Preparation And Adsorption Performance Of Graphene Oxide Based Composites For Removal Of Heavy Metal And Dye From Aqueous Solution

Currently, the increasing emissions of sewage and industrial waste water containing heavy metal ions and organic pollutions are strongly toxic, component complex and difficult to biological degradation, which caused serious threathens for people health and living circumstances. Adsorption, due to its low cost, simple operation and good adsorbent effect advantages, is considered one of the most effective methods of waste treatment for heavy metal ions and dye. Graphene oxide as a new nano-materials, equipped with larger surface area and lots of oxygen-containing functional groups in its structure. These unique properties make GO showing a strong advantage on novel nano-composites preparation.Based on the unique properties of GO, this paper design and synthesis of a series of GO composite adsorbents which have the characteristics of quick absorption rates, large adsorption capacity, easy to separate, repeatable, inexpensive and efficient, environmental friendly. In addition, by means of the scanning electron microscopy, energy dispersive spectroscopy, FT-IR and x-ray diffraction, the physical and chemical properties of the prepared new adsorbent materials were characterized. Static adsorption experiments were carried out to study the effect of different factors on the adsorption of pollutants by adsorption material. The equilibrium data are fitted with Isothermal and thermodynamics models, and the adsorption process and rate-limiting step is disCussed. Factors and their interactions on adsorption behavior were evaluated by u sing RSM. The adsorption mechanisms were disCussed by using x-ray photoelectron spectroscopy in the moleCular level. Column adsorption studied and the inlet velocity and initial pollutant concentration on the effect of adsorption properties. The breakthrough Curves were analyzed using dynamic models, which provide a theoretical basis for the practical application of adsorbent. The main achievements of this paper are as follows:(1) Using the solution blending method, magnetic Fe3O4@GO/KMnO4 material was prepared for Cu2+ removal in aqueous. Fe3O4@GO/KMnO4 was characterized, and batch adsorption experiments were carried out to investigate Cu2+ removal performance by Fe3O4@GO/KMnO4. Effect of Ionic strength on the Cu2+ absorption is weak. With a variety of adsorption model to fit the data, results of adsorption equilibrium data is found more in line with the Langmuir model for spontaneous endothermic reactions and adsorption. Adsorption kinetics studies show that Cu2+ follows a pseudo-second order rate model of adsorption, which indicated that adsorption processes involving physical adsorption and chemical adsorption. Using response surface method, Fe3O4@GO/KMnO4 adsorption Cu2+ quadratic regression models and associated statistical parameters show that this model is highly notable, and could be a good simulation of Cu2+ removal with the effect factors between each other. The desorption efficiency and reusable capacity were investigated by using various desorbents with 3 Adsorption-desorption cycles. In addition, in the presence of an external magnetic field, Fe3O4@GO/KMnO4 can be achieved separation and recovery.(2) Using covalent modification method,-SH groups was grafted on graphene oxide nanosheets and prepared GO-SH nano-materials. GO-SH was characterized by means of FTIR, XPS, and EDS methods and the performance of Cu2+ and dye MB removal was studied with static experiments. The results indicated that the adding of-SH strongly enhanced the adsorption velocity and the equilibrium was reached about 20 min. Using the isothermal model to fit the experimental data, discovering that Langmuir isotherm model can fit experimental data very well. Adsorption kinetics results showed that adsorption behavior follows a pseudo-second order rate model. Thermodynamic study showed that the adsorption was spontaneous reactions and endothermic, elevating temperature conducive to the absorption reaction. RSM was used to establish Cu2+ and MB absorption quadratic regression models, and statistical parameters showed that this model is highly significant, which could be a good simulation the relationship of Cu2+ and MB removal between the removal and influence factors. Desorption experiments showed that after 3 adsorption-desorption cycles, Cu2+ and MB adsorption rate maintained the initial adsorption rate of 80%.(3) By using silane coupling agent KH-550,-NH2 modification of GO-N was prepared. Experimental study on the static adsorption showed that at pH 6.0, the equilibrium sorption capacity of Cu2+ reached up to 102.72 mg/g by 0.05 g of GO-N, which showed a better performance than others. The equilibrium adsorption of MB was 462.63 mg/g by 0.01 g of GO-N. The data for absorption of Cu2+ and MB in accordance with Langmuir isotherm models, and the calCulated isolation factor values of RL was also very low. GO-N adsorption kinetics of pseudo-second order rate model can be used to explain mechanism, which mainly involves external diffusion, adsorption and chemical reaction, and so on. Thermodynamics research results showed that Cu2+ and MB adsorption are spontaneous endothermic reactions. Finally, after 3 adsorption-desorption cycles, Cu2+ and MB Removal rate remained the initial adsorption rate of 80% or so, showing that GO-N could be reused.(4) On the basis of the first two chapters, GO-SH and GO-N were embedded in polyvinyl alcohol (PVA), respectively. CaCO3 was as cell opener and boric acid was used as the cross linking agent, PVA/GO-SH and PVA/GO-N was prepared with large bore multiple balls. The adsoption performances of Cu2+ and Pb2+ were studied with static and column adsorption experiments. Cu2+ and Pb2+ adsorption is the most responsive of Langmuir isotherm model. Dynamic model analysis showed that the adsorption rate for Cu2+ was significantly faster than Pb2+. Adsorptions of the two metal ions are all in line with second-order dynamic equations that are dominated by chemical adsorption. XPS analysis showed that the adsorptions of Cu2+and Pb2+ were depend on -SH?-NH2?-COOH group complexes on PVA/Engineered GO or Ion exchange reactions. Column adsorption experiment showed that PVA/Engineered GO have high adsorption efficiency characteristics when influent concentrations of metal ions and flow rate were at lower level. After 5 adsorption-desorption cycles, PVA/Engineered GO remains good ball shape and corruption does not occur, which had a better reuable capacity.(5) By loading the-NH2 modification mesoporous molecular sieves NH2-SBA-15 onto GO, GO/SBA-15 composite adsorbent was prepared. The adsorption capacity was studied using static adsorption experiments. Langmuir, Freundlich, D-R isotherms, pseudo first-order kinetics, pseudo second order kinetics and particle diffusion model were used to investigated the adsorption processes and rate limiting step. Cu2+ and MB adsorption response surface methodology models were established, and these models have a higher significance, indicating they could be a good simulation of removal rate with the interrelationship between factors. Using 0.2 mol/L HCl as desorption agent, recycling experiment showed that after 3 adsorption-desorption cycles, Cu2+ and MB removal rate remained beyond 80%.