Voltammetric monitoring of laccase-catalysed reactions of different lignins through oxidative coupling with glucosamine

The ability of laccase to facilitate grafting hydrophilic compounds, namely glucosamine to lignin in acetone/water mixtures aiming to obtain grafted novel lignin derivatives with new functionalities was assayed by cyclic voltammetry. The oxidation properties registered for the oxidative reactions of syringaldazine lignin model compound with glucosamine evidenced that the reaction scan is direct proportional with the redox potential differences between substrate and laccase. A comparative electrochemical activity of lignins on the GCE in absence and presence of the laccase and glucosamine is presented. From the measurements of the coupling reactions currents it was concluded that the addition of glucosamine can lead to a partial loss of the redox activity of lignin phenolic groups and the co-substrate interaction with the lignin surface groups

Artichoke extract as corrosion inhibitor for carbon steel in acid media

The aim of this investigation is to examine the inhibitory effect of artichoke extract toward the corrosion of carbon steel corrosion in 0.5 M sulfuric acid solution. Potentiodynamic polarization and crhonoamperometry techniques were used in this work to evaluate the inhibition efficiency of the proposed inhibitor in acid solution. Also, Tafel method for the kinetic parameters determination

Capsaicin extract ss corrosion inhibitor for carbon steel in sodium chloride aqueous solution

In this paper are presented preliminary results obtained using capsaicin extract as corrosion inhibitor for carbon steel in sodium chloride aqueous solution. Capsaicin is a chili pepper extract with analgesic properties. The electrochemical behavior of capsaicin in sodium chloride solution was examined by cyclic voltammetry Further, the inhibitory effect was studied by linear polarization and Tafel method in order to determin the kinetic parameters, providing informations about the the mechanism of inhibitory effect. The diminution of corrosion rate of carbon steel in the presence of capsaicin can be attributed to the inhibitor molecules adsorbtion on the sample surface and blocking the active sites, or depositing corrosion products on the metal surface

Enzymatic modification of lignin and lignin fractions obtained from preatreated biomass

The potential for using Trametes versicolor laccase to graft the polysaccharide chitosan onto chemically fractionated lignin was examined to enhance the solubility of lignin and to obtain products with special properties. Due to the complexity of lignin molecule the reaction was first performed on lignin model compound with small molecular weight. The efficiency of the enzyme was investigated in the oxidative reactions of coniferyl alcohol with glucosamine. Alcell Lignin was previously fractionated by acetone/water 50:50 (v/v) and the enzymatic modification of the soluble fraction with chitosan was carried out in the same solvent system. The modified lignin was isolated and the product was characterized by means of size exclusion chromatography and FT-IR in order to evidence the main lignin modifications after laccase coupling reactions. An important increase of the molecular weight and significant structural modifications were observed for the product obtained after the coupling reactions of Alcell Lignin with chitosane demonstrating the achievement of the modification reactions

Corrosion of carbon steel OLC 45 and stainless steel aisi 304L in wines from Banat county

In the present paper, results on the corrosion rate of carbon steel OLC 45 (similar to EU C 45) and stainless steel AISI 304L in a few species of wines from Banat County (Romania) have been emphasized. Corrosion rates have been determined using weight loss measurements, as well as Tafel plots method. The effect of wines on the surface of studied steels has been revealed using scanning electron microscopy. The obtained results show that the values of the corrosion rates in the wines tested for OLC 45 are close to the maximum allowed limit, which means that this type of steel cannot be used in the wine processing and storage. On the contrary, the corrosion rates for AISI 304L steel are extremely low in all the analyzed wines, which proves that they can be used both for wine processing and storage

Resveratrol as corrosion inhibitor for metals in wine and food industries

This paper presents preliminary results obtained in the case of Resveratrol used as corrosion inhibitor for stainless steel, carbon steel, polished and brushed aluminum in ethanol solutions. Electrochemical behavior of Resveratrol in ethanol solutions has been studied by cyclic voltammetry on platinum electrode. Information about the inhibitory effect mechanism was provided by kinetic parameters calculated with Tafel method from linear polarization curves. Corrosion rate diminution of studied electrodes in the presence of Resveratrol can be assigned to the adsorption of inhibitor molecules on the sample surface, or depositing corrosion products onto metal surface, blocking the active sites