Study On The Adsorption Of Pollutants From The Aqueous Solution By Modified Chitosan And Wheat Straw

Chitosan and wheat straw can be used as adsorbent to remove pollutants from water. Adsorbent capacity can be enhanced through modification. In this study, Ch-Fe was prepared by modification of chitosan using FeCl3·6H2O and glutaraldehyde. The ethylenediamine(EDA) was introduced into wheat straw surface through grafting reaction, while epichlorohydrin(ECH) was grafting reagent. Then xanthan acidification straw(CS2-WS.) was prepared by chemically reaction between carbon disulfide and ethylenediamine grafted straw.The absorbents were characterized by isoelectric point, X-ray diffraction, X-ray fluorescence, fourier transform infrared spectroscopy, elemental analysis, scanning electron microscopy. When Ch-Fe compared with crosslinked chitosan(CCTS), Ch-Fe behaved more stable in adsorption capability toward 2,4-dichlorophenoxyacetic acid(2,4-D) at various pH values. The equilibrium adsorption quantity of CS2-WS and NWS were 3.11 mg·g-1 and 44.4 mg·g-1 respectively, at the same adsorption condition. A new adsorbent was prepared by CS2-WS adsorption of Cu2+ and try to use it to absorb Congo red(CR), a typical azo dye.Adsorption time, initial concentration, the pH value, coexisting ions, temperature were selected to study their effects on the adsorption quantity in static adsorption. The presence of coexisting ions is negative to adsorb 2,4-D, but it is in favor of Cu2+ and congo red adsorption. It was found that the pH value was a major factor for the three adsorption process. Both Koble-Corrigan and Langmuir models can describe the isotherms of three adsorption systems. This showed that the adsorption process was based on monolayer adsorption. The kinetic process of 2,4-D on Ch-Fe can be well described by pseudo-first-order-kinetic model, pseudo-second-order kinetic model and Elovich model. While pseudo-second order kinetic model and Elovich model were better to fit the adsorption process of Cu2+ on CS2-WS and CR on CS2-WS-Cu2+. The thermodynamics results demonstrated that the adsorption of 2,4-D on Ch-Fe was a spontaneous, exothermic, entropy decreased process; the adsorption of Cu2+ on CS2-WS and the process of congo red on CS2-WS-Cu2+ were spontaneous, endothermic, entropy increased process.The height of column, flow rate and initial concentration were designed in column adsorption experiments. Three classical models, Thomas model, Clark model and Yan model were used to fit adsorption data and the result showed that Thomas model was most appropriate model to describe the adsorption process Cu2+ on CS2-WS, while Yan model was best to describe the second adsorption process.0.1 mol·L-1 HCl were best eluent for desorbing 2,4-D and Cu2+, While 75% ethanol was best choice for desorbing CR. The result of regeneration test indicated that the adsorbent Ch-Fe was the best, CS2-WS-Cu2+ was the second and the CS2-WS was worst in regeneration capacity.