Study On The Adsorption Performance Of Dye By Modified Biomass Materials

In our country,dye products are widely used in various industries of production and life,which bring economic benefits to people and produce a large amount of dye wastewater at the same time.Dye wastewater is harmful to human health and the growth of animals and plants because of its complex composition,large chromaticity and difficult degradation.At present,the methods of treating dye wastewater include biological method,chemical method and physical method.Among them,adsorption method in physical method has attracted extensive attention because of its advantages such as simple operation,safety and environmental protection,no secondary pollution,good treatment effect and so on.The common materials used to prepare adsorbents are biomass materials,activated carbon,attapulgite and so on.It has become a hot spot for scholars at home and abroad to find cheap,efficient and environmentally friendly adsorbents.Okara is by-product in the processing of soybean products,and the output is huge.The main component is cellulose,and there is little research on the preparation of adsorbents from which cellulose is extracted.Therefore,okara was used as raw materials to modify and prepare adsorbents in order to further explore the adsorption performance.(1)In this paper,three dyes,methylene blue(MB),neutral red(NR)and malachite green(MG),were selected as adsorbents,and cellulose adsorbent(OA),were prepared by using okara as raw materials.Sodium dodecyl sulfate modified sorbent(SOA),700 o C carbonized okara based biochar(BC-OA)was used to adsorb three kinds of sorbents.(2)The characterization results showed that,for the adsorbents OA and SOA,there were many mesoporous and obvious folds on the surface,and the structure were very fluffy.At the same time,according to the comparison of infrared spectra before and after adsorption,the functional groups of hydroxyl(O-H),carbonyl(C=O)and ether bond(C-O-C)were electrostatically attracted to the dye molecule.For the adsorbent BC-OA,the porous structure of the surface was honeycomb,and at the same time,the characteristic peak of benzene ring or aromatic group appears at the absorption peak of 1560.55 cm-1,which promoted the formation of aromatic groups after high temperature treatment.(3)Single factor experiments included the amount of adsorbents,the adsorption time of p H,the initial concentration of the solution and the concentration of salt ions in the solution.Theobtained optimal p H value of adsorbents OA and SOA was 8.0(the neutral red precipitates under alkaline conditions,so the optimum p H value was 6.0).The optimum adsorbents for dye MB,NR and MG were 0.8 g/L,0.8 g/L and 1.0 g/L,respectively.The equilibrium time was 60 min.According to the designed orthogonal experiment of L9(34),the optimum experimental conditions for adsorption of three dyes by three adsorbents were determined.(4)The experimental results of adsorption of three dyes by three adsorbents were fitted and analyzed by Langmuir model,Freundlich model and Temkin model.The results showed that the Langmuir model was more consistent with the adsorption process of three adsorbents.The maximum adsorption capacity of OA,SOA and BC-OA for MB were 238.10 mg/g,334.83 mg/g and 158.00 mg/g,respectively.The adsorption capacity of the adsorbents for NR were 208.33 mg/g,227.27 mg/g and 212.76 mg/g,respectively.The maximum adsorption capacity of MG were 40.98mg/g,125.00 mg/g and 454.54 mg/g,respectively.The adsorption process of the three adsorbents were well fitted with Temkin,this showed that the model had general applicability.(5)The thermodynamic results showed that the adsorption process of the three adsorbents was spontaneous,among which,the adsorption of three dyes by OA and SOA was exothermic,while the adsorption of three dyes by BC-OA was endothermic.(6)Five cycles of adsorption and desorption of OA,SOA and BC-OA on three adsorbents were carried out by ultrasonic oscillation.According to the experimental data,the regeneration efficiency of the adsorbent decreased gradually,and the adsorption capacity also decreased.(7)The results of adsorption kinetics study show that the pseudo-second order kinetic model can better fit the adsorption process of three adsorbents for dyes,and the correlation coefficient R2 were beyond 0.9957.At the same time,the adsorption rate constants k1 and k2 are all less than 1.It showed that the adsorption reaction rate was very fast.The experimental results were fitted by the intraparticle diffusion model and the external diffusion model.The results showed that the correlation coefficient R2 of the three adsorbents in the external diffusion model were all higher than that of the intraparticle diffusion model.At the same time,the fitting diagram of the external diffusion model did not cross the origin,which indicated that the external diffusion was the main factor controlled the adsorption reaction rate.(8)The adsorption mechanism of three kinds of adsorbents was discussed by the analysis of the results of the adsorption and characterization of the adsorbents.The interaction between the adsorbent OA and the SOA adsorption dye was mainly reflected by the electrostatic attraction and the effect of the adsorbent BC-OA on the dye combined electrostatic attraction with ?-? stacking.The adsorbent material studied in this paper is modified by okara,which is cheap,easy to obtain,friendly to the environment,no secondary pollution,and good adsorption effect.Therefore,the adsorbent prepared in this study has certain application prospects.