Study On Adsorption Of Dye From Sewage By Modified Bean Dregs

Dyeing wastewater may cause heavy pollution to the water environment with direct discharge, due to the high colority complicated water quality and high content of organic substance.Dyeing wastewater contain chromogenic group,such as-N=N-、-N=O, and polar group,such as-SO3Na、-OH、-NH2.Most of its components contain aromatic hydrocarbons and heterocyclic, these organic pollutants are more difficult to degrade, resulting dyeing wastewater has become an important source of pollution of the major waters. Meanwhile dye wastewater caused some stress to the environment. At present, many methods have been used to deal with such wastewater, such as activated sludge, coagulation, chemical oxidation, Fenton reagent, etc. However, due to the characteristics of the dye, these conventional treatment methods are limited. To a variety of dyes, adsorption method can play a effectively complementary role. Therefore, in recent years, adsorption method of dye wastewater has caused widespread concern.Bean dregs is a byproduct of processing of soy products, At present,bean dregs are except for used to feed, but has not been effectively utilized. Bean dregs contain a lot of cellulose. The reports about cellulose adsorb dye are very common, but the research about bean dregs adsorption of dye is less. Therefore, the study adopted the bean dregs as adsorbent. Modified bean dregs in view of the different properties of acid dyes and basic dyes, to improve its ability to dye adsorption. According to the static, dynamic adsorption and regeneration experiment, and studied the structural change of natural bean dregs and modified bean dregs, providing the reference data for further study on the bean dregs of dye wastewater treatment and the engineering application. The main contents and results are following:(1) The physical and chemical characteristic of natural bean dreg and modified bean dreg were examined by XRD, FT-IR、SEM. The results showed that the changes of physical and chemical characteristics of modified bean dreg. The result of SEM showed that the surface of two kinds of modified bean dregs was more crapy and fluffy than that of natural bean dregs, and the specific surface area area becomes larger. This kind of structure is more advantageous to the adsorption; The FT-IR Spectrum of cationic bean dreg showed that the main structure of modified bean dreg was not altered, but some of the associated functional groups had been modified. The strengthen of a conspicuous peak at1380cm-1in RWS FT-IR, which was associated with tertiary amino group. So the modification process occurred the amination reaction; The FT-IR Spectrum of anionic bean dreg showed that the appearance of conspicuous peaks at1420cm-1、1160cm-1, which was associated with-O-C=S. Showed that CS2with bean dreg successfully occurred the etiolation reaction, and generated xanthic acid ester; XRD analysis showed that the crystall degree of cellulose was not altered after cationic modification; Anionic modified generated xanthate magnesium salt, lead to changes in cellulose crystal.(2) It was founded the suitable adsorption conditions by single factor experiment and orthogonal experiment. The best condition of cationic bean dregs adsorbing acid magenta:pH was7, the temperature was30℃, the absorbent quality was0.6g/L, the dye initial concentration was50mg/L, the adsorption time was4.5h, the adsorbent particle size was less than60mesh. Under this condition, the removal rate of acid fuchsin reached99%.The best condition of anionic bean dregs adsorbing fuchsine:the pH was7, the temperature was35℃, the absorbent quality was0.5g/L, the dye initial concentration was10mg/L, the adsorption time was1h, the adsorbent particle size selected20-60mesh. Under this condition, the removal rate of fuchsin reached99%; The best condition of natural bean dregs adsorbing fuchsine:the pH was7, the temperature was15℃, the absorbent quality was1g/L, the dye initial concentration was15mg/L, the adsorption time was2h, the adsorbent particle size selected20-60mesh.Under this condition, the removal rate of fuchsin reached93%.The adsorption effect of natural bean dregs was worse than anionic bean dregs.(3) The process that cationic bean dregs adsorbed acid fuchsin fitted the Langmuir isotherm((r=0.999, p<0.01). The adsorption process fit the theory of monolayer adsorption. As the temperature increases, the maximum adsorption capacity increased by217.39mg/g and303.03mg/g. The process that anionic bean dregs adsorbed fuchsine fitted the Freundlich isotherm and Tempkin isotherm, the maximum adsorption capacity got to148.68mg/g, and it was4.17times higher than natural bean dregs.(4) The secondary dynamics can describe the adsorption of acid fuchsin on cationic bean dregs better. Calculated by the secondary kinetic rate constants acquire Ea=36.27kJ/mol, and it indicated that the adsorption process existed the active chemical adsorption. The process that anionic bean dregs and natural bean dregs adsorbed fuchsin fitted the the secondary dynamics and Elovich equation, it indicated that chemical adsorption was the the important steps, and the ion exchange played a great role in the whole adsorption process.(5) The process that cationic bean dregs adsorbed acid fuchsin was endothermic, spontaneously and in the adsorption process, there are physical adsorption and chemical adsorption. The process that anionic bean dregs adsorbed fuchsin was endothermic, spontaneously and in the adsorption process, there are mainly chemical adsorption; The process that natural bean dregs adsorbed fuchsin was exothermic, spontaneously and in the adsorption process, there are mainly physical adsorption.(6) The result of dynamic adsorption test showed Thomas model and Yoon-Nelson model can describe the dynamics adsorption of acid fuchsin on cationic bean dregs better. Dynamic adsorption ability of anionic bean dregs were stronger than that of natural bean dregs under the condition of different column height, different flow rate and different initial concentration, and the penetration time and saturate time of anionic bean dregs were both longer than that of natural bean dregs. Thomas model can describe the dynamics adsorption of fuchsin on anionic bean dregs better.(7) Using NaOH as desorption agent, both in the static adsorption and dynamic adsorption, the effect of the desorption cationic bean dregs adsorbed acid fuchsin adsorption is good, can be used repeatedly. Using NaOH as desorption agent, the effect of regeneration on the anionic bean dregs is better, and it is superior to the natural bean dregs.