Free sulfur-containing terminal groups as exclusive trapper of Au

Abstract

Thanks to the high affinity, adsorbents with sulfur-containing groups are usually used to recover Au ions, but neglect of the availability and utilization of introduced groups often makes the effort wasted, limiting the practical application of adsorbents severely. Here, we designed and fabricated two ANF-based aerogels with free and anchored thiourea groups respectively, and the adsorption performance and key influence factors were investigated by combining experiments and MD simulations. The experimental results showed that two aerogels exhibited distinct performance of adsorbing Au ions. And MD simulations results disclosed the structure difference of thiourea groups on the surface of two aerogels. The one with better performance had freer sulfur-containing groups, and these groups were easy to change their conformation, resulting in easier interaction with Au ions. However, groups on the surface of the other one were anchored. This difference in structure and resultant performance indicated that the freedom of functional groups play a critical role in the process of adsorption. As a result, the calculated maximum adsorption capacity of aerogels with free thiourea groups is as high as 719.42 mg/g, and although the reusability of adsorbents decreases with the increase of recycle times, caused by the generation of Au (0) during adsorption process, its adsorption capacity is till as high as 461.9 mg/g. Alternatively, incineration is also a feasible approach, especially after several recycle times, because of the low cost of fabricated adsorbents. Therefore, aerogels prepared by structural design have advantages in the field of gold recovery, and the superior performance also demonstrates the significance of utilization of introduced functional groups in the designed adsorbents.