In situ preparation and characterization of Cr-MOF-alginates for methylene blue through the adsorption process

Abstract

One of the increasing environmental worries arises from water pollution caused by synthetic dyes since several colors possess carcinogenic properties. Metal-organic frameworks (MOFs) have attracted considerable attention as adsorbents for removing dyes in wastewater treatment. Nevertheless, the inherent characteristics of MOFs impose limitations on their practical use in terms of recycling, separation, and recovery. To overcome these limitations, MOFs are modified into macroscopic structures. We reported two macroscopic Cr-MOF-Alginate composite beads prepared using the in situ growth method to remove methylene blue from the aqueous solution. The characterization tools confirmed that two different Cr-MOF-Algs formed with different in situ methods and showed distinct MB adsorption. The trials produced the following optimal conditions: an adsorbent dose of 0.3 g, a pH level of 10, a contact length of 120 min, a primary concentration of 10 mgL−1 for MB, and a temperature of 25 °C. In these circumstances, the maximum MB removal percentages reached 90.33 %, 93.42 %, and 94.06 % for Cr-Alg, Cr-BTC/SA-R, and Cr-BTC/SA-A, respectively. Additionally, various isotherms and kinetics implied that the adsorption of MB onto Cr-Alg and Cr-MOF-Alg composite beads occurs through chemisorption and physisorption. Thermodynamic analysis revealed that the adsorption process exhibited an endothermic and spontaneous nature.