Journal of Hazardous Materials 420 (2021) 126598 Available online 8 July 2021 0304-3894/© 2021 Elsevier B.V. All rights reserved. Biosorption mechanisms of Ag(I) and the synthesis of nanoparticles by the biomass from Botryosphaeria rhodina MAMB-05 Antonio J. Mu˜ noz a, * , Francisco Espínola a, b , Encarnaci´ on Ruiz a, b , Aneli M. Barbosa-Dekker c , Robert F.H. Dekker c , Eulogio Castro a, b a Department of Chemical, Environmental and Materials Engineering, Universidad de Ja´ en, Campus Las Lagunillas, 23071 Ja´ en, Spain b Centre for Advanced Studies in Earth Sciences, Energy and Environment (CEACTEMA), Universidad de Ja´ en, Campus Las Lagunillas, 23071 Ja´ en, Spain c Beta-Glucan Produtos Farmoquímicos - EIRELI, Lote 24A, Bloco Zircˆ onia, Universidade Tecnol´ ogica Federal do Paran´ a, Avenida Jo˜ ao Miguel Caram 731, CEP: 86036- 700 Londrina, Paran´ a, Brazil A R T I C L E INFO Editor: Dr. R. Debora Keywords: Residual biomass Silver Biosorption Ag/AgCl-NPs, XRD ABSTRACT Two biomass types of Botryosphaeria rhodina MAMB-05 (VMSM and M3) were evaluated to determine their effectiveness in removing Ag(I) ions from synthetic solutions. Both biomass types obtained good results in the biosorption process with maximum biosorption capacities (q m ) for the Langmuir model of 34.67 and 39.23 mg Ag(I)/g dry biomass for M3 and VMSM, respectively. The biomass was characterized by X-ray microfuorescence and Fourier-transform-infrared spectroscopy (FT-IR). After the biosorption process, the mechanisms involved in biosorption were studied by FT-IR, X-ray diffraction (XRD), Field Emission Scanning Microscopy/Energy Dispersive X-ray Analysis (FESEM/EDX) and Ultraviolet-Visible Spectrophotometry. The results demonstrated the participation of various mechanisms in the retention of silver on biomass (bioadsorption, complexation, ion exchange, covalent bonding) that resulted in the formation of silver chloride nanoparticles (AgCl-NPs) and silver nanoparticles (AgNPs). The sizes of AgCl-NPs (chlorargyrite) according to the Debye-Scherrer equation were 19.29 nm (VMSM biomass) and 24.9 nm for the M3 type. For AgNPs the crystal size was between 1.5 and 0.8 nm for VMSM and M3 respectively. Furthermore, it was found that an undetermined fraction of the silver nano- particles after biosorption remained in solution, which could be advantageous for their recovery. 1. Introduction In recent decades, and at the international level, a legislative framework has been developed to promote the reduction of all types of pollutants discharged into the environment. The reality, however, is that these pollutants continue to constitute one of the most relevant envi- ronmental and safety problems today. Among the pollutants are the heavy metals that are frequently used in most industrial processes and their use has no ecological alternatives. Some studies have shown that in many cases, the concentrations of heavy metals in the natural environ- ment have been increasing over the years (Li et al., 2019). Heavy metals can spread through the air (aerosols) and can also be discharged into soils and waters where they later circulate dissolved in surface and groundwater, thus affecting all natural ecosystems (Wai et al., 2017; Rajkumar et al., 2020; Hoang et al., 2020). The bioaccumulative char- acter of many heavy metals means that they can be incorporated into the trophic chain ranging from the microbiota of soils, sediments and waters, passing through the food chain (crustaceans, fsh, plants and animals) until they reach humans (Skipin et al., 2016; Maurya et al., 2019; Kumar et al., 2019). Conventional techniques for removing heavy metals are mainly based upon physicochemical processes, and are effective only when the pollutant is present at high concentrations (>100 mg/L), but these are also expensive and can generate polluting residues that in many cases must be subsequently removed in a controlled manner. Most of the physicochemical processes, however, are ineffective at low concentra- tions of heavy metals (Beni and Esmaeili, 2020). For this reason, alter- native heavy metal-removal processes such as those based upon biosorption that makes use of different types of microbial and plant biomass have been studied for decades. Biosorption can be defned in several ways, but in a general way it involves a series of interactive mechanisms dependent (bioaccumulation) and independent (bio- adsorption) of cellular metabolism between biomass (sorbent) and contaminants that are generally dissolved in the liquid phase (sorbate). * Corresponding author. E-mail address: amcobo@ujaen.es (A.J. Mu˜ noz). Contents lists available at ScienceDirect Journal of Hazardous Materials journal homepage: www.elsevier.com/locate/jhazmat https://doi.org/10.1016/j.jhazmat.2021.126598 Received 2 April 2021; Received in revised form 1 July 2021; Accepted 5 July 2021