As adsorbent quantity increased,the removal rate of lead ions increased,adsorption quantity decreased,and the best dosing quantity is 1.2g/L.The adsorption of lead ions by alkali ne-modified tea was a rapid process and got the adsorption equilibrium after 3h.The coexisting ions had a great influence to the removal rate of lead ions and the order of their interference was: Ca2+> Mg2+> K+> Na+.The removal rate of lead ions reduced when the concentration of coexisting ions improved.The adsorption of lead ions by modifi ed tea was consistent with pseudo second order model and Langmuir adsorption isotherm model.The reaction △S=37.1585J/mol·K,△H=6.1448 k J/mol,△G<0 indicated that the whole adsorption process was spontaneous endothermic reaction.Electron microscopy scanning combining spectral component analysis showed that after the adsorption of Pb2+,alkaline-modified tea got less microporous structure and had a layer of relatively dense plaques on the surface originating from the adsorption of Pb2+.FT-IR analysis showed that the active groups of modified tea for the adsorption of Pb2+ were hydroxyl-OH and halogenated hydrocarbon C-X.Use static adsorption experiment to investigate the impact of main factors on the removal of methylene blue by alkaline-modified tea.It was found that adsorption process was hardly influenced by PH value.As adsorbent quantity increased,the removal rate of methylene blue increased,adsorption quantity decreased,and the best dosing quantity is 0.6g/L.The adsorpt ion of methylene blue by alkaline-modified tea was a rapid process and got the adsorption equilibrium after 3h.The coexisting ions had a great influence on the removal rate of methylene blue and the order of their interference was: Ca2+> Mg2+> K+> Na+.The removal rate of methylene blue reduced when the concentration of coexisting ions improved.The adsorption of methylene blue by modified tea was consistent with pseudo second order model and Langmuir adsorption isotherm model.The reaction △ S=37.1585J/mol·K,△H=6.1448 k J/mol,△ G<0 indicated that the whole adsorption process was spontaneous endothermic reaction.Electron microscopy scanning combining spectral component analysis showed that after the adsorption of methylene blue,alkali ne-modified tea got less microporous structure and had a layer of relatively dense plaques on the surface originating from the adsorption of methylene blue.FT-IR analysis showed that the active group of modified tea for the adsorption of methylene blue were hydroxyl-OH and halogenated hydrocarbon C-X.