Study On Adsorption Characteristics Of Heavy Metals In Wastewater Treated By Modified Chestnut Shell

With the develop of global economy,the demand of water resources is increasing,and the problem of pollution is becoming more serious,especially the heavy metals pollution caused by Indiscriminate discharge is the most serious pollution,so the inevitability of the wastewater produced determines the necessity of wastewater treatment.Currently treating heavy metal by biosorption method is a hot focus of study because it has many advantages such as good adaptability, abundant sources,with good effect for low concentration wastewater etc.Chestnut shell was select as raw material then chosen potassium permanganate and saponification modified Chestnut shells asadsorbent,which had a good performance of adsorption Zn²⁺?Cd²⁺ and Pb²⁺.The experimental studied on the simulated water, analyzed the adsorption mechanism in terms of influential factors,such as initial pH,adsorption equilibrium time, adsorbent quantity, reaction temperature and initial ion concentration etc. As well as adsorption isotherm and kinetics of modified chestnut shell. The experiment result showed:?1?Potassium permanganate and saponification modified Chestnut shells of Zn²⁺? Cd²⁺ and Pb²⁺ adsorption effect is higher than the unmodified Chestnut shells.On even ground, saponification modified Chestnut shells of Zn²⁺ adsorption is best,adsorption rate reached more than 95%, the adsorption quantity was 0.475mg·g-1.Potassium permanganate modification of Cd²⁺ and Pb²⁺ adsorption effect is better, the adsorption rate reached 96.38% and 97.41% respectively, the adsorption quantity were 2.409mg·g-1 and 4.870mg·g-1.?2?PH is one of the important factors in the process of adsorption of heavy metals, when the reaction temperature was 28?,5.0 was the best pH of modified chestnut shells of Zn²⁺?Cd²⁺ and Pb²⁺ adsorption,among the Zn²⁺ adsorption rate reached more than 94.1%, Cd²⁺ reached 96.37% and Pb²⁺ reached more than 97.4%.?3? In solution pH is 5.0 and the reaction temperature was 28 ?,with the dosage of modified chestnut shell cast increase from 0.05 to 0.5g,the heavy metal ions adsorption rate was first increases then decreases, and finally the trend is leveling off, the adsorption quantity are obvious downward trend.The best modified chestnut shell cast was 0.2g?50ml?, Zn²⁺ adsorption rate reached more than 98.2%, Cd²⁺ reached 98.4% and Pb²⁺ reached more than 97.6%.The adsorption quantity was highest when the modified chestnut shell cast was 0.05g, Zn²⁺ reached 0.900mg·g-1, Cd²⁺ reached 4.476 mg·g-1 and Pb²⁺ reached more than 8.866 mg·g-1.?4?With the increase of initial ion concentration, modified chestnut shells of Zn²⁺? Cd²⁺ and Pb²⁺ adsorption rate were decreased and the adsorption quantity were increased. When the Zn²⁺ ion concentration was 0.2mg·L-1,the maximum adsorption rate was 86.94%,the maximum adsorption quantity was 0.710mg·g-1 when the Zn²⁺ ion concentration was 1.8mg·L-1; the concentration of Cd²⁺ ion was lmg·L-1,the maximum adsorption rate was 99.25%,the maximum adsorption quantity was 2.776mg-g-1 when the ion concentration was 6mg-L-1;When the Pb²⁺ ion concentration was 2mg·L-1,the maximum adsorption rate was 95.122%,the maximum adsorption quantity was 4.727mg·g-1 when the ion concentration was 12mg·L-1.?5? With the increase of reaction time, adsorbent for heavy metal ions adsorption quantity were first increased then leveling off. The best adsorption temperature was 28 ?, too high or too low adsorption temperature will cause the adsorption quantity decreased.?6?Adsorption kinetics fitting result of modified chestnut shells, Quasi secondary kinetics equations is fit for modified chestnut shells for fitting of heavy metals adsorbent process,it indicate that the adsorption reaction was given priority to with chemical reaction.Adsorption isothermal curve of modified chestnut shells, Freundlich isothermal adsorption model can better describe the adsorption of Cd²⁺, Pb²⁺ and Zn²⁺ than Langmuir model,this indicate the adsorption reaction was gave priority to with multilayer adsorption, monolayer adsorption is complementary.