Advancing wastewater treatment and metal recovery: Aminated ZIF-8 composite cellulose aerogel as an innovative biomass adsorbent for enhanced molybdenum ion adsorption

Biomass adsorbents possess significant potential for both metal recovery from industrial leaching solutions and wastewater treatment. However, standalone biomass materials suffer from the drawback of low adsorption capacity. In this study, by the combination of metal–organic frameworks (MOFs) with organic biomaterials, a novel aerogel of aminated ZIF-8 composite cellulose (CPEZN) was developed for molybdenum ions adsorption, and the incorporation of aminated ZIF-8 improved the availability of reactive groups. The unique aerogel structure effectively prevented the accumulation of MOFs, thereby increasing the specific surface area and improving the exposure of active site. In addition, the positively charged surface of CPEZN effectively adsorbed molybdenum ions. Experimental results showed that the introduction of ZIF-8-NH2 improved the adsorption performance of the composites. The adsorption of Mo(VI) followed the Langmuir adsorption isotherm model, and its adsorption rate followed the pseudo-second-order model. The adsorbent exhibited a maximum Mo(VI) adsorption capacity of 872.39 mg/g at pH = 3, and a removal rate of more than 80 % in mixed coexisting ion solutions. Moreover, the adsorbent demonstrated good stability, with a removal rate of above 80 % after 5 cycles of adsorption. Comprehensive characterizations revealed that the adsorption mechanism of Mo(VI) on CPEZN was a synergistic effect of chemisorption, electrostatic interaction, redox, and complex ligand processes. The simulated industrial wastewater adsorption experiment showed that the prepared adsorbent had good removal ability for molybdenum ions. This study not only provides a reference for the design and preparation of MOF and biomass-based composite adsorbent materials, particularly in terms of understanding the adsorption mechanism and designing high-capacity functional groups, but also provides a theoretical basis for its practical application.