Facile preparation of metal organic framework material decorated chitosan composite to efficiently rid hazardous dye...

The design and preparation of adsorbents are crucial in the field of wastewater treatment. The composite adsorbents with chitosan (CTS) and metal organic framework (MOF) were fabricated to enhance the diffusion degree of MOF and acid stability of CTS by heating reflux method and effect of ratio of CTS, Cu²⁺ and 2-aminoterephthalic acid of the composite adsorbents on adsorption was investigated. The diffusion degree of MOF on the composite adsorbent (CTS-MOF) was enhanced on the basis of FESEM images. The acid instability of CTS on the CTS-MOF was improved as CTS can partly dissolve in solution with pH lower than 4.0, while the composite was stable. The composite material was used to remove anionic dye methyl orange (MO) from contaminated aquatic environments. The adsorption kinetics showed that the adsorption capacities of CTS-MOF, CTS and MOF for MO with concentration of 200 mg/L were 135.49, 34.84 and 58.95 mg/g, respectively, and the adsorption capacity of CTS-MOF increased to 3.89 and 2.30 times, accordingly, compared to that of CTS and the MOF, due to synergetic effect of CTS and MOF. The adsorption process of CTS-MOF followed pseudo-second-order kinetic model and Langmuir model. In addition, the adsorption was endothermic. For CTS-MOF, the solution pH exhibited slightly small fluctuation on MO adsorption. The presence of NaCl exhibited positive effect for MO adsorption onto the MOF while negative effect for MO onto CTS-MOF, and the influence on the CTS-MOF was much less than that onto the MOF, indicating the salt tolerance of CTS-MOF was better. Adsorption mechanism was analyzed by the FTIR spectra before and after adsorption and quantum chemical calculation by means of independent gradient model based on Hirshfeld partition (IGMH) analysis. And IGMH analysis showed the relative magnitude of coordination effect, hydrogen bonding and π-π stacking involved in the adsorption process. This study provided a valuable method to design and prepare adsorbents with high adsorption efficiencies for organic dyes from aqueous solution.