Study Of Preparation Of Chestnut Shell Adsorbent And Its Application

Heavy metal pollution, especially heavy metal pollution in water has become a global issue, with the rapid development of the industrial process. It isDifficult to treat because of its composition and content of pollutants vary greatly. Adsorption of heavy metal treatment process has occupied a pivotal position, is commonly used as pre-treatment and depth of processing methods.The effect of conventional adsorbent although is good but the pretreatment requirements high and the price of raw materials is more expensive, how to develop a cheap and efficient adsorbent is a hot research direction of current environmental workers. Agriculture and forest products are variety in our country. Among the variety agricultural wastes, chestnut shell huge amount, and prices low. Therefore, the preparation of adsorbent treatment used chestnut shell can effectively reduce the production cost. In this study, we prepared efficient water treatment adsorbent with chestnut shells as raw material, to enhance its adsorption properties by chemical modification. Determine the best conditions of preparation and adsorption, by investigating its influence factors in the process of preparation and adsorption of heavy metal ionsThis experiment modified chestnut shell by salicylic acid, to determin the best processing conditions through the single factor experiment and orthogonal optimization. The best processing conditions for modified chestnut shell adsorption of Cr(?) as follows: the concentration of salicylic acid is 0.06 mol/L, mix 30 min, and solid-liquid ratio is 1:10; modified chestnut shell adsorption of Cu(?) as follows: the concentration of salicylic acid 0.14 mol/L, 30 min, reaction time and solid-liquid ratio is 1:15; modified chestnut shell adsorption of Ni(?) as follows: 0.14 mol/L salicylic acid concentration, reaction time for 30 min, material liquid ratio of 1:30. The treated wastewater of Cr(?), Cu(?), Ni(?) can reach discharge standards. The product has been characterized by FT-IR, SEM, EDS, TGA and Zeta potentiometric analysis. Infrared spectrum analysis showed that the surface of modified chestnut shell does not introduce new functional group. combined with the experimental results show that: modified of chestnut shell just to increase the number of phenolic hydroxyl, not changing functional categories; SEM spectrum shows the surface of modified chestnut appeared a lot of cavity structure and morphology changes obviously; EDS test results can be seen that, as a result of salicylic acid react with alcohol hydroxyl groups on the surface of chestnut shell and connected to the surface of chestnut shell, and C, O, Ca content of chestnut shell changed; TGA analysis showed the modification caused the lower thermal stability of modified chestnut shell;Zeta potential analysis showed that after salicylic acid modification the surface potential of chestnut shell increased obviously.Studied the single adsorption process of Cr(?), Cu(?), Ni(?) ion on modified chestnut shell. The results showed that: in dosing quantity is 8 g/L, the initial pH is 4, reaction temperature 25?, the reaction time for 120 min, the removal rate for Cr(?) is 99.9%; in dosing quantity is 10 g/L, the initial pH is 5, reaction temperature 25?, the reaction time for 120 min, the removal rate for Cu(?) is 88.0%; in dosing quantity is 10g/L, the initial pH is 5, reaction temperature 25 ?, the reaction time for 120 min, the removal rate for Ni(?) is 92.3%.Using quasi secondary dynamic equation is a good way to fitting single adsorption process of Cr(?), Cu(?), Ni(?) on the modified chestnut shell, the results showed that: the secondary dynamic linear equation is t/qt=0.0414t+0.5245?t/qt=0.053t+0.3411 ? t/qt=0.0515t+0.2422 respectively. The correlation coefficient of dynamic equation for a single of adsorption process Cr(?), Cu(?), Ni(?) on modified chestnut shell is 0.9981, 0.9943, 0.9976, respectively.Compared with a single adsorption process of the three ions, the removal rates of mixed adsorption are lower, the reduction of Cr(?) is the minimum, and Cu(?) is the largest, the relations of the three kinds of ions in the mixed adsorption belong to antagonism. Competitive adsorption sequence is: Cr(?) > Ni(?) > Cu(?). In mixed adsorption process, the secondary dynamic linear equation is t/qt= 0.0595t+0.2845?t/qt= 0.0831t+0.4741?t/qt= 0.0985t+0.5414 respectively. the quasi linear correlation coefficient of Cr(?), Ni(?), Cu(?) adsorped on modified chestnut shell is 0.9991, 0.9963, 0.9967 respectively. Explain the mechanism of the three kinds of heavy metalsn on the modified chestnut shell with diffusion model. The results show that the adsorption process of three kinds of heavy metal on the modified chestnut shell are not caused by exposure to a diffusion model, namely the adsorption process is not only control by internal diffusion.According to the thermodynamics research results, regardless of adsorption alone or mixed, the adsorption process of Cr(?) on chestnut shell is the endothermic reaction, the adsorption process of Cu(?), Ni(?) on chestnut shell is the exothermic reaction.