Treatment of galvanic effluent through electrocoagulation process: Cr, Cu, Mn, Ni removal and reuse of sludge generated as inorganic pigment.

Galvanic effluents are composed of a wide range of heavy metals, requiring adequate treatment to remove these contaminants and to meet the limits established by environmental agencies. Considering this aspect, the present study had as main objectives: (i) to evaluate the efficiency of the electrocoagulation (EC) in the treatment of a galvanic effluent, with the purpose of removing total Cr, Cu, Mn, Ni and (ii) reuse the sludge generated for inorganic pigment production. EC tests were carried out through factorial design 23 with triplicate central point. pH (3, 7, 11), reaction time (15, 22.5 and 30 min) and current density (10, 17.5 and 25 mA/cm2) were the control variables. Under ideal experimental conditions (pH 7.00; t = 22.5 min and DC = 17.5 mA/cm2) were removed 96.94% of Mn, 97.63% of Cu and 99.99% of total Cr and Ni, allowing to meet the limits provided in CONAMA Resolution 430/2011. The production of inorganic pigments from a mixture of 10% sludge (generated in the ideal experimental condition) and Al2O3 and TiO2 proved to be technically viable. It was obtained 8.27 g of a brown inorganic pigment, composed mainly of Al1.82Cr0.18O3, Ca0.999(Ti0.805Fe0.201)O2.899 and Fe2.18O4Ti0.42. Therefore, the results obtained demonstrate that EC is an effective technique in galvanic effluents treatment. The sludge generated in this process showed to be appropriated to be reused in inorganic pigment production and could be considered as an alternative to reduce the environmental impact related to electroplating process.

Gelatin/poly(vinyl alcohol) based hydrogel film - A potential biomaterial for wound dressing: Experimental design and optimization followed by rotatable central composite design.

The development of hydrogel films for biomedical applications is interesting due to their characteristics. Hydrogel films based on gelatin and poly(vinyl alcohol) (PVA) are developed and characterized using a rotatable central composite design. The optimized hydrogel film is obtained by the function desirability of the Statistica® software and is also characterized by swelling kinetics, oxygen permeability, adhesiveness, TGA, DSC, and XRD. The results of the experimental design show that gelatin and PVA concentrations have a significant influence on the response variables, and the exposure doses to UV light show no significant effect. The optimized hydrogel film is elastic, presents good mechanical resistance and swelling capacity in water and exudate solution, is permeable to oxygen, and is capable of adjusting itself and maintains contact close to the skin. In this way, considering all the properties evaluated, the optimized film has characteristics suitable for biomedical applications as wound dressings.

Gelatin-based films containing clinoptilolite-Ag for application as wound dressing.

Dressings used in burns and chronic wounds treatment must present antimicrobial characteristics. Silver-based compounds are used for a long time as antiseptics, but they present problems related to the release of silver. In order to control the release, Ag+ ions may be immobilized in supports that must be dispersed in the film used as wound dressing. In this work gelatin-based films using glycerol as plasticizer and incorporated with different concentrations of clinoptilolite zeolite impregnated with silver ions were prepared and characterized, and the potential antimicrobial activity was investigated. For this purpose, films were produced by casting and evaluated in relation to their mechanical, chemical, thermal, morphological and antimicrobial properties, in addition the amount of silver present in the films was quantified and the kinetics of Ag+ release in vitro was studied. The antimicrobial analysis was done qualitatively, using Escherichia coli and Staphylococcus aureus bacteria and the microorganisms commonly present on human skin collected with a swab, and quantitatively, using Escherichia coli and Staphylococcus aureus. Characterization tests demonstrated that the glycerol concentration of 25% and the zeolite concentration of 0.5% resulted in films with more suitable properties for wound dressing applications and the silver release test showed that the release of the active compound occurs slowly, as expected. All gelatin/clinoptilolite-Ag films showed antibacterial activity against Staphylococcus aureus and human skin bacteria, not presenting expressive differences on the size of the formed halo. Moreover, by the quantitative antimicrobial analisys, it was observed that as the glycerol concentration increases, the antimicrobial action was faster and at the end of the experiment, there were no S. aureus in the solutions where the films were immersed and for the assay with E. coli, the bactericidal activity is slower and probably is needed a higher concentration of silver ions in the sample to completely inhibit the bacteria. However, the bactericidal activity of the gelatin/clinoptilolite-Ag films was satisfactory due its effectiveness in reducing bacterial growth of E. coli and S. aureus. Based on these results the prepared gelatin/clinoptilolite-Ag films could serve as a promising wound dressing with great antibacterial properties, thus possibly helping also the wound healing.