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.

Ampicillin removal by adsorption onto activated carbon: kinetics, equilibrium and thermodynamics.

Pharmaceutical compounds are essential to preserve human and animal welfare, as well as to prevent illnesses. However, the elevated consumption of drugs, followed by incorrect disposal and inefficient wastewater treatment, may increase their environmental risk. In the case of antibiotics, such as ampicillin, some of the already known consequences are bacterial resistance and some toxic interactions with aquatic organisms. The scope of the present work is to investigate the removal of ampicillin through batch adsorption experiments onto granular activated carbon (GAC). The influence of pH and phase contact time were evaluated. Pseudo-first order, pseudo-second order and intraparticle diffusion models were adjusted to experimental data to determine process kinetics. In order to study adsorption equilibrium and thermodynamics parameters, isotherms at 298 K, 298 K and 308 K were constructed. The models of Langmuir, Freundlich and Sips fitted to experimental data. The best results (73% of removal, residual concentration 5.2 mg L-1) were reached at pH 6 and 120 minutes of contact time. Pseudo-first order model better represented the adsorption kinetics (R2 = 0.99), while the Langmuir equation suited well the experimental isotherms at 288 K and 298 K (R2 = 0.998 and R2 = 0.991) and the Sips equation better represented the system at 308 K (R2 = 0.990). Thermodynamic parameters were estimated as ΔG° = -6,000 J mol-1; -6,700 J mol-1; -7,500 J mol-1 at 288 K, 298 K and 308 K respectively, ΔH° = 14,500 J mol-1 and ΔS° = 71.0 J mol-1 K-1. The results indicate that this process is spontaneous, efficient and potentially applicable in the removal of ampicillin from water.

Potassic zeolites from Brazilian coal ash for use as a fertilizer in agriculture.

Brazilian coal has an ash content ranging from 30 to 50% by weight. Consequently, its use in coal-fired thermoelectric for power production generates a lot of waste. The construction sector is the largest consumer of coal ash, but it cannot absorb the entire amount generated. Thus, other applications for coal ash should be studied in aim to optimize the use of this industrial waste. This research had as focus to synthesize potassic zeolite from of the coal ash into on potassium fertilizer for the grown wheat plant. In this work, it was used a subbituminous coal from Mina do Leão (RS, Brazil) presenting 48.7% ash content on a dry basis. Concerning the synthesis of potassic zeolite, it was adopted the conventional method of hydrothermal treatment with potassium hydroxide. A schedule of experiments was conducted in order to define the optimum condition of zeolite synthesis that was then used an alkaline solution of 5M KOH with a reaction time of 24h at 150°C. According to this procedure, it was obtained a zeolite with a single crystalline phase, identified through X-ray diffraction as Merlinoite. Subsequently, it was performed a set of tests using potassic zeolite asa fertilizer for plants in a greenhouse. The synthesized potassic zeolite showed a good potential for its use as fertilizer in agriculture.

Critical velocity, anaerobic distance capacity, maximal instantaneous velocity and aerobic inertia in sprint and endurance young swimmers.

Critical velocity (CV), anaerobic distance capacity (ADC), maximal instantaneous velocity (V (max)), and aerobic inertia (tau) were calculated from two (CV(2par) and ADC(2par)), three (CV(3par), ADC(3par), and V (max 3par)), and four-parameter model data (CV(4par), ADC(4par), V (max 4par), and tau), which were obtained from six different times and distances (50, 100, 200, 400, 800, and 1,500 m) swum in front crawl stroke under maximal intensity. Fourteen swimmers (14-15-year-old; sprint and endurance groups, each group n = 7) volunteered in this study. CV values were not influenced by the groups. The model effects showed that CV(2par) was higher than CV(3par) and CV(4par) regardless of the group used. In addition, CV(3par) and CV(4par) were similar. ADC seems to be better estimated using both three- and four-parameter models. V (max) was higher in the sprint group regardless of the model used. The models effects showed that the V (max 4par) was higher than the V (max 3par) regardless of the group. Sprint and endurance groups showed similar tau values. The analysis of the models (F test, coefficient of determination R (2), and adjusted coefficient of determination R (adjusted) (2) ) showed that the three-parameter model was more appropriate among the applied models. Although the four-parameter model showed better correlation for the endurance group, the inclusion of tau (fourth parameter) did not significantly improve the quality of adjustment. However, it is important to emphasize the availability of another parameter for the study of bioenergetics in swimming and other sports.

Production of basic chromium sulfate by using recovered chromium from ashes of thermally treated leather.

Leather wastes tanned with chromium are generated during the production process of leather, hence the wastes from hand crafted goods and footwear industries are a serious environmental problem. The thermal treatment of leather wastes can be one of the treatment options because the wastes are rich in chromium and can be used as a raw material for sodium chromate production and further to obtain several chromium compounds. The objective of this study was to utilize the chromium from leather wastes via basic chromium sulfate production to be subsequently applied in a hide tanning. The obtained results have shown that this is the first successful attempt to achieve desired base properties of the product. The result was achieved when the following conditions were applied: a molar ratio between sodium sulfite and sodium dichromate equal to 6; reaction time equal to 5 min before addition of sulfuric acid; pH of sodium dichromate solution equal to 2. Summarizing, there is an opportunity to utilize the dangerous wastes and reused them in the production scheme by minimizing or annulling the environmental impact and to attend a sustainable process development concept.

Formation of PCDD and PCDF in the thermal treatment of footwear leather wastes.

The leather waste generated by the footwear industry is considered dangerous due to the presence of trivalent chromium, derived from the salt utilized to tan hides. In Brazil, the majority of this waste is disposed on landfills and only about 3% are recycled. The thermal treatment is an alternative method for purification of such residues. By using this technique it is possible to generate energy and recover the chromium present in the ash for the production of basic chromium sulfate (tanning industry), high carbon ferrochromium or carbon-free ferrochromium (steel industry). In the last 10 years, the gasification and combustion of footwear leather waste have been intensively studied at the Federal University of Rio Grande do Sul. The research experiment for characterization of the emissions of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) were carried out in a semi-pilot unit (350 kW(th)). From new investments the thermal capacity of the unit will increase to 600 kW(th). The unit will produce power from the heat generated in the combustion. The experimental results indicated that during the thermal treatment of footwear leather wastes, the formation mechanism of PCDD/F is the de novo synthesis. Most of PCDD/F were found in the particulate phase (>95%). A kinetic model was used for discussion of the achieved experimental results. The model is based in the carbon gasification, PCDD/F formation, desorption and degradation. From the conclusions obtained in this work will be possible minimize the PCDD/F formation in process of combustion of footwear leather wastes.