Adsorption Of Cu(?) And Cr(?) In Solution By Complex Modified Chitosan

Heavy metal pollution in water is one of the severe tests that human beings are facing.Adsorption method is widely used as an efficient method to remove heavy metals from water.Chitosan?CS?has the characteristics of low cost and environmental friendliness,and can be used as an ideal heavy metal adsorbent,which has received extensive attention in recent years.In this study,chitosan?CS?was modified by ferric chloride hexahydrate?FeCl3·6H2O?and sodium dodecyl sulfonate?SDS?.Preparation of trivalent iron modified chitosan?CS-Fe?,sodium dodecyl sulfate modified chitosan?CS-SDS?and trivalent iron,sodium dodecyl sulfate composite modified chitosan?CS-Fe-SDS?.Taking Cu???and Cr???as the target substance,the influencing factors such as the dosage of the adsorbent,the pH of the solution,the adsorption time and the initial adsorption concentration were studied experimentally.At the same time,the modified adsorbent was characterized by FIRT,SEM and XRD to explore the modification mechanism and adsorption mechanism.The main results are as follows:?1?The CS-Fe,CS-SDS and CS-Fe-SDS modified adsorbent materials were prepared by homogeneous method.The adsorption of Cu???and Cr???by these three modified materials was greatly affected by pH.In the experimental range,the optimum adsorption pH of the materials for the two heavy metals was 5.5 and 3.0,respectively.?2?The adsorption rates of CS-Fe,CS-SDS and CS-Fe-SDS for the same heavy metal are different.For Cu???,the three adsorbent materials reached adsorption equilibrium at 90,30and 60 min.For Cr???,the three adsorbent materials reached adsorption equilibrium at 35,50 and 120 min.?3?Through the pseudo-first and second-order kinetic models,the Langmuir and Freundlich models fit the experimental data to obtain the following conclusions:The adsorption of Cu???by three materials is mainly chemical adsorption,the adsorption of Cr???is the result of a combination of chemical adsorption and physical adsorption.The results show that the adsorption of Cu???by materials is dominated by single-layer adsorption,and the adsorption of Cr???has a single-layer adsorption process and a multi-layer adsorption process.The maximum adsorption capacities of CS-Fe for Cu???and Cr???were 79.72 and169.28 mg/g,respectively.The maximum adsorption capacities of CS-SDS for Cu???and Cr???were 215.83 and 61.40 mg/g respectively;the maximum adsorption capacities of CS-Fe-SDS for Cu???and Cr???were 173.34 and 131.91 mg/g,respectively.?4?The adsorption effects of three materials on Cu???and Cr???were compared and analyzed.It is considered that CS-Fe-SDS has good adsorption capacity,and it is used as the research object for subsequent interference ion experiment and characterization mechanism analysis.When there are interfering ions in the adsorption process,the presence of common cations does not have a great influence on the adsorption of Cu???by CS-Fe-SDS;while the anion does not have a significant effect on the adsorption of Cr???by CS-Fe-SDS in addition to CO₃^2-.The adsorption of Cu???and Cr???mixed solution by CS-Fe-SDS showed that the presence of Cu???and Cr???promoted the adsorption of another ion.In the experimental range,the Cu???can increase the adsorption capacity of Cr???by 42%,and the Cr???can increase the adsorption capacity of Cu???by 70%.?5?FIRT,XRD and SEM characterization were performed on the CS-Fe-SDS materials:the results show that SDS and Fe?III?have been successfully loaded on CS.The modified material has a low crystallinity and exhibits a polymerized,irregular,amorphous state.