Synthesis of a novel fibrous material for effective Au(III) recovery with superior selectivity and one-step reduction

To synthesize a material for effective Au(III) recovery with excellent selectivity and one-step reduction from solution remains a huge challenge. In this study, a novel fibrous material was synthesized by treating carbon nanofibers with ammonia-plasma followed by N-Aminorhodanine assembly; it was used for Au(III) recovery by sorption. The results demonstrated that the maximum sorption capacity of Au(III) by the N-Aminorhodanine assembled-carbon nanofibers (N-AMCNFs) reached 229 mg/g, which is 20.6 times that by carbon nanofibers (11 mg/g). Excellent Au(III) recovery by N-AMCNFs mainly resulted from its extremely hydrophilic nature indicated by a contact angle of 2.69 degrees and the newly-introduced N- and S-containing soft base moieties (-C-N, -C--N, -C-S and -C--S). These sites provided electrons for coordination chelation with soft acid Au(III). Electrostatic attraction between AuCl4- and the positively-charged N-AMCNFs also served as a driving force for Au(III) recovery. Importantly, 44.3% of Au(III) was reduced to Au(0) by electrons transferred from S- and N-sites on rhodanine during sorption, as proved by XRD and XPS analysis. Besides, N-AMCNFs exhibited superior recovery selectivity indicated by above 96.24% recovery efficiency for Au(III) at pH 4 in the presence of multiple interfering ions including Cu(II), Ni(II), Zn(II), and Pb(II) at 50 mg/L as Au(III), but their recovery was below 2%.