ZIF-8 metal-organic network/poly(vinyl alcohol) composite for adsorptive removal of various organic dyes

The removal of organic dyes from wastewater is crucial for environmental protection and water treatment. In this study, a ZIF-8/poly(vinyl alcohol) (PVA) composite was prepared for highly efficient dye adsorption using the contra-diffusion method. We investigated the conditions for ZIF-8-PVA to adsorb congo red (CR), including the influences of contact times, initial CR concentrations, pH values, and cyclic use. The results demonstrated that ZIF-8-PVA had a high Brunauer-Emmett-Teller (BET) surface area of 1704.03 m2/g. It exhibited a high removal efficiency of 98.43 % for CR, and its maximum adsorption capacity was 829.39 mg/g. After six cycles of adsorption, the removal efficiency of CR remained over 94.36 %. The removal efficiency of CR under a range of pH from 3 to 10 was consistently over 96.30 %. Moreover, ZIF-8-PVA also displayed adsorption capacity for various cationic and anionic dyes. The adsorption process aligned well with both the Langmuir model and the pseudo-second-order kinetic model. Based on FTIR, XPS, and swelling degree analyses, the adsorption mechanism was elucidated. Due to its universality and reusability, ZIF-8-PVA is suitable for practical application.