Modelling Chemical Kinetics of Soybean Oil Transesterification Process for Biodiesel Production: An Analysis of Molar Ratio between Alcohol and Soybean Oil Temperature Changes on the Process Conversion Rate

A mathematical model describing chemical kinetics of transesterification of soybean oil for biodiesel production has been developed. The model is based on the reverse mechanism of transesterification reactions and describes dynamics concentration changes of triglycerides, diglycerides, monoglycerides, biodiesel, and glycerol production. Reaction rate constants were written in the Arrhenius form. An analysis of key process variables such as temperature and molar ratio soybean oil- alcohol using response surface analysis was performed to achieve the maximum soybean conversion rate to biodiesel. The predictive power of the developed model was checked for the very wide range of operational conditions and parameters values by fitting different experimental results for homogeneous catalytic and non-catalytic processes published in the literature. A very good correlation between model simulations and experimental data was observed

Biosorption of the Copper and Cadmium Ions - a Study through Adsorption Isotherms Analysis

In this work, the biosorption process of copper-cadmium ions binary mixture by using marine algae Sargassum filipendula was investigated. A set of experiments was performed to obtain equilibrium data for the given batch operational conditions - T=30°C, pH=5. The interpretation of equilibrium data was based on the binary adsorption isotherms models in the Langmuir and Freundlich forms. To evaluate the models parameters, nonlinear identification procedure was used based on the Least Square statistical method and SIMPLEX local optimizer. An analysis of the obtained results showed that the marine algae biomass has higher affinity to copper ions than to cadmium ones. The biomass maximum adsorption capacity for the binary system was about 1.16 meq/g

Biosorption of BF-4B Reactive Red Dye by using Leaves of Macrophytes Eichhornia crassipes

The removal potential on BF-4B reactive red dye by Eichhornia crassipes dried leaves has been investigated. Furthermore, the influence of process parameters such as solution pH, agitation, and particle size on the dye adsorption efficiency was assessed. Both kinetic and equilibrium experiments were performed in batch operation of the system. Kinetic results demonstrated that the equilibrium state was achieved after 45 min process time. The kinetic experimental data were best described by applying a pseudo-second order model that evaluated the value of rate constant 0.22 g/mg/min and an equilibrium dye concentration 8.20 mg/g. A set of isotherm models, taken from knowledge database, was tested in order to represent the equilibrium adsorption data. The Langmuir model performed the best when fitting experimental data where the maximum adsorption capacity of 20.38 mg/g was achieved. The results demonstrated that the E. crassipes has good potential to be used as a biosorbent in industrial treatment systems to remove reactive dyes from textile effluents

Cr(VI) reduction by activated carbon and non-living macrophytes roots as assessed by Kβ spectroscopy

In this work, the behavior of cationic-exchange resin, activated carbon, and non-living aquatic macrophytes biomasses on the Cr(VI) and Cr(III) uptake and Cr(VI) reduction was investigated. The high-resolution X-ray fluorescence (HR-XRF) technique was used to study the adsorption process, as well as to study Cr(VI) reduction and removal from metal solutions. Batch Cr ions sorption experiments at pH 3.5 were carried out in order to speciate 3d-transition metal onto the surface of these types of adsorbents by a Kβ spectra analysis. Cr-Kβ satellite lines have been characterized for all Kβ spectra of Cr ions onto treated samples and reference material. Based on their energy position and intensity of Cr-Kβ satellite lines as well as their related to reference material shift energy, activated carbon and non-living aquatic macrophytes roots were found to act mainly as good adsorbents, first reducing Cr(VI) to Cr(III) and then followed by a Cr(III) adsorption. Although cationic-exchange resin was treated with Cr(VI) solution, no evidence of any Cr-Kβ spectral satellite lines was shown in it, suggesting that Cr(VI) was not removed in a cationic-exchange process. Evidence of reduction of hexavalent chromium by adsorbent materials was assessed by Kβ spectral lines analysis.Fil: Módenes, Aparecido N.. Universidade Estadual Do Oeste Do Pará; BrasilFil: Espinoza Quiñones, Fernando R.. Universidade Estadual Do Oeste Do Pará; BrasilFil: Palácio, Soraya M.. Universidade Estadual Do Oeste Do Pará; BrasilFil: Kroumov, Alexander D.. University of Kentucky; Estados UnidosFil: Stutz, Guillermo Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; ArgentinaFil: Tirao, German Alfredo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; ArgentinaFil: Camera, Adriana S.. Universidade Estadual Do Oeste Do Pará; Brasi

Travel burden and clinical presentation of retinoblastoma: analysis of 1024 patients from 43 African countries and 518 patients from 40 European countries

BACKGROUND: The travel distance from home to a treatment centre, which may impact the stage at diagnosis, has not been investigated for retinoblastoma, the most common childhood eye cancer. We aimed to investigate the travel burden and its impact on clinical presentation in a large sample of patients with retinoblastoma from Africa and Europe. METHODS: A cross-sectional analysis including 518 treatment-naïve patients with retinoblastoma residing in 40 European countries and 1024 treatment-naïve patients with retinoblastoma residing in 43 African countries. RESULTS: Capture rate was 42.2% of expected patients from Africa and 108.8% from Europe. African patients were older (95% CI -12.4 to -5.4, p<0.001), had fewer cases of familial retinoblastoma (95% CI 2.0 to 5.3, p<0.001) and presented with more advanced disease (95% CI 6.0 to 9.8, p<0.001); 43.4% and 15.4% of Africans had extraocular retinoblastoma and distant metastasis at the time of diagnosis, respectively, compared to 2.9% and 1.0% of the Europeans. To reach a retinoblastoma centre, European patients travelled 421.8 km compared to Africans who travelled 185.7 km (p<0.001). On regression analysis, lower-national income level, African residence and older age (p<0.001), but not travel distance (p=0.19), were risk factors for advanced disease. CONCLUSIONS: Fewer than half the expected number of patients with retinoblastoma presented to African referral centres in 2017, suggesting poor awareness or other barriers to access. Despite the relatively shorter distance travelled by African patients, they presented with later-stage disease. Health education about retinoblastoma is needed for carers and health workers in Africa in order to increase capture rate and promote early referral

Desenvolvimento de um modelo da cinética enzimática da transesterificação de óleos vegetais para produção de biodiesel = Development of the enzymatic kinetics model of vegetable oils transesterification for biodiesel production

Atualmente, a tecnologia de produção enzimática do biodiesel é mais uma alternativa em relação aos métodos químicos que utilizam catalisadores ácidos ou básicos. A enzima lipase utilizada como catalisador desse processo pode ser obtida de microrganismoscomo Pseudomonas fluorescens, P. cepacia, Candida antarctica, dentre outros. Neste trabalho, propomos um mecanismo da transesterificação de triglicerídeos catalisada por enzima lipase. O processo foi formalizado em três reações consecutivas, nas quais são formados osdiglicerídeos e monoglicerídeos. Outras três etapas intermediárias das reações envolvendo a lipase foram consideradas. A identificação dos parâmetros do modelo desenvolvido foi feita para condições reacionais em que a alimentação é feita na proporção estequiométrica dos reagentes. O modelo desenvolvido foi testado com dados experimentais em diversas condições operacionais encontradas na literatura. Os resultados das simulações mostram boa flexibilidade do modelo, ajustando os dados em várias condições de transesterificaçãoenzimática para produção de biodiesel.Currently the technology of enzymatic production of biodiesel is more promising than that based on chemical methods, using acidic orbasic catalysts. The enzyme lipase used as catalyst in this process can be isolated from microorganisms such as Pseudomonas fluorescens, P. cepacia, Candida antarctica among others. In this work, a mechanism for the transesterification of triglycerides catalyzed by lipase for production of biodiesel is proposed. The process was modeled in three consecutive reactions where diglycerides and monoglycerides were formed. Other three intermediate stages involving lipase were considered. The identification of parameters with the developed model was performed for reaction conditions where stoichiometric amount of reagents were used. The developed modelwas tested for different operational conditions with experimental data found in the literature. The simulation results showed good model flexibility

Modeling Biodegradation Kinetics on Benzene and Toluene and Their Mixture

The objective of this work was to model the biodegradation kinetics of toxic compounds toluene and benzene as pure substrates and in a mixture. As a control, Monod and Andrews models were used. To predict substrates interactions, more sophisticated models of inhibition and competition, and SKIP (sum kinetics interactions parameters) model were applied. The models evaluation was performed based on the experimental data from Pseudomonas putida F1 activities published in the literature. In parameter identification procedure, the global method of particle swarm optimization (PSO) was applied. The simulation results show that the better description of the biodegradation process of pure toxic substrate can be achieved by Andrews' model. The biodegradation process of a mixture of toxic substrates is modeled the best when modified competitive inhibition and SKIP models are used. The developed software can be used as a toolbox of a kinetics model catalogue of industrial wastewater treatment for process design and optimization

<b>Desenvolvimento de um modelo da cinética enzimática da transesterificação de óleos vegetais para produção de biodiesel</b> - DOI: 10.4025/actascitechnol.v29i1.79

Atualmente, a tecnologia de produção enzimática do biodiesel é mais uma alternativa em relação aos métodos químicos que utilizam catalisadores ácidos ou básicos. A enzima lipase utilizada como catalisador desse processo pode ser obtida de microrganismos como <em>Pseudomonas fluorescens, P. cepacia, Candida antarctica</em>, dentre outros. Neste trabalho, propomos um mecanismo da transesterificação de triglicerídeos catalisada por enzima lipase. O processo foi formalizado em três reações consecutivas, nas quais são formados os diglicerídeos e monoglicerídeos. Outras três etapas intermediárias das reações envolvendo a lipase foram consideradas. A identificação dos parâmetros do modelo desenvolvido foi feita para condições reacionais em que a alimentação é feita na proporção estequiométrica dos reagentes. O modelo desenvolvido foi testado com dados experimentais em diversas condições operacionais encontradas na literatura. Os resultados das simulações mostram boa flexibilidade do modelo, ajustando os dados em várias condições de transesterificação enzimática para produção de biodiesel

Advantageous Combinations of Nanoencapsulated Oregano Oil with Selected Antibiotics for Skin Treatment

The aim of the present study was to evaluate the antimicrobial activity of combinations between encapsulated oregano oil and the most commonly applied antibiotics (ciprofloxacin or gentamicin) against skin infections. In particular, chitosan-alginate nanoparticles loaded with oregano oil and the selected antibiotics were included in methylcellulose hydrogels. Consistency, spreadability, pH of the hydrogel and in vitro release rate of the oil were considered appropriate for topical application. The combination of encapsulated oil and gentamicin in the hydrogel resulted in a synergistic effect against methicillin-sensitive (MSSA) and methicillin-resistant (MRSA) Staphylococcus aureus strains. It was expressed in a fourfold reduction in the effective concentration of gentamicin and 98% inhibition of the bacterial metabolic activity. When ciprofloxacin was included in the combination instead of gentamicin, an additive effect with a two-fold decrease in the effective drug concentration and a 96% reduction in the bacterial metabolic activity were observed. Both combinations significantly inhibited the formation of MRSA biofilm by more than 90% when applied. In vivo application of the hydrogel containing the synergistic combination between the encapsulated oil and gentamicin did not induce irritation of the rabbit skin

New Insights in Routine Procedure for Mathematical Evaluation of in vitro Cytotoxicity Data from Cancer Cell Lines

In oncopharmacology, the common procedure to evaluate median-effect concentrations (IC50) on experimental data is based on the use of well-established kinetic models representing inhibition effects of drugs on human cancer cell lines. Several widespread software programs, such as GraphPad Prism and CompuSyn offer possibilities for calculation of IC50 through the model of Chou. In recent study, we analyzed the results from those two software programs and compared them with the non-linear programming procedure written by us in the MAPLE symbolic software. The last evaluated IC50 more precisely and the correlation coefficient R value was better in all trails. We demonstrated the efficiency of non-linear programming procedures in examples of two cancer cell lines treated with three different drugs. The response surface analysis showed the potential of the applied kinetic model. As a result, we were able to define better the IC50 values and to use them in planning further experiments in human cancer cell lines related to single drug influence and drug-drug interference