Preparation Of Graphene Oxide And Its Composite Microspheres And Adsorption Performance Research

Natural polymer materials have attracted researchers'attention in terms of adsorption performance due to their biodegradability,biocompatibility and reproducibility.Compared with traditional adsorbent materials,graphene oxide?GO?has a large specific surface area and rich oxygen-containing functional groups?such as hydroxyl,carboxyl,epoxy,etc.?,which can interact with precious metal ions through chelation and electrostatic forces.The combination makes graphene oxide have better adsorption performance.At the same time,chitosan?CS?itself carries a large number of amino and hydroxyl groups and can be used as an adsorption site for metal ions.Therefore,the above two excellent adsorbents are combined to synthesize a novel composite microsphere adsorbent to enhance the adsorption capacity of precious metal ions.Based on this,we did the following research:The first part uses the modified Hummers method as the synthesis method.Graphite powder is oxidized and reduced by oxidant to obtain graphite oxide,and then dispersed by ultrasound to obtain graphene oxide.Through Fourier transform infrared spectroscopy?FT-IR?and scanning electron microscopy?SEM?and other test methods for structural characterization and material analysis of GO,at the same time study GO adsorption performance,mainly discusses the solution p H,adsorption time,initial concentration of The effect of the adsorption performance of Au???on precious metal ions,as well as the adsorption isotherms and adsorption kinetics of GO adsorption of precious metal ions in aqueous solution were fitted and discussed,and the mechanism of action was analyzed.The results of the study indicate that GO can adsorb 303.030 mg/g of Au???at a p H of 3.0.R²is greater than 0.99 in the adsorption isotherm fitting of Au???by adsorbent GO,which is consistent with the Langmuir isotherm adsorption model;in the adsorption kinetics,the adsorption fitting of Au???on GO follows a pseudo-second-order kinetic model.The second part is based on GO and CS,using glutaraldehyde as the cross-linking agent,and a series of new composite microsphere materials with different ratios are synthesized by the emulsification method,which are labeled CSGO₅,CSGO₁₀and CSGO₁₅,respectively.At the same time,the same method was used to synthesize GCCS microspheres without GO to compare the adsorption performance experiments.Mainly discuss the effect of solution p H,adsorption time,initial concentration,amount of adsorbent,temperature on the adsorption of precious metal Au???,and conduct a two-component selective experiment to explore the effect of CSGO₅microspheres on precious metal Au???under the interference of other ions and the cycle life of CSGO₅microspheres is proved by the adsorption-desorption cycle experiment.The adsorption isotherms,adsorption kinetics and adsorption thermodynamic behavior of precious metal Au???in the aqueous solution of composite microspheres were fitted,analyzed and discussed.The results show that when the p H value is 3.0,the adsorption capacity of the adsorbent for the precious metal Au???reaches the maximum and the adsorption performance is the best.The maximum adsorption capacity of the adsorbent for Au???is:CSGO₅>GCCS>CSGO₁₀>CSGO₁₅>GO,compared with other adsorbents,containing 5wt%graphene oxide chitosan microspheres?CSGO₅?to Au???Has the largest adsorption capacity,and its maximum adsorption capacity for Au???is 751.879 mg/g.In the adsorption isotherm,the fitting of the adsorption isotherms of Au???by each adsorbent fits well with Langmuir isotherm adsorption.In the adsorption kinetics,the fitting kinetics of Au???fits the pseudo-secondary kinetic model.The calculation of Gibbs energy?G^?,enthalpy change?H^?,entropy change?S^?and other thermodynamic parameters shows that the adsorption of Au???on CSGO₅microspheres is spontaneous,endothermic and feasible.The results of adsorption-desorption cycle experiments show that CSGO₅microspheres can be reused,and after four cycles of use,the adsorption capacity of Au???by CSGO₅microspheres has not changed significantly,and the adsorption rate can still reach 98%.In addition,in the two-component selection experiment,the CSGO₅microspheres can recover the precious metal Au???well.The CSGO₅composite microspheres have a good identification and selection performance for Au???,and the selectivity coefficient relative to the base metal is very high.Therefore,graphene oxide/chitosan composite microspheres are a potential promising adsorbent.