ALTERNATIVE ADSORBENT MATERIALS FOR APPLICATION IN PROCESSES INDUSTRIAL Development of novel sericin and alginate-based biosorbents for precious metal removal from wastewater Nilza Tatiane das Graças Santos 1 & Meuris Gurgel Carlos da Silva 1 & Melissa Gurgel Adeodato Vieira 1 Received: 13 July 2018 /Accepted: 1 October 2018 # Springer-Verlag GmbH Germany, part of Springer Nature 2018 Abstract In this study, two novel low water-soluble sericin and alginate-based biosorbents were successfully developed for precious metal removal from wastewater: sericin and alginate particles chemically crosslinked by proantocyanidins (SAPAs) and sericin, alginate and polyvinyl alcohol particles (SAPVA). The proportions of proantocynidins (PAs) or polyvinyl alcohol (PVA) added to sericin (2.5% w/v) and alginate (2.0% w/v) blend were 0.5, 1.5, 2.5 and 3.5% w/v . Among these concentrations, particles produced with 0.5% w/v of PVA or 2.5% w/v of PAs presented the lowest water solubility percentages (3.74 ± 0.05 and 3.56 ± 0.21%, respectively) and the following metallic affinity order: AuCl 4 - > PdCl 4 2- > PtCl 6 2- > Ag + . Then, gold biosorption kinet- ics by SAPAs was evaluated at three gold initial concentrations (72.88, 187.12, and 273.79 mg/L), and its performance was compared to activated carbon adsorbent uptake. The data modeling revealed that the process follows pseudo-first-order kinetics and is mainly controlled by external diffusion. SAPAs before and after gold biosorption (SAPAs-gold) were characterized by scanning electron microscopy coupled with energy dispersive X-ray spectroscopy, optical microscopy, helium pycnometry, mercury porosimetry, N 2 physisorption, and Fourier-transform infrared spectroscopy. Keywords Biosorption . Precious metals . Sericin and alginate . Gold adsorption . Proanthocyanidins . Polyvinyl alcohol Introduction Effluents containing precious metals in trace amounts are gen- erated in large volumes in industrial activities, such as mining, mineral and metal processing, electronic manufacturing, and e-Waste recycling (Chen et al. 2011; Abdelbasir et al. 2018). Considering precious metal scarcity in the earth’ s crust, high economic value, and elevated industrial demand, their remov- al from wastewater, for reuse purposes, results directly in en- vironmental (Cayumil et al. 2016) and economic benefits (Das 2010). Therefore, searching for a treatment technique that en- ables efficient removal for future recovery of precious metals is crucial (Tappin et al. 2010; Cantuaria et al. 2016). Among several separation technologies, biosorption has drawn attention since it is an efficient, inexpensive, and environmentally friendly process that allows the use of diverse types of waste materials as biosorbents (Gurung et al. 2012; Michalak et al. 2013; Rossi et al. 2018). Although there are many papers in literature reporting the use of biosorption for metals removal from wastewater, there is an ever increasing need to develop efficient and low cost biosorbents aiming at precious metal removal and recovery from wastewater. A promising alter- native for precious metal removal from aqueous environment is sericin and alginate-based biosorbents due to its affinity for sev- eral ionic metals (Silva et al. 2016, 2017). Sericin is a globular water-soluble protein that composes 15– 35% of Bombyx mori cocoon weight (Cao and Zhang 2016). This protein surrounds the two fibroin filament structure in suc- cessive layers (Lewin 2007), which guarantees the fiber union and consequently cocoon formation and cohesion (Zhang 2002). Regarding its secondary structure, sericin is mainly composed of random coil structure and to a lesser extent, β-sheet structure (Padamwar and Pawar 2004). Sericin is a waste material from silk processing in textile industries (Aramwit et al. 2012). Despite being a waste, it has interesting characteristics (Zhang 2002; Aramwit et al. 2012), including easy crosslinking and blending with other polymeric materials, which may result in biodegrad- able products with improved properties (Dash et al. 2009). Responsible editor: Tito Roberto Cadaval Jr * Melissa Gurgel Adeodato Vieira melissagav@feq.unicamp.br 1 School of Chemical Engineering, University of Campinas (UNICAMP), Cidade Universitária Zeferino Vaz, Campinas, São Paulo 13083-852, Brazil Environmental Science and Pollution Research https://doi.org/10.1007/s11356-018-3378-z