| With speed development of dyeing,textiles,leather,paper,and other chemical industries,increasing amount of dye wastewater containing refractory organic dyes are discharged,dyeing wastewater has large chroma,high chemical oxygen demand,high content of organic pollutants,large alkali,and complex water quality.Adsorption process is a simple,effective and low-cost way to remove dyeing wastewater.Therefore,it has created an urgent demand for effective adsorbents with high adsorption capacity and rapid adsorption rate.In this paper,ZnMgAl-LDHs was prepared by co-precipitation method and was modified by dielectric barrier discharge non-thermal plasma,doping soluble starch and intercalated flocculant to improved the adsorption performance of hydrotalcite on dyeing wastewater.The ZnMgAl-LDHs after modified was characterized by XRD,BET,SEM,EDS and FT-IR.The changes of structure and properties of ZnMgAl-LDHs with different modification methods and different modification conditions were analyzed.Adsorption kinetics and adsorption isotherms of ZnMgAl-LDHs adsorbed on methyl orange were studied to analyze the adsorption process of hydrotalcite on methyl orange.Finally,the reusability of modified hydrotalcite was explored.The dielectric barrier discharge non-thermal plasma was used to modify ZnMgAl-LDHs and plasma modification can significantly improve the adsorption properties of ZnMgAl-LDHs.After plasma modification,the average size of the samples particles is smaller,the dispersibility of the crystal grains was better,and the hydrotalcite crystallinity was higher.The adsorption efficiency of samples calcined at 450°C for 5h after plasma modification for 30 min is the highest.The experimental results of the adsorption of methyl orange on the samples accorded with the Pseudo-second-order adsorption kinetics model.The equilibrium data for the adsorption of methyl orange on adsorbents could be well fitted by the Langmuir equation,and the saturated adsorption capacity can reach 1327mg/g.After 5 times regeneration treatments,the samples still have good adsorption properties to methyl orange,indicating that the plasma-modified hydrotalcite has good reusability.ZnMgAl-LDHs were prepared by co-precipitation method and modified with starch to transform the structure for the adsorption property improvement.After the doped soluble starch,the sample had a higher crystallinity,the specific surface area was increased,and the pore volume and the number of pores were increased.The adsorption properties of the doped soluble starch ZnMgAl-LDHs samples after roasting were improved compared to the undoped soluble starch,and the adsorption of methyl orange by the doped soluble starch ZnMgAl-LDHs was carried out when the molar ratio of soluble starch/aluminum ions is 1:16(ie,0.01 mol,1.7115g),the adsorption efficiency was best.The adsorption kinetics of the soluble doped soluble starch ZnMgAl-LDHs adsorbing methyl orange was consistent with the Pseudo-second-order.Adsorption isotherm experimental results can be well fitted to the Langmuir equation.The saturated adsorption capacity of the adsorbent capacity was reached 1555 mg/g.Co-precipitation method,calcination reduction method and ion exchange method were used to prepare ZnMgAl-LDHs intercalated with anion polyacrylamids,cation polyacrylamide and nonionic polyacrylamids three kind of flocculant.From the experimental results,when the mass ratio of polyacrylamide/aluminum is 1:100(0.01g),the ZnMgAl-LDHs intercalated cationic polyacrylamids prepared by co-precipitation method has the best adsorption effect on methyl orange.The results of kinetic experiments show that the adsorption process of hydrotalcite on intercalated polyacrylamid for methyl orange meets the Pseudo-second-order adsorption kinetics model.The adsorption isotherm can be well fitted by the Langmuir equation.The saturated adsorption capacity reached 1251mg/g,and the polyacrylamids intercalated hydrotalcite had good adsorption performance.Dielectric barrier discharge non-thermal plasma,doping soluble starch and intercalated flocculant all can improved the adsorption performance of ZnMgAl-LDHs on methyl orange.By changing the modification conditions,the controlled synthesis of ZnMgAl-LDHs with high adsorption performance to methyl orange was realized.Among these three different modification methods,the dielectric barrier discharge plasma has the advantages of simpleness and quickness,and does not pollute the environment;the hydrotalcite prepared by the modified starch-doped modification method has the best adsorption performance for methyl orange;the intercalated polyacrylamids hydrotalcite has certain potential in the application of actual dye wastewater. |
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