| In recent years, The harm events of heavy metals in China become more and more, which seriously impact on people’s life and health, The purpose of this study was to seek low cost and high heavy metal ion adsorbent, and Solve the secondary pollution, high operation cost, large energy consumption in heavy metal waste water treatment and so on. Commonly used low concentration of heavy metal wastewater treatment method have the high cost of running, large investment, complex operation and management of inconvenience and secondary pollution, etc,It is not easy to solve problems such as recycling of wastewater containing heavy metal ions. Using agriculture and forestry waste treatment to the industrial wastewater which contain heavy metal can not only reduce the pollution of the waste water, then reduce the cost, thus speed up the agriculture and forestry waste comprehensive utilization.The chestnut resources are very abundant in our country, at the same time, the chestnut wastes are also increasing, If the chestnut shells are recycled, it will be good use to energy, Section of the sustainable utilization of plant resources and environmental protection.This experimental studied on the chestnut shells adsorption simulated wastewater of Pb2+, Cd2+and Zn2+, and the influence factors in the experiment research, and on the adsorption kinetics and isothermal adsorption has carried on the related research, for chestnut shells in purifying water quality, wastewater treatment, toreduce the cost of water treatment, metal recycling, broadening the scope of use aspect of biological adsorbent provides the basis in theory and reality.The experiment research has the following several aspects(1) In the range of particle size of0.15-3.2mm, Chestnut shells had a small influence on the adsorption of Pb2+, the best adsorption particle size was2mm, the maximum adsorption rate was95.69%; Chestnut shells had a great influence on the adsorption of Cd2+, the best adsorption particle size was0.15mm, the maximum adsorption rate was68.41%; Particle size had obvious influence of chestnut shells adsorption Zn2+,the best adsorption particle size was2mm, the maximum adsorption rate was60.5%.(2) PH of chestnut shells has a great influence of heavy metal ion adsorption, the best PH of Chestnut shells on the adsorption of Pb2+was4-5, the maximum adsorption rate was95.44%; the optimum PH of Chestnut shells on the adsorption of Cd2+was about5, its maximum adsorption rate was85.00%; the optimum PH of Chestnut shells on the adsorption of Zn2+was6, its maximum adsorption rate was86.15%.(3) With the increase of dosage of chestnut shell cast, Pb2+, Cd2+, and Zn2+adsorption rate was first increases then decreases, Chestnut shells dosing quantity was0.2g, Pb2+maximum adsorption rate was97.31%; Chestnut shell dosing quantity was0.4g, Cd2+maximum adsorption rate was96.45%; Chestnut shell dosing quantity was0.3g, Zn2+maximum adsorption rate was87.87%. Chestnut shells dosage among0.025-0.5g, the adsorption of Pb2+from14.27mg/g down to0.84mg/g, The adsorption of Cd2+from4.45mg/g down to0.45mg/g, The adsorption quantity of Zn2+from0.74mg/g down to0.10mg/g.(4) In the10-360min time, the adsorption rate increases with the increase of temperature, When the adsorption time was360min, different temperature on the adsorption of Pb2+was maximum; Within10-300min adsorption time, adsorption rate increased with the increase of temperature increase, When the adsorption time was300min, different temperature on the adsorption of Cd2+and Zn2+was maximum. Adsorption360min under30℃, chestnut shells of Pb2+maximum adsorption rate was99.49%; Adsorption300min under30℃, chestnut shells of Cd2+maximum adsorpt ion rate was83.68%; Adsorption300min under30℃, chestnut shells of Zn2+maximum adsorption rate was85.35%.(5) The Pb2+adsorption rate and adsorption quantity increases with the increase of mass concentration, when the Pb2+initial concentration was12mg/L, the maximum adsorption rate was86.76%, the maximum adsorption capacity is4.75mg/g; The adsorption of Cd2+rate decreases with the increase of the mass concentration, Cd2+Initial concentration was lmg/L, the maximum adsorption rate was98.23%, The adsorption of Cd2+increased with the increase of its concentration increases,Cd2+initial concentration was6mg/L, the maximum adsorption quantity was2.18mg/g; The adsorption of Zn2+rate decreases with the increase of the mass concentration, Zn2+Initial concentration was0.2mg/L, the maximum adsorption rate was75.2%, The adsorption of Zn2+increased with the increase of its concentration increases, Zn2+initial concentration was1.8mg/L, the maximum adsorption quantity was1.03mg/g.(6) In the competitive adsorption,Pb2+adsorption rate and adsorption quantity that increases with the increase of its concentration, The adsorption of Cd2+rate decreases with the increase of mass concentration, the adsorption quantity increases with the increase of mass concentration; The adsorption of Zn2+rate decreases with the increase of mass concentration, the adsorption quantity increases with the increase of mass concentration; Chestnut shells in the competitive adsorption of three kinds of heavy metal ions adsorption choose order is Zn2+>Cd2+>Pb2+, The chestnut shells for the adsorption of Cd2+rate is highest.(7) Quasi secondary kinetics equations suitable for chestnut shells for fitting of heavy metal ions, The correlation coefficient is greater than0.999, Chestnut shell on the adsorption of Pb2+and Cd2+and Zn2+is controlled by the physical and chemical reactions. Factors such as the speed of the generator, the change of temperature will have influence on the rate of adsorption. (8) Langmuir and Freundlich model equation can better fitting chestnut shells of Pb2+Cd2+and Zn2+isothermal adsorption process, The correlation coefficient is1.0000, this Showed that the chestnut shells to the adsorption of Pb2+and Cd2+and Zn2+is complex, there are both the monolayer adsorption and multilayer adsorption, so two adsorption mode coexisting phenomenon can be determined. |
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