Morphological diversity effect of graphene quantum dot/MIL88A(Fe) composites on dye and pharmaceuticals (tetracycline and doxycycline) removal

Herein, composites with different morphologies (diamond-like, rod-like, and spindle-like) were successfully synthesized using MIL88A (Fe) and graphene quantum dots (GQDs) to remove Acid Blue 92 (AB92), pharmaceuticals (doxycycline, and tetracycline). Despite the similarity in content, chemical structure, and functional groups of the composites, interesting differences were observed in some of their physicochemical properties (BET, RAMAN, TEM, and SEM) and adsorption performance, which was the turning point of this research. Spindle-like GQDMIL88A composite with the adsorption capacity of 617 mg/g indicated the highest adsorption capacity for Acid Blue 92 (AB92) compared to 335 mg/g for rod-like composites and 114 mg/g for diamond-like composites. Also, for doxycycline removal, the spindle-like composite with the adsorption capacity of 796 mg/g, was still in the first rank, compared to 588 mg/g for rod-like and 469 mg/g for diamond-like GQDMIL88A. The tetracycline adsorption capacity for spindle-like, rod-like, and diamond-like GQDMIL88A composites was 672 mg/g, 398 mg/g, and 300 mg/g, respectively. According to the findings of this study, despite the different adsorption capacities of different GQDMIL88A composite morphologies, all three types are well compatible with the Langmuir isotherm and pseudo-second-order kinetics.