The synthesis of
metal nanoparticles via greener and sustainable
methods has gained a great attention because of the use of natural
products which are nontoxic and environmentally benign. Though many
efforts have been made to prepare nanostructures employing plant extracts
rich in polyphenols, their role in the formation of nanoparticles
has not been fully investigated. This paper demonstrates a route of
size-controllable synthesis of copper nanoparticles (CuNPs) using
(+)-catechin solution and the chemistry behind the reaction. Altering
pH of process parameters allowed for the formation of nanoparticles
with sizes ranging from 3 to 40 nm evaluated by high-resolution transmission
electron microscopy. The results revealed that the higher the pH,
the smaller and the more stable nanoparticles are obtained. Higher
concentrations of copper(II) ions [Cu(II)] created larger nanostructures
which tended to aggregate. Stable, monodisperse CuNPs with a diameter
of about 3 nm were obtained for a (+)-catechin to a Cu(II) molar ratio
of 2:1 and pH 11. HPLC analysis showed that (+)-catechin solution
at pH 11 contains procyanidins as major phenolic components, and their
type and content depend on the presence of copper(II) ions. The proposed
mechanism of CuNP synthesis reaction involves pH-dependent oxidation
of (+)-catechin and simultaneous reduction of Cu(II).
Abstract. Serpentinites have the potential to be used as carbo dioxide capture and storage materials. Acid dissolution is the first stage of this process. This study examined how a shrinking core model can be applied to the dissolution of serpentinite in sulphuric acid. The dissolution process was assumed to occur in two stages: an initial step involving the surface dissolution of serpentinite pieces, and a second step involving surface chemical reaction, described by the shrinking core model. The model formulation was completed by relating the dissolution rate of serpentinite to the surface changes.
Bacterial cell adhesion onto mineral surfaces is important in a broad spectrum of processes, including bioweathering, bioleaching, and bacterial cell transport in the soil. Despite many research efforts, a detailed explanation is still lacking. This work investigates the role of surface-active compounds, cetyltrimethylammonium bromide (CTAB), sodium dodecyl sulfate (SDS), and pure rhamnolipid (RH), in the process of bacteria attachment on the schwertmannite surface. The surface energy was calculated based on the wettability of the tested systems, and for bacteria it was 54.8 mJ/m2, schwertmannite-SDS 54.4 mJ/m2, schwertmannite-CTAB 55.4 mJ/m2, and schwertmannite-RH 39.7 mJ/m2. The total energy of adhesion estimated based on thermodynamic data was found to be negative, suggesting favorable conditions for adhesion for all examined suspensions. However, including electrostatic interactions allowed for a more precise description of bacterial adhesion under the tested conditions. The theoretical analysis using the extended Derjaguin-Landau-Verwey-Overbeek (DLVO) approach showed a negative value of total adsorption energy only in bacteria-mineral suspensions, where SDS and rhamnolipid were added. The calculated data were in good agreement with experimental results indicating the significance of electrostatic forces in adsorption.
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