Efficient fabrication of a composite sponge for Cr(VI) removal via citric acid cross-linking of metal-organic framework and chitosan: Adsorption isotherm, kinetic studies, and optimization using Box-Behnken design

Abstract

To establish a proficient technique for adsorbing Cr(VI) from water solutions, we altered silver metal-organic frameworks (Ag-MOF) by enveloping sulfadoxine within chitosan, producing a composite sponge referred to as NH2–Ag-MOF@CSC. The NH2–Ag-MOF@CSC composite sponge, synthesized and examined through SEM, XRD, FTIR, and BET, demonstrated a substantial surface area of 862.87 m2/g, as confirmed by these analyses. Following that, it was applied to wastewater systems as an adsorbent to eliminate Cr(VI) ions. The ideal adsorbent dose, temperature and pH were examined by means of batch mode research. High adsorption capacity and clearance efficiency were noted at pH 4, 0.02 g/25 mL dose, and 100 min for communication time. The Qmax adsorption capacity for Cr(VI) via the NH2–Ag-MOF@CSC composite sponge was 382.6 mg g−1. Both the Langmuir isotherm and pseudo-second order kinetics were adjusted to the process of adsorption. On the other hand, chemisorption was the adsorption method as the adsorption energy was 22.42 kJ mol−1. Thermodynamic calculations demonstrated that the removal of Cr(VI) was endothermic as well as spontaneous, exhibiting a positive ΔSo value indicating the disorder at the interface of the solid solution throughout the adsorption. Moreover, the ΔGo gets increasingly negative as the temperature rises. Examine how π-π interaction, hydrogen bonding, electrostatic interaction and pour filling, occur related to the mechanism of adsorption. This adsorbent was thought to be inexpensive because it could be used effectively for up to six cycles. Chemical stability was a key factor in reusability because the XRD pattern before and after regeneration could not be distinguished from one another. Furthermore, there was no change in the function group and the FT-IR remained stable. To optimize the adsorption outcomes, Box Behnken design was employed (BBD).