Application Of Magnetic Nanoparticles To Remove Organic Dye Pollutants

The textile industry, one of the traditional pillar industries of China, was an industry consuming a large quantity of water, containing high content of organic matter and causing high-pollution. The wastewater discharged from the textile industry, including weaving wastewater, printing wastewater, mercerizing wastewater, bleaching effluent, dyeing wastewater and finishing wastewater, was considered as a serious threat to ecosystem. It is estimated that the daily discharged volume from printing and dyeing industry was 3000 to 4000 kt, and it is one of the large sewage industry in recent years. With the industrial development of dye industry and printing processing technology, the stability of dyes was greatly improved, as well as the continuous application of new additives, a large number of hazardous pollutants were dischaged into the printing and dyeing wastewater, which has greatly increased the difficulty of the wastewater treatment. Therefore, the development of cost-effective processing technology for printing and dyeing wastewater treatment has attracted increasing attention in today’s environmental protection industry, which can play a vital role in protecting the environment to maintain ecological balance. This study used different materials and different methods to remove several types of dyes including methylene blue (MB) and rhodamine B (RhB) which cause water environment pollution. By examining the impact of various factors on the dye removl, the optimum experimental conditions were choosed to achieve the purpose of efficiently removing harmful pollutants. The main results are as follows:(1) Prussian blue (PB) modified y-Fe2O3 magnetic nanoparticles (PBMNPs) were successfully synthesized and characterized by FT-IR, XRD, TEM and used to remove organic pollutants from aqueous solution using MB as model compound. The experimental results showed that the target compound could be removed efficiently from solution over a wide pH range from 3 to 10 in the presence of PBMNPs as peroxidase-like catalyst and H2O2 as oxidant. Under optimal conditions, MB could be removed completely after 120 min of reaction at 298 K, the chemical oxygen demand (COD) removal efficiency and the total organic carbon (TOC) abatement efficiency were 53.6% and 35%, respectively. Furthermore, the PBMNPs catalysts showed the high magnetization, temperature tolerance, long-term storage and operational stability, and could be readily separated from solution by applying an external magnetic field. Finally, a possible reaction mechanism for MB degradation was also discussed.(2) CoFe2O4-AC magnetic nanocomposites were synthesized and characterized by XRD and TGA. The magnetic nanocomposites were used as adsorbent for the removal of MB and RhB dye from water. The effect of solution pH, adsorption isotherms and kinetics were investagated in detail. The results indicated that CoFe2O4-AC magnetic nanocomposites could effectively remove MB and RhB. The adsorption of MB and RhB onto CoFe2O4-AC magnetic nanocomposites both fitted well with the Langmuir and Freundlich model. The adsorption capacity of MB (107.04 mg/g) were about two double of that of RhB (58.51 mg/g). Moreover, the adsorption kinetics of MB and RhB were found to follow pseudo-second-order kinetic model. CoFe2O4-AC magnetic nanocomposites could be reused and easy to be separated under the external magnetic field. It was found that the as-prepared magnetic nanocomposites could be used as a promising and effective adsorbent for the removal of MB and RhB from water.(3) Fe3O4-MWCNTs magnetic nanocomposites were synthesized and characterized by XRD, FT-IR and TGA. The magnetic nanocomposites were used to remove organic pollutants from aqueous solution using MB as a model target. The experimental results showed that the removal efficiency of Fe3O4-MWCNTs magnetic nanocomposites for MB was greater than that of Fe3O4 and MWCNTs alone. Moreover, the effect of H2O2 concentration, Fe3O4-MWCNTs magnetic nanocomposites concentration, pH, temperature and TOC changes in the reaction process were investagated in detail. Under optimal conditions,97.41% of MB could be removed after 12 h of reaction at 298 K. Finally, the recycling experiment of Fe3O4-MWCNTs magnetic nanocomposites was studied. The results demonstrated that the removal efficiency of MB was kept 100% after the first two-recycle run while the removal efficiency decreased to 79.96% after the recycle number increased to five. This showed that the Fe3O4-MWCNTs magnetic nanocomposites may become a promising catalyst in environmental wastewater treatment.