A novel silica-reinforced P(AM/AMPS/SA/TM-SiO2) microspheres for selective adsorption of methylene blue from aqueous solution

The development of adsorption materials with large adsorption capacity, high selectivity and strong regeneration ability is of great significance for the treatment of dye wastewater. With the aim of obtaining a microsphere with stable structure, large adsorption capacity and rich negative charge for selective adsorption of methylene blue (MB) and other cationic dyes from aqueous solution, a novel silica-reinforced P(AM/AMPS/SA/TM-SiO2) microspheres were synthesized from acrylamide (AM), 2-acrylamido-1-methyl-1-propane sulfonic acid (AMPS), sodium alginate (SA) and trimethoxy(vinyl)silane modified silica (TM-SiO2) through microemulsion polymerization method. The structural properties of the microspheres were analyzed by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), and dynamic light scattering (DLS). The influences of TM-SiO2 content on particle size distribution, swelling property, and mechanical stability of the microspheres were thoroughly investigated. The results revealed that TM-SiO2 could effectively adjust the particle size distribution range, reduce the swelling degree, and improve the mechanical stability of the microspheres. The effects of temperature, contact time and initial concentration of MB on the adsorption capacity of the microspheres were systematically inquired. The adsorption capacity of P(AM/AMPS/SA/TM-SiO2) microspheres for MB was 362.52 mg/g at 25℃, while that of P(AM/AMPS/SA) microspheres was 307.17 mg/g. Furthermore, P (AM/AMPS/SA/TM-SiO2) nanocomposite microspheres still maintained a complete shape and high adsorption capacity after five adsorption–desorption cycles. The pseudo-second-order kinetic model and Langmuir model were adopted to describe the adsorption process of MB on the microspheres. Moreover, the intermolecular interaction between the microspheres and MB were explored by quantum chemical (QC) calculations. A possible adsorption mechanism was proposed.