Preparation Of Chitosan Derivatives-Bentonite Composites And Study On Its Simultaneous Adsorption Of Heavy Metals And Dyes

Nowadays,the rapid development of Chinese industry has brought about numerous wastewater containing dyes and heavy metals,which poses a serious threat to mankind and environment.When the wastewater containing dyes and heavy metals was treated,adsorption method was widely used due to these advantages such as simple operation,high efficiency,etc.In this paper,two highly efficient,non-toxic and easily renewable adsorbents were prepared by using chitosan derivatives to modify bentonite?BT?and applied in the removal of dyes and heavy metals from simulative wastewater.Firstly,chitosan was modified to obtain chitosan quaternary ammonium salt?QCS?and carboxymethyl chitosan?CCS?.Then,the two chitosan derivatives were applied to the modification of bentonite,and the resultants were obtained as QCS/BT and CCS/BT composites.The structure of the adsorbents was investigated by FTIR and XRD techniques.The effect of the preparation conditions of adsorbents on the adsorption of dyes and heavy metals were discussed,including the ratio of chitosan derivatives to bentonite,types of cross-linking agent,the cross-linking time and concentration.Also,the factors affecting the adsorption of dyes and heavy metals such as adsorbent dosage,initial solution concentration,adsorption time and temperature,etc were also investigated.Besides,the adsorption characteristics and mechanisms of heavy metals and dyes were also.The conclusions were obtained as follows:In this study,the simultaneous removal of Cr?VI?and Amido Black 10B?AB10B?by QCS/BT composite was investigated by a batch method.In the preparation of QCS/BT composite,the 1.2 ratio of QCS to BT was adopted and 2.5%glutaraldehyde was applied for the crosslinking reaction for 15 hours.0.03 g of adsorbent dosage and 540 min of contact time were applicable.The adsorption equilibrium data were described by both isotherm and dynamics models.The results shown that the adsorption of Cr?VI?and amino black 10B were correlated with the Langmuir and the pseudo-second order models.The maximum adsorption capacity of Cr?VI?and AB10B was 63.78 and 925.9 mg/g at 318 K,respectively.The thermodynamic model indicated that adsorption was a spontaneous process.Adsorption mechanism included the existence of chelating and electrostatic interaction between Cr?VI?and QCS/BT composite,and hydrogen bonding and electrostatic interaction between AB10B and QCS/BT composite.In addition,the obvious competitive adsorption existed between Cr?VI?and AB10B.In order to further explore the simultaneous adsorption of heavy metals and dyes from aqueous solutions,the simultaneous adsorption of Fuchsin Acid and Cu²⁺onto CCS/BT composite was also investigated.In the preparation of CCS/BT composite,glutaraldehyde was chosen as the cross-linking agent and the crosslinking reaction occurred for 5 h.The adsorption equilibrium data had a good agreement with the Langmuir isotherm and the pseudo-second order models.The maximum adsorption capacity was calculated as 253.17mg/g for Fuchsin Acid and 81.43 mg/g for Cu²⁺at 298 K under natural pH.The main adsorption mechanisms included chelating and hydrogen bonding effect.The CCS/BT adsorbent was effectively regenerated with NaOH.