Modeling of the Bioleaching of Process Silver Pulp

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Modeling of the Bioleaching of Process Silver Pulp

A new model for the bioleaching process of silver is used to theoretically describe available experimental data. The model is based on the two-moving-front description of mineral bioleaching. The model quantitatively predicts the evolution of the silver mass fraction and the minimum in the biofilm mass fraction, related to the maximum in the rheological properties.


Abstract

Modeling of the bioleaching process applied to the system silver-manganese (Ag-Mn) was carried out. The two-moving-fronts model was used to describe the main stages of the process. Bioleaching involves a catalytic process carried out by bacteria to dissolve the mineral ores. Initially, the bacteria interact with the mineral to dissolve manganese, leading to the precipitation of silver. The Ag-Mn compound is dissolved by the bacteria in two stages. First, the bacteria dissolve the manganese and form a biofilm composed mostly of exopolysaccharides. In the second stage, the biofilm is consumed by the bacteria, ending up in dissolved manganese and silver precipitation. At 48 h, the viscosity of the pulp reaches a maximum attributed to the maximum concentration of extracellular polysaccharides in the medium. Predictions describe the basic issues of the bioleaching process in this system.

Thixotropic Hydrogels Based on Laponite® and Cucurbituril for Delivery of Lipophilic Drug Molecules

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Nowadays the use of hydrogels for biomedical purposes is increasing because of their interesting features that allow the development of targeted drug delivery systems. Herein, hydrogel based on Laponite (Lap) clay mineral as gelator and cucurbit[6]uril (CB[6]) molecules were synthetized for the delivery of flufenamic acid (FFA) for potential topical application. Firstly, the interaction between CB[6] and FFA was assessed by UV-vis spectroscopic measurements and computational calculations. Then, the obtained complex was used as filler for Lap hydrogel (Lap/CB[6]/FFA). The properties of the hydrogel in terms of viscosity and, self-repair abilities were investigated; their morphology was imaged by scanning electron and polarized optical microscopies. Furthermore, the changes in the hydrodynamic radii and in the colloidal stability of CB[6]/Lap mixture were investigated in terms of translational diffusion from dynamic light scattering and z-potential measurements. Finally, the kinetic in vitro release of FFA, from Lap/CB[6]/FFA hydrogel, was studied in a medium mimicking the pH of skin and the obtained results were discussed both by an experimental point of view and by computational calculations.

5‐Sulfurated Imidazo[1,5‐a]Pyridin‐3‐ylidenes: Ligands for π‐Acidic Catalysts

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5-Sulfurated Imidazo[1,5-a]Pyridin-3-ylidenes: Ligands for π-Acidic Catalysts


Abstract

A series of 5-sulfurated imidazo[1,5-a]pyridin-3-ylidenes (Imidazo[1,5-a]pyridine carbenes: IPCs) and their Cu and Pd complexes were synthesized. Theoretical investigations of the free carbenes and Cu complexes implied that the IPCs were good π-acceptors. Particularly, Cu complexes of 5-arylsulfonyl IPC were strong π-acids. These complexes were tested as π-acidic catalysts in the Cu-catalyzed hydroboration of an internal alkyne with diboron and the Mizoroki-Heck reaction. As a result, the trend in reactivity corresponded with the theoretical considerations.

Protecting Group‐Free Gold‐Catalyzed Synthesis of 2‐Acylidene‐3‐Oxindoles and Azaaurones via a Double Oxidation Strategy

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Protecting Group-Free Gold-Catalyzed Synthesis of 2-Acylidene-3-Oxindoles and Azaaurones via a Double Oxidation Strategy


Abstract

A one-pot synthesis of 2-acylidene-3-oxindole and azaaurone derivatives starting from O-alkynylanilines and alkynes is presented. By means of oxidative gold catalysis the two starting materials are transferred to reactive intermediates that in situ form the target products. This double oxidation strategy enables a protecting group-free step-economic strategy towards these valuable substrate classes.