Carbohydrate-supramolecular gels: Adsorbents for chromium(VI) removal from wastewater

Hypothesis: To overcome the contamination of water by heavy metals the adsorption of the pollutant ongel phases is an attractive solution since gels are inexpensive, potentially highly efficient and form a distinctphase while allowing diffusion of the contaminated water throughout the material. This work teststhe chromium(VI) adsorbent capacity of new supramolecular gels for Chromium(VI) removal fromwastewater.Experiments: First hydrophobic imidazolium salts of carbohydrate anions were synthesised as new gelators.Subsequently, they were dissolved in a solvent by heating and, after cooling overnight, to give theformation of supramolecular gels. The properties of the resulting gels, such as thermal stability, mechanicalstrength, morphology, rheology, and kinetics of gel formation, were studied as a function of gelatorstructure, gelation solvent and pollutant removal efficiency.Findings: Carbohydrate-derived gels showed the best removal capacity, i.e. 97% in 24 h. Interestingly, inone case, the reduction of chromium(VI) to chromium(III) also occurred after the adsorption process, andthis phenomenon has been analysed using 1H NMR spectroscopy, IR spectroscopy, and SEM. The mostefficient gel can reach an adsorption capacity of 598 mg/g in contrast to a value of 153 mg/g for the mosteffectively best hydrogels reported to date. The new gel can be also recycled up to 4 times. These findingssuggest that these new, supramolecular hydrogels have potential applications in environmentalremediation.