Adsorption of dihydroxybenzene isomers over Schiff-based network-1-derived nitrogen-enriched carbon: Effective and favorable adsorption of hydroquinone

초록

Urbanization and modernization through intense industrial activity led to the disposal of harmful and nonbiodegradable organic substances including dihydroxybenzene isomers such as hydroquinone, catechol, and resorcinol. A covalent-organic polymer Schiff-based network-1, SNW1 was synthesized, pyrolyzed, and subsequently carbonized again, after mixing with KOH, at 800 degrees C. The obtained carbon, prepared in two-stepcarbonization (named as SNW1-2DC), was applied to the adsorption of dihydroxybenzene isomers; showed remarkable performance in hydroquinone adsorption with the maximum adsorption capacity ( Q 0 ) of 1060 mg/g at neutral conditions. This Q 0 is 6.0 and 5.5 times that of activated carbon and the carbon obtained from the simple pyrolysis of SNW1, respectively; of note, this value represents the highest compared to any previously reported findings. Moreover, the regenerated adsorbent, with simple ethanol washing, performed well for up to 5 cycles. This material could be suggested as a promising adsorbent in hydroquinone removal from water. The adsorption mechanism, including hydrogen bonding, could be suggested. Interestingly, the performance of SNW1-2DC in the adsorptive removal of catechol and resorcinol was very low in comparison with that of hydroquinone. The relative adsorption performances of SNW1-2DC for dihydroxybenzene isomers could be explained with density functional theory calculation and thermodynamic parameters. The most favorable hydroquinone adsorption (among the three dihydroxybenzene isomers) over SNW1-2DC might be because of less endothermic adsorption and more effective H-boning interaction between hydroquinone and SNW1-2DC than that between catechol or resorcinol and the adsorbent.

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