| With the rapid acceleration of urbanization and industrialization, the contamination of water environment becomes serious due to the man-made pollution. Thus, the application of environmental-friendly materials in wastewater treatment has received considerable attention in recent years. According to the research on present situation, the products made from chitosan or porous silica materials have been developed to treat wastewater in our study, and the possible mechanisms for the pollutants removal have been proposed. The main original conclusions of this work are drawn.(1) H2O2-induced modification of chitosan was developed to improve the adsorption of dyes onto chitosan. The modified chitosan showed a more ordered structure and a higher hydrophilic character without significant change of functional group on surface, comparing with the untreated chitosan. By the analysis of the hydrophilic character, zeta potential and XPS of untreated and pretreated chitosan, it can be inferred that the enhancement of interaction between the dye and chitosan was attributed to the increase of free hydroxyl and amine groups on the chitosan surface due to the partial removal of amorphous components induced by H2O2. Thus, the adsorption results indicated that the dye removal efficiency improved about 60% after the chitosan pretreated with 200 mM hydrogen peroxide for 2 h.(2) A fast and highly efficient method for the removal of dyes under alkaline conditions using magnetic chitosan-Fe(Ⅲ) hydrogel was proposed. The sorption of dye to chitosan-Fe(Ⅲ) hydrogel was fast (adsorption could reach equilibrium in less than 10 min) in a wide pH range, and fit well to the Langmuir-Freundlich adsorption model with a high maximum adsorption capacity of 294.5 mg/g under pH=12. The results reported herein indicated that magnetic chtisoan-Fe(Ⅲ) with high adsorption efficiency and strong magnetic property is very attractive and implies a potential of practical application for alkaline dyeing effluent treatment.(3) Despite the high adsorption efficiency (maximum adsorption capacity of 173.1 mg/g in 10 min), the significant improvement of Cr(Ⅵ) reduction by chitosan-Fe(Ⅲ) complex compared with normal crosslinked chitoan has been demonstrated. In addition, the structure of chitosan-Fe(Ⅲ) complex and its functional groups concerned with Cr(Ⅵ) detoxification have been characterized by the powerful spectroscopic techniques X-ray absorption fine structure (XAFS) and X-ray photoelectron spectroscopy (XPS). The XPS spectra indicated that the primary alcoholic function on C-6 served as an electron donor during Cr(Ⅵ) reduction and was oxidized to a carbonyl group. A possible process and mechanism for highly efficient detoxification of Cr(Ⅵ) by chitosan-Fe(Ⅲ) complex has been elucidated.(4) A new efficient catalyst, CoTSPc@chitosan, was developed by immobilizing water soluble Cobalt (Ⅱ) tetrasulfophthalocyanine onto adsorbent chitosan microspheres covalently for the heterogeneous catalytic oxidation of C. I. Acid Red 73 with H2O2. The result indicated that the COD removal and discoloration of C. I. Acid Red 73 made 55% and 95% respectively in the presence of CoTSPc@chitosan with H2O2 in 4 hours. In addition, CoTSPc@chitosan-H2O2 system could proceed efficiently in a relatively wide pH range and remain high catalytic activity after 6 reuse cycles. The combination of adsorption process and catalytic oxidation made the CoTSPc@chitosan-H2O2 system achieve a simple, efficiently and environmentally friendly water treatment.(5) A facile and green approach that improves the catalytic lifetime of cobalt tetrasulfophthalocyanine (CoTSPc) for the degradation of dyes is presented. In the catalytic oxidation study, CoTSPc that was immobilized to MCM-41 silica (CoTSPc@MCM-41) prepared at a pH of 12 showed the longest catalytic lifetime. The TOC removal and discoloration of C. I. Acid Red 73 was approximately 60% and 82%, respectively, in the presence of CoTSPc@MCM-41 with H2O2 after three hours. These results indicate that MCM-41, which has a matching size between its mesopores (30 A) and CoTSPc molecules (25 A), can prevent CoTSPc molecules from aggregating and improve its catalytic lifetime.(6) The catalyst Fe2O3-ZSM-5 was perpared to catalyze the conversion of p-chlorophenol (p-CP) to low molecular weight organic acid. The selective conversion was achieved through the adsorption control of p-CP and organic acids on ZSM-5. During the p-CP conversion procedure, the Si/Al ratio of ZSM-5 and the loading of Fe2O3 were two crucial factors which could improve the efficiency of conversion. The highest p-CP conversion efficiency was achieved under the catalysis by Fe2O3-ZSM-5 with the Si/Al ratio of 80 and the Fe2O3 loading of 1.4% or 2.1%. |
PDF Full Text Request