Study On The Adsorption Of Anionic Dye (Amido Black 10B) By Cation-Modified Chitosan/Bentonite Composite

With the development of economy, synthetic dyes are used in many industries such as textile industry and paper industry. Dye wastewater emissions have great harm to the environment and human beings, so the problem of Amido Black 10 B pollution that need to be solved. At present, the treatment of dye wastewater by adsorption method has many advantages and broad market prospect. Chitosan, as the second largest renewable resource in nature, has features like no toxicity, biocompatibility and adsorption, which is widely used in the treatment of dye wastewater. However, the instability of Chitosan making its application restricted, so it was often combined with bentonite and other minerals, which could not only reduce the cost of adsorbent, but also improve the adsorption efficiency. Therefore,in this study, the cationic groups was introduced on chitosan and bentonite to prepare available adsorbents for Amido Black 10B(AB10B) removal, named Zr(IV) surface-immobilized cross-linked chitosan/bentonite composite(Zr-CCB) and the cross-linked quaternized chitosan/bentonite composite(CQCB). The preparation, physicochemical characteristics,adsorption properties and mechanism of AB10 B adsorbents were discussed. The structure and morphology of the adsorbents were characterized by FTIR, XRD, SEM and EDAX techniques. The adsorption of an anionic dye, Amido Black 10 B, from aqueous solution by Zr-CCB and CQCB composite was investigated as a function of adsorbent dosage, initial concentration, pH value, adsorption time, temperature etc. The conclusions were as follows:Zr-CCB was synthesized by immersing cross-linked chitosan/bentonite composite(CCB)in zirconium oxychloride solution. In the process of Zr-CCB preparation, 0.2 g ZrOCl2·8H2O was added into reaction system, and the immersing temperature was 25℃with the immersing time 20 h. The removal of Amido Black 10 B increased with an increase in loading amount of Zr(IV) and adsorbent dosage, but decreased with an increase in pH. The adsorption of Amido Black 10 B onto Zr-CCB was favored at lower pH values and higher temperatures. The Langmuir isotherm model fitted well with the equilibrium adsorption isotherm data and the maximum monolayer adsorption capacity was 418.4 mg/g at natural pH(9) value and 298 K.The kinetic data by Zr-CCB were correlated with the pseudo-second order kinetic model.Thermodynamic parameters indicated that the nature of Amido Black 10 B adsorption was spontaneous and endothermic. The possible mechanisms controlling Amido Black 10 B adsorption included hydrogen bonding and electrostatic interactions.In order to improve adsorption capacity, CQCB was prepared by membrane-forming and cross-linking methods, the dosing mass ratio of the chitosan quaternary ammonium salt and bentonite was 4:5, and the chosen cross-linking agent was epichlorohydrin with cross-linking time 20 h. Batch mode was adapted for the adsorption studies. The equilibrium data and kinetic data were well described by the Langmuir isotherm and the pseudo-second-order kinetic model, respectively. The maximum monolayer adsorption capacity was obtained at990.1 mg/g at 298 K and natural pH(9) in terms of the Langmuir model. The thermodynamic results indicated that the adsorption of Amido Black 10 B by the CQCB was spontaneous and endothermic in nature. The high adsorption capacity was attributed to the strong electrostatic interaction as well as hydrogen bonding.