Facile synthesis of ATTM@ZIF-8 modified pullulan hydrogels for enhanced adsorption of Congo red and malachite green.

Efficient capture of dyes from wastewater is of great importance for environmental remediation. Yet constructing adsorbents with satisfactory adsorption efficiency and low cost remains a major challenge. This work reports a simple and scalable method for the fabrication of functionalized porous pullulan hydrogel adsorbent decorated with ATTM@ZIF-8 for the adsorption of congo red (CR) and malachite green (MG). The embedding of ammonium tetrathiomolybdate (ATTM) into the ZIF-8 nanoclusters offered additional adsorption sites and enlarged the pore size of the resulting ATTM@ZIF-8. The homogeneous dispersion of the nanoparticles in the three-dimensional network of polysaccharide gels prevents their agglomeration and thus improves the affinity for dye molecules. The resulting adsorbent AZP-20 at optimized composite ratios exhibits high activity, selectivity, interference resistance, reusability and cytocompatibility in dye adsorption applications, and possesses high removal rate of dye in real water systems. Batch experiments demonstrated that the adsorption rate of AZP-20 for MG and CR was 1645.28 mg g-1 and 680.33 mg g-1, and would be influenced by pH conditions. Adsorption kinetics followed pseudo-second-order model. Adsorption isotherms followed Langmuir model for MG and Freundlich model for CR. The adsorption of dye molecules primarily relied on electrostatic interaction (MG) and π-π stacking interaction (CR). Conclusively, the prepared AZPs adsorbent illuminated good application prospects in the treatment of complex component dye wastewater.

High-capacity adsorption of organic dyes using separable pullulan gel encapsulated with PDA-modified ZIF-8.

In this investigation, a hydrogel adsorbent featuring remarkable efficiency in dye adsorption was successfully synthesized by the integration of natural polysaccharide (pullulan) and nanoparticles (ZIF-8@PDA). The prepared natural polysaccharide nanocomposite hydrogels not only exhibit superior mechanical strength and biocompatibility, but also demonstrate adeptness in the removal of dye pollutants. The dye removal capacities were 615.4 mg/g for malachite green (MG) and 525.8 mg/g for Congo red (CR), respectively. Notably, the adsorption process exhibits minimal susceptibility to variations in water quality and the presence of co-existing ions. The pH-responsive surface charge conversion capability of the adsorbent renders it recyclable, maintaining a dye adsorption performance exceeding 88 % even after 5 cycles of repeated usage. Overall, these environmentally friendly natural polysaccharide nanocomposite hydrogels hold potential for addressing complex wastewater treatment challenges and long-term use.