Preparation Of Chitosan-derived Adsorption Materials And Their Adsorption To Dye Wastewater

Dye is one of the common consensus pollutants in wastewater due to their strong toxicity,non-biodegradability and accumulation in plants,animals and human beings.Because of the increasing diversity of industrial products,the component of dye wastewater turns increasing complicated and the treatment of which becomes an extremely difficult task.It can severely affect the aquatic life and the food web even in a low concentration by weakening the penetration of light in water and inhibiting the photosynthesis capacity of aquatic organisms.It also can cause health problems such as difficulties in breathing,diarrhea,vomiting and nausea to humans and animals.It is significant and urgent to remove dye from wastewater.Chitosan?CTS?is a biological polysaccharide and widely existed in nature.It has desirable properties like hydrophilicity,low cost,biocompatible and biodegradable.It contains amino and hydroxyl groups that can serve as adsorptive sites for dyes.Therefore,chitosan-based derivatives have great research value in wastewater treatment.In this study,chitosan was used as substrate and eight kinds of adsorbent materials with different structures and different properties were prepared by design modification.The products were characterized by using FTIR,TGA,SEM,XPS and XRD.The cationic dye methylene blue?MB?,anion dye reactive brilliant red?RBR?and reactive yellow?RY?were chosen as the model target of adsorption.The adsorption capacities of dyes were obtained by UV-Vis.The experimental result had reference value and guidance significance to the development of green adsorption material,proving its great potential for removal of dye from wastewater.Firstly,twokindsofpolyaminatedchitosancrosslinkedmicrospheres,triethylenetetraamine aminated microspheres TETA-CTSms and polyethyleneimine aminated microspheres PEI-CTSms were prepared by using microphase emulsion crosslinking technology.The characterization results showed that the content of amine of the polyaminated microspheres was greatly improved.The results of adsorption experiments showed that the adsorption properties of microspheres TETA-CTSms and PEI-CTSms for MB were normal,while the adsorption properties for RBR and RY were better.The adsorption capacity of TETA-CTSms to RBR reached 265.16mg/g in 3 h,and the adsorption process conformed to the pseudo-second-order model.The adsorption of RY by TETA-CTSms and PEI-CTSms reached 546.69mg/g and 234.48mg/g in 3h,and the adsorption process conformed to the pseudo-second-order model.During the adsorption of RY,the adsorption capacity of the two polyaminated microspheres increased with the decrease of pH.With the increasing concentration of NaCl solution,the adsorption of RBR on TETA-CTSms increased gradually,while the adsorption capacity of RY decreased.The adsorption capacity of PEI-CTSms for RY increased with increasing the concentration of NaCl in solution.The isothermal adsorption of RBR by PEI-CTSms was in accordance with the Langmuir and Temkin model,reconfirming that the adsorption process included both physical adsorption and chemical adsorption.The isothermal adsorption of RY on TETA-CTSms was in accordance with the Langmuir model,belonging to monolayer adsorption.In addition,the isothermal adsorption of these two polyaminated microspheres was spontaneous endothermic reaction.To improve the recycling performance of the adsorbent material,the magnetic ferriferrous oxide particles were blended with the aminated chitosan solution.The magnetic triethylenetetraamine-amine microspheres TETA-MCTSms were prepared by using the microphase emulsion crosslinking technology.In addition,the graft polymerization of MAA on chitosan microspheres was carried out by initiating of the surface-initiating system of–NH₂/S₂O₈^2-,forming carboxylated magnetic microspheres MCTSms-PMAA.The characterization results showed the surface of TETA-MCTSms was successfully polyaminated,and the MCTSms-PMAA surface was successfully carboxylated.In the adsorption experiments,MCTSms-PMAA exhibited better adsorptive properties for the cationic dye MB,and the adsorption process conformed to the pseudo-first kinetic model.The adsorption capacity of MB increased with the increasing of pH and the concentration of NaCl.The adsorption of MB showed a good fit using the Langmuir isotherm,with the largest correlation coefficient R².At the same time,TETA-MCTSms exhibited good adsorptive properties for RBR.The adsorption process followed pseudo-first-order model and the adsorption capacity reached 197.91mg/g in 3h.The adsorption capacity decreased with the increasing of p H,and increased with the increasing concentration of NaCl in the solution.The adsorption process of TETA-MCTSms to RBR was a spontaneous exothermic reaction,and the Langmuir isotherm model had the highest correlation coefficient.In this chapter,considering that a large amount of organic solvents was used in the microphase emulsion crosslinking method and the subsequent product cleaning was also tedious,two kinds of adsorbents,polyethylenimine-chitosan particles PEI-CCTS and triethylenetetraamine-chitosan particles TETA-CCTS were prepared by one-step in the solution.Chemical modification of the chitosan with amine increased the adsorption.A very high adsorption capacity of 383.63mg/g was observed for RBR.The adsorption kinetics and isotherms of RBR on TETA-CCTS followed pseudo-second-order model and the Langmuir model.It showed that the adsorption of RBR by TETA-CCTS was uniform adsorption on the surface,and the theoretical adsorption amount at 20°C was as high as 1428.04mg/g.The chitosan-acetic acid solution was used as a matrix,and acrylic acid and acrylamide monomers were added,and then the initiator ammonium persulfate was added to form an–NH₂/S₂O₈^2-redox initiation system in the solution,and the graft copolymerization of acrylic acid and acrylamide was caused on the chitosan molecular chain,preparing the grafted material PAA-AM/CTShb.The adsorption capacity of PAA-AM/CTShb for MB increased with the increasing of pH.In addition,the adsorption capacity of PAA-AM/CTShb for RBR decreased with the increasing of pH.The adsorption capacity of of PAA-AM/CTShb for RBR and MB increased with the concentration of NaCl.The adsorption kinetics of MB on PAA-AM/CTShb was more consistent with the pseudo-second-order model.The adsorption isotherms of MB on PAA-AM/CTShb followed the Langmuir model.In recent years,composites prepared by coordination of transition metals and macromolecules have been widely studied and used to remove contaminants in wastewater.The chitosan grafting material PAA-AM/CTShb was first fully chelated with Fe?III?,and then was cross-linked and fixed with glutaraldehyde,obtaining the Fe?III?-chitosan composite material Fe-c-CTS.The adsorption results showed that the adsorption kinetics of RBR on Fe-c-CTS was more consistent with the pseudo-first-order kinetics model,and the adsorption capacity of RBR decreased with the increasing of pH.The isothermal adsorption process of RBR by Fe-c-CTS followed Langmuir isotherm and the correlation coefficient R² was the largest.