Adsorption Of Heavy Metal In The Preparation Of Hydrogels And Its Application In Metallurgical Sludge

Industrial development not only promotes social and technological progress,but also brings a variety of environmental pollution problems,especially in heavy metal pollution.As a by-product in papermaking industry,lignosulfonate is a kind of renewable resource with abundant source and low price.The adsorption of heavy metal ions in metallurgical sludge by sodium lignosulfonate has the practical significance of waste disposal,resource reuse and environmental protection.In this paper,two kinds of sodium lignosulfonate adsorbent were synthesized and characterized.In addition,a molecular model for the adsorption of lead ions by sodium lignosulfonate was established,and the adsorption mechanism lead ion by sodium lignosulfonate was discussed.The main contents and results are as follows:1.Sodium lignosulfonate was modified with hydrogen peroxide as oxidant and sodium sulfite as sulfonating agent.The adsorption properties of modified sodium lignosulfonate were studied under different factors(eg initial concentration,pH,temperature,adsorption time).The results show that the adsorption capacity of lead and cadmium by modified sodium lignosulfonate is affected by the initial concentration,pH and adsorption time of heavy metal,but it is not affected by temperature.The kinetic study shows that the static adsorption process of lead and cadmium by modified sodium lignosulfonate satisfies the quasi-first order kinetic model,and the adsorption process belongs to Langmuir isothermal adsorption model.2.A chitosan-lignosulfonate hydrogel was prepared andused to adsorb lead ions.The result of SEMshows that there are different sizes of voids on the hydrogel surface.the result of nitrogen adsorption method shows that the specific surface area of the hydrogel is0.2678m~2/g and the pore volume is 0.00014cm~3/g.The effects of initial concentration,pH value,adsorption temperature and time on the adsorption of leadwith sodium lignosulfonate hydrogel were studied.The results show that the adsorption capacity of sodium lignosulfonate to lead ion increases with the increase of pH value.When the pH is equal to 5,the adsorption capacity of lead ions reaches the maximum.However,the effect of adsorption temperature is not obvious.The adsorption capacity increases with the initial concentration increasewhen the initial concentration is under 400 mg/L.The kinetic study shows that the static adsorption process of sodium lignosulfonate on lead ions satisfies the quasi-second order kinetic model,and the adsorption process is agreed with Langmuir isothermal adsorption model.3.The mechanism of the adsorption of lead by sodium lignosulfonate has been studied by density functional theory on the molecular scale.The model of sodium lignosulfonate was established,and the structure of sodium lignosulfonate and the lead complex were optimized by density functional method at B3LYP/6-311G(d,p)level.Based on the analysis of surface electrostatic potential,it was found that the sulfonic acid group,the methoxygroup and the hydroxyl group on the benzene ring were active sites for adsorption in the sodium lignosulfonate model.However,the results of charge decomposition analysis,the molecular orbital analysis and the interaction energy show that were the sulfonic acid group has better adsorption property of lead;thistheory results consistent with the results of adsorption experiments that the sulfonated lignin has better adsorption ability of lead than the oxided lignin.The result indicates that during the lignin adsorption of lead ions,the increase of sulfonic acid groups will be more conducive to adsorption.