| With the rapid development of urbanization and industrialization,a large amount of domestic sewage and industrial wastewater containing heavy metal ions are discharged into rivers and seas,and groundwater is one of the most toxic heavy metal ions.Excessive copper ions not only affect the growth of animals and plants.And it has certain harm to the health of the human body.Biochar adsorbents prepared from biomass such as agricultural and forestry wastes are a promising alternative to heavy metal treatments,while reducing manufacturing and operating costs.The walnut shell of agricultural and forestry waste has large specific surface area ion exchange property,physical adsorption and chemical adsorption can be carried out without processing to prepare activated carbon,and the original walnut shell can be further modified to enhance the ability to adsorb Cu2+.Modification of the original walnut shell by plasma modification can improve the chemical adsorption capacity of the walnut shell to copper ions,which is beneficial to the removal of heavy metal copper ions in water.In this paper,the low-temperature plasma modification of the original walnut shell under the condition of ultra-fine water mist was carried out,and the copper ion adsorption of the walnut shell before and after modification was studied.The modification time was studied(5,7.5,10,12.5,15,30 min),different ultra-fine water mist flow rate(0.5,1.5,3 g/min),different adsorption contact time(10,20,30,40,60,90,120 min)modified walnut shell to copper ion The adsorption capacity,in addition,also studied the adsorption capacity of copper ions after pH and walnut shell adsorption-desorption cycle regeneration.The Langmuir isotherm model was selected to analyze the adsorption isotherm model of copper ions on the original walnut shell and modified walnut shell.The data of the adsorption of copper ions in the original walnut shell and the modified walnut shell accorded with the Langmuir isotherm model(the value of R2 is 0.927-0.994).In the range),it indicates that the adsorption of copper ions on the surface of the original walnut shell and the modified walnut shell is a uniform single-layer adsorption process.The kinetics of copper ions on the original walnut shell and the modified walnut shell were analyzed,and three kinetic models were established:Pseudo-first-order model and Pseudo-second-order model.And the Weber-Morris model,the results show that the quasi-secondary model can fully describe the adsorption process,which shows that the adsorption of copper ions on the original walnut shell and modified walnut shell is mainly chemical adsorption.SEM(scanning electron microscopy)analysis of the original walnut shell and modified walnut shell showed that the original walnut shell surface was rough and the structure was small;the surface of the modified walnut shell had obvious porous structure and was covered by small particles.The XPS(X-ray photoelectron spectroscopy)analysis of the original walnut shell and the modified walnut shell showed that the C and O elements were the main elements,and the O element of the modified walnut shell was higher than the O element of the original walnut shell,and the elements.The results obtained from the analysis are consistent.XPS analysis showed that the modified walnut shell significantly increased the COOH functional group compared with the original walnut shell.The COOH functional group on the modified walnut shell was significantly reduced after the adsorption of copper ions,which proved that the COOH functional group is a favorable copper ion adsorption site.Through the experimental and mechanism analysis of this study,it can be concluded that the COOH functional group was successfully added to the walnut shell modification,and because the COOH functional group is an effective copper ion adsorption group,the ultra-fine water mist low temperature plasma modified walnut shell added COOH.Effectively improve the adsorption capacity of copper ions. |
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