Synthesis and Characterization of UiO-66-NH2 (Zr) Metal–Organic Frameworks: Chitosan and its aminated derivatives to remove toxic Cr (VI) from Industrial Wastewater

This study used adsorbent hydrogel beads on chitosan coated with the commercially prepared metal-organic framework (MOF) and its aminated derivative to chromium (VI) ions from their aqueous solutions. Higher removal (%) and higher adsorption capacity values were recorded using chitosan and its aminated derivatives, UiO-66-NH2 (Zr) (0.5 % CS) adsorbent (87 % and 95 mgg-1), respectively, compared with those using CS adsorbent (86% and 93 mg/g using 1% CS); contact time was 180 min, with maximum removal (%) reaching 87% and maximum adsorption capacity of 95 mgg-1. The pH of the studied medium was in the range of 1–8. It was found that the maximum values of removal (%) and adsorption capacity values were observed at pH 2, and the Cr (VI) concentration was studied in the range of 10–200 ppm. The highest removal (%) was about 100 % using 10 and 25 ppm of Cr (VI), while the maximum adsorption capacity was found to be 132 mgg-1 and was recorded using 200 ppm of Cr (VI). Adsorption experiments at 150 rpm were conducted to record maximum adsorption capacity and higher removal (%) values. The developed adsorbent demonstrated good adsorption properties, with removal exceeding 60 % after six cycles and a maximum capacity of 52 mgg-1. In conclusion, the MOF/chitosan adsorbent beads have the potential to be a novel and effective large-scale adsorbent for the removal of hazardous Cr (VI) ions from industrial effluent.