The Preparation Of Chitosan-stabilized FeS Magnetic Composites And Its Application For Chromium Removal

Chitosan-stabilized FeS magnetic（MC-FeS）composites were successfully prepared to address the easily oxidization of FeS and enhance Cr（Ⅵ）removal from water.The main results of this study are as follow:（1）The results of influencing factors showed that under acidic condition,the adsorption of Cr（Ⅵ）by MC-FeS had better effect and the optimum pH was 3.With the increase of adsorbent dosage,the Cr（Ⅵ）removal efficiency increased and the adsorption capacity decreased.Anion coexisting in water such as Cl^-and NO₃^-can inhibit the removal of Cr（Ⅵ）,but the common existence of dissolved organic matter exerted a negligible effffect on Cr（Ⅵ）removal.The MC-FeS composites enhanced the Cr（Ⅵ）removal capacity as compared to bare FeS.（2）The result of kinetic experiments showed that the adsorption process of Cr（Ⅵ）by MC-FeS followed pseudo-secondary kinetics model and the R² was 0.999,the adsorption process was controlled by chemical adsorption.Adsorption isotherm experimental results demonstrated that the adsorption process followed the Redlich-Peterson adsorption isotherm model which indicated that it was a hybrid chemical reaction-sorption process.（3）SEM analysis showed that The fresh MC-FeS particles showed a clearly angular and small lamellar structure with multiple holes,but after reaction the edges of the MC-FeS particles tended to be smooth,and the holes were not as clear as before.FT-IR analysis showed that the vibration bands at 1145 and 1112 cm^-1 shifted to 1070 and 1037 cm^-1,respectively,after the reaction.Moreover,the intensity of the characteristic peaks at 1562 and1411 cm^-1 decreased or even disappeared.These peaks shifting and the change in the intensity of the characteristic peaks may have been because the amino and hydroxyl groups are the major functional groups involved in Cr（Ⅵ）removal.Further investigation using X-ray photoelectron spectroscopy showed that FeOOH,S₈,Cr₂O₃,Cr₂S₃,and a Fe（III）-Cr（III）complex were apparently introduced by Cr（Ⅵ）,Fe（II）,and S（-II）,respectively.In addition,the MC-FeS composite presented high stability against aging and performed well in a long-term reaction system and typical natural water environment.The effective performance of MC-FeS composites shows their great potential in wastewater remediation contaminated by heavy metals.