Adsorption of Gold Ions onto Sericin and Alginate Particles Chemically Crosslinked by Proanthocyanidins: a Complete Fixed-Bed Column Study

In this study, we evaluated the adsorption of gold ions onto sericin and alginate particles chemically crosslinked by proanthocyanidins (SAPAS) in a fixed-bed column aiming at establishing a new profitable application for sericin. The effects of the feed flow rate and the gold inlet concentration on the breakthrough curve behavior were investigated. A breakthrough time of more than four and a half days with a removal efficiency of 98.39% (maximum removal capacity of 57.91 mg/g) was obtained for the breakthrough curve performed at the lowest feed flow rate and the lowest gold inlet concentration (0.4 mL/min and 53.18 mg/L, respectively). All breakthrough curves were best described by the Yan et al. model. The two adsorption/desorption cycles performed using thiourea (0.5 M)/hydrochloric acid (0.5 M) as the eluent resulted in low values of gold recovery percentage (recoveries of 24.98 and 22.6% for the first and second cycle, respectively), which indicated the predominance of chemical interactions between SAPAS and gold. On the other hand, an efficient recovery of gold (89.00%) was achieved from the association between the adsorption and incineration processes. X-ray photoelectron spectroscopy and X-ray diffraction analyses indicated that gold was reduced from Au­(III) to metallic gold during the adsorption process.