Fabrication and characterization of sodium alginate and polyamidoamine dendrimer bio-nanocomposites modified by in-situ synthesis of ZIF-67 and study on highly selective adsorption performance.

To solve the problems of low adsorption capacity, low selectivity and difficulty in solid-liquid separation that exist in the application of MOFs, innovative bio-nanocomposites were successfully prepared combining MOFs with natural polymer sodium alginate (SA) and polyamidoamine dendrimer (PAMAM) through hybridization and in-situ synthesis strategies. Adsorption kinetics curves of cationic dye methylene blue (MB) and anionic dye methyl orange (MO) were well fitted by pseudo second-order kinetic model. Adsorption isotherm curves for MB and MO could be best fitted by Langmuir and Dubinin-Radushkevich isotherm model, respectively. Thermodynamic studies had shown that adsorption process of MB was spontaneous and advantageous, and attributed to physical adsorption. SA/PAMAM-0.2@ZIF-67-1 showed the highest adsorption capacity (up to 1422.20 mg·g-1) for MB and relatively low adsorption capacity (only 49.78 mg·g-1) for MO at 35 °C. The presence of ions was beneficial for the removal of organic dyes. When the value of pH was 10, adsorption selectivity of SA/PAMAM-0.2@ZIF-67-1 was optimal, reaching up to 378.66. After 4 consecutive cycles, regeneration efficiency still reached over 80 %. Adsorption driving forces were mainly electrostatic interactions, hydrogen bondings, π-π conjugations, coordination effect and van der Waals forces. The research results could provide theoretical reference and technical support for the design, fabrication and application of innovative and high adsorption selectivity bio-nanocomposites.