Synthesis And Application Of Novel Magnetic Hypercrosslinked Resin Modified With Amino Group

With the development of economy, wastewater from chemical industry has caused serious pollution to the environment. Due to its complex compositions and large volume, chemical wastewater severely threatens ecological safety and human health. Currently, chemical wastewater is mainly disposed by pretreatment technologies tandem secondary biochemical treatment. However, the secondary effluent still contains a lot of unbiodegradable organics and hazardous components, which demands advanced treatment. Adsorption technology with activated carbon is a common and economic advanced treatment method, whereas the limitations including low mechanical strength and difficulty to regeneration hinders its application. In comparison, resin adsorbents have been widely used in water treatment owing to the large adsorption capacity, high mechanical strength, and strong regeneration capability. Therein, a hypercrosslinked resin modified with amino group has been developed. The bifunctional adsorbent eliminates hydrophilic compounds by ion exchange and removes hydrophobic organic pollutants by adsorption. Therefore, it has been applied for the disposal and reclamation of concentrated and unbiodegradable chemical wastewater. Nonetheless, this resin is generally employed in fixed bed, which demands large investment and high operational cost. Besides, the treatment volume is too low to meet the requirements of practical applications with large water volume.Recently, Orica company in Australia has developed a magnetic ion exchange resin, MIEX(?), which possesses various advantages including fast adsorption kinetics, ease of separation, and facile operation. MIEX(?) could be applied in completely-mixed reactors, conquering the limitations of low water volume and high energy cost of fixed bed. MIEX(?) has been employed in drinking water and municipal wastewater treatment. Another magnetic ion exchange resin, NDMP, is also developed by Chinese researchers. However, these magnetic resins eliminate pollutants by ion exchange, which exhibit low capability for hydrophobic compounds. Few studies reported magnetic resin adsorbents with high specific surface area for the removal of pollutants by synergistic ion exchange and adsorption. Based on the above background, this thesis focused on the preparation and application of a novel magnetic hypercrosslinked resin modified with amino group. The main content and conclusions are as follows.(1) A magnetic hypercrosslinked resin modified with amino group was successfully prepared by suspension polymerization. After the screening of monomer species and ratios and the optimization of preparation methods, the optimized sorbent possessed high specific surface area (>550 m2/g) and large exchange capacity (0.98～1.49 mmol/g). The particle size ranged from 80 to 250 μm, and the saturation magnetization was 1.60～1.79 emu/g.(2) Two representative pollutants in chemical wastewater, 4-nitrotoluene-2-sulfonic acid (NTS) and 2-nitrotoluene (o-MNT), were selected as adsorbates to investigate the adsorption performance of a series of novel adsorbents. It was observed that the adsorbed amount of ionic pollutant NTS was positively proportional to the ion exchange capacity of resins, whereas the adsorbed amount of molecular pollutant o-MNT was influenced by the specific area, pore volume and porous structure. The prepared adsorbent exhibited high removal efficiency for both pollutants. The adsorption kinetics were remarkably superior to that of NDA-88. The adsorption of o-MNT was primarily physisorption, while chemisorption dominated and physisorption contributed to the adsorption of NTS. The adsorption of NTS was not significantly influenced by NaCl, but the adsorbed amount of o-MNT improved with increasing NaC1 concentrations. After 10 adsorption-desorption cycles, the adsorption capacity scarcely decreased, demonstrating excellent regeneration property.(3) The prepared novel adsorbents were applied to the advanced treatment of chemical wastewater. Among the synthesized adsorbents, GMA30-1 with the specific area of 718 m2/g, exchange capacity of 1.49 mmol/g and average pore size of 4.17 nm exhibited the best adsorption capability. The optimal resin amount was 3 wt% of the treated water amount, and the optimized desorption agent was the mixed solution of ethanol and 6% NaOH solution at the ratio of 4:6. After 8 repeated cycles, the novel adsorbent still maintained high treatment efficiency. The CODcr value of the effluent complied with the GB18918-2002 1A discharge standard.