Selective adsorption and synchronous reduction of Au from water with difunctional cellulose aerogel: Performance and mechanism

Here, valonia tannin and sulfhydryl functional groups were added to the cellulose aerogel from waste textiles to form a thiol-modified tannin-immobilized cellulose-based aerogel (TVTCA) with selective adsorption and outstanding reducing properties. This aerogel was then utilized to recycle Au(III) in the water. The resulting 3D TVTCA contained abundant -SH groups and phenolic hydroxyl groups and exhibited stable crystal structure and good thermal properties. TVTCA showed excellent Au (Ⅲ) adsorption performance (598.3 mg/g of maximum adsorption capacity) and strong reductivity (78 %). The adsorption process was conducted using both the pseudo-second-order kinetic model and the Langmuir adsorption isotherm model. In addition, TVTCA displayed excellent anti-interference ability. Even though the coexisting ions concentration was as high as 100 mmol/L, TVTCA still owned a high Au adsorption capacity (178.91–224.14 mg/g) and selectivity factor (29.16–2629.34), which was much higher than valonia tannin-immobilized cellulose-based aerogel (VTCA). Furthermore, the recycling of Au with TVTCA mainly included adsorption and in-situ reduction processes. The mechanisms involved the electrostatic interaction and chelation effects, which were ascribed to the introduced sulfhydryl groups. Meanwhile, the in-situ Au reduction was mainly caused by the studies showing that the high adsorption capacity of TVTCA was owing to the phenolic hydroxyl groups on the introduced valonia tannin. All the findings would provide a new way to achieve the recycling of precious metals from wastewater by using valuable cotton waste.