This research was supported by the Phosagro/UNESCO/IUPAC Partnership in Green Chemistry for Life (Contract ). JCFRR acknowledges the support of 4500245048FONDECYT and the World Bank (Contract 106-2018).The participation of GL was possible through the Real Life Experience (RLE) program at UTEC. Karinna Visurraga is thanked for administrative support.

In spite of the widespread use of the chemical reduction method to obtain silver nanoparticles, the nanoparticle yield is often low due to a required addition of small volumes of diluted metal ions to a solution containing a reducer. Higher yields can be obtained following an alternative method, in which the reducer is added to a greater volume of silver ions in the solution. In this study, protocols for both methods are detailed and compared, using characterization tools such as UV-vis spectrometry, dynamic light scattering (DLS), and zeta potential measurements. By using this alternative method, the amount of silver in the solution is three times greater, and nanoparticles with a narrower size distribution are formed (between 6 and 70 nm in size). In contrast, the regular method produces particles of 3 and 100 nm. Zeta potential measurements indicate that the nanoparticles synthesized ...

Cultural heritage materials are affected by diverse environmental agents such as humidity, temperature, and pollution. This work focuses on studying the thermodynamic stability of Peruvian heritage materials such as gilded coppers and pigments within two scenarios: one under ambient conditions and the other under accelerated conditions established by the ASTM D 2247 standard. In both cases, the HSC Chemistry 6 software was implemented. The general results obtained for gilded coppers showed that by varying the relative humidity from 75% and 14 °C to 80% and 26 °C, the corrosion products move from CuO to Cu(OH) 2. In addition, to Cu2Cl(OH)3-Atacamite-in the presence of chlorin. On the other hand, for hematite (Fe 3O 2), vermilion (HgS), and Minium (Pb 3O 4) pigments, we found that at ambient conditions, with NO 2 and SO 2, they give rise to goethite (FeO(OH)), mercury sulfate (HgSO 4) an...

The leaching of valuable metals from mineral ores is the basis of several extractive economies around the world, but the strategies employed often need to rely on dangerous compounds such as cyanides. Due to the complex nature of most ores, leaching processes are slow and have a low efficiency in noble metal extraction, which is usually improved by fine-milling the mineral. In this manuscript, we consider this strategy, demonstrating that it may increase the amount of silver leaching, but at the expense of a higher consumption of cyanide, which renders the process inefficient (only 2% of consumed cyanide is employed to complex silver). The increase in the yield of the desired product without the smarter use of dangerous compounds is shown as a paradigm of the need to insert green chemistry principles in industrial processes. We further present the result of two potential strategies for g...

This work has been supported by Peru's Consejo Nacional de Ciencia y Tecnologia (CienciActiva - CONCYTEC) and the British Embassy in Lima [contract numbers 154-2015 and 002-2016]. Portions of this research were conducted with the advanced computing resources provided by Texas A&M High Performance Research Computing. Ms. Karinna Visurraga (UTEC) is kindly acknowledged for administrative support.

Cyanidation (leaching with cyanide) is a common yet complex surface process in hydrometallurgical practice, and its effectiveness in extracting the metal of interest is often affected by the nature of the mineralogical species that are present. Little is known about surface processes on acanthite (a silver sulfide) and how its various facets respond to cyanidation in aqueous solution. Therefore, in this work, some properties of both bulk acanthite (Ag2S) and its (001), (022), and (1̅21) surface facets have been studied by density-functional-theory (DFT)-based calculations to elucidate reactivity trends and competitive adsorption (initial stages in the surface process of cyanidation) between cyanide and other species present in the leaching liquor. It is found that CN– binds by its C-end to silver sites on the acanthite surface with adsorption energy similar to that of OH– but strong...

Strategies to design novel antibacterial materials may rely on the combination of materials to achieve synergistic effects. The coupling of antibacterial peptides to nanoparticles, however, needs to be directed conveniently to avoid structural changes within the peptide and/or degradation of the nanoparticle. Here, we present the results of the attachment of a synthetic peptide (VIHGW-alkyne-G-NH2) containing the amino terminal copper and nickel (ATCUN) motif to silver nanoparticles. In order to direct the peptide-nanoparticle coupling, the peptide was functionalized with an alkyne, whereas the nanoparticles were functionalized with azide groups using thiol-polyethylene glycol-azide (HS-PEG-N3) chains, so that the acetylide and the azide can undergo a click reaction. The reaction was conducted at room temperature and the steps in the construction of the nanoparticle-PEG-ATCUN array were ...

Understanding the changes of a mineral during ore processing is of capital importance for the development of strategies aimed at increasing the efficiency of metal extraction. This task is often difficult due to the variability of the ore in terms of composition, mineralogy and texture. In particular, surface processes such as metal re-adsorption (preg-robbing) on specific minerals are difficult to evaluate, even though they may be of importance as the re-adsorbed material can be blocking the valuable mineral and negatively affect the extraction process. Here, we show a simple yet powerful approach, through which surface processes in individual minerals are identified by combining polarization microscopy (MP) and X-ray photoelectron spectroscopy (XPS). Taking as an example a silver-containing polymetallic sulfide ore from the Peruvian central Andes (pyrite-based with small amounts of gal...

Leaching of polymetallic sulfides is often challenging due to the complexity of these systems. The main issues are related to the formation of surface by-products or to the presence of different metals that require a greater consumption of chemicals compared to that needed to extract the target metal during leaching. This latter case is followed in the present work using X-ray photoelectron spectroscopy (XPS) during the leaching of a silver-containing polymetallic (Mn-Fe-Pb) sulfide under three different cyanidation procedures: (1) conventional leaching, (2) ultrasound-assisted leaching, and (3) leaching of a sample pretreated in alkaline media. In all cases, leaching results in the build-up of Pb compounds (oxides/hydroxides) on the surface of the minerals, suggesting a mechanism in which Pb is first leached by hydroxide and cyanide and later is re-adsorbed as an external layer on the m...