No abstract

No abstract

Malaria is a principal cause of illness and death in countries where the disease is endemic. Personal protection against mosquitoes using repellents could be a useful method that can reduce and/or prevent transmission of mosquito-borne diseases. The available repellent products, such as creams, roll-ons, and sprays for personal protection against mosquitoes, lack adequate long-term efficacy. In most cases, they need to be re-applied or replaced frequently. The encapsulation and release of the repellents from several matrices has risen as an alternative process for the development of invention of repellent based systems. The present work reviews various studies about the development and use of repellent controlled-release formulations such as polymer microcapsules, polymer microporous formulations, polymer micelles, nanoemulsions, solid-lipid nanoparticles, liposomes and cyclodextrins as new tools for mosquito-borne malaria control in the outdoor environment. Furthermore, investigation on the mathematical modelling used for the release rate of repellents is discussed in depth by exploring the Higuchi, Korsmeyer-Peppas, Weibull models, as well as the recently developed Mapossa model. Therefore, the studies searched suggest that the final repellents based-product should not only be effective against mosquito vectors of malaria parasites, but also reduce the biting frequency of other mosquitoes transmitting diseases, such as dengue fever, chikungunya, yellow fever and Zika virus. In this way, they will contribute to the improvement in overall public health and social well-being.

RESUMOAs nanoferritas mistas de Ni 0,5 Zn 0,5 Fe 2 O 4 e Ni 0,2 Cu 0,3 Zn 0,5 Fe 2 O 4 foram sintetizadas por reação de combustão usando ureia como combustível e um reator cônico como fonte de aquecimento para produção em bateladas de 10 g, e então, testadas como nanocatalisadores heterogêneos nas reações de transesterificação e esterificação metílica e etílica do óleo de soja para produção de biodiesel. Durante as sínteses foram registrados o tempo e a temperatura das reações, bem como observadas a liberação de gases e a cor das chamas emitidas. As amostras foram caracterizadas por DRX, EDX, FTIR, MEV/EDS, BET e cromatografia gasosa. Os testes reacionais foram executados para 10 g do óleo em duração de 1 h, razão molar 1:12 óleo:álcool, 2 % (m/m) de catalisador e conduzidas a 180 ºC. Os difratogramas de DRX e os espectros de FTIR revelaram presença da fase espinélio inverso tipo B(AB) 2 O 4 . A morfologia apresentou a formação de aglomerados de aspecto frágil e elevada área de superfície. As análises cromatográficas produziram excelentes resultados nas reações de esterificação para ambas amostras nas condições testadas, com destaque especial para Ni 0,5 Zn 0,5 Fe 2 O 4 , cujas conversões foram de 91,4 % em ésteres metílicos e de 77,8 % em ésteres etílicos, enquanto que a amostra Ni 0,2 Cu 0,3 Zn 0,5 Fe 2 O 4 apresentou conversões de 75,1 e 65,1 %, respectivamente. As conversões na transesterificação metílica e etílica foram de 14 e 2 % para Ni 0,5 Zn 0,5 Fe 2 O 4 e de 11 e 3 % para Ni 0,2 Cu 0,3 Zn 0,5 Fe 2 O 4 .Palavras-Chave: Ferritas mistas, reação de combustão, nanocatalisadores, transesterificação, esterificação, biodiesel. ABSTRACTThe mixed nanoferrites of Ni 0.5 Zn 0.5 Fe 2 O 4 and Ni 0.2 Cu 0.3 Zn 0.5 Fe 2 O 4 were synthesized by combustion reaction using urea as fuel and a conical reactor as heating source in batches of 10 g, and then tested as heterogeneous nanocatalysts in the transesterification and esterification reaction of soya bean oil using the methyl and ethyl routes to biodiesel production. During the synthesis the time and temperature of the reactions were measured, and the evolved gases and the color of the emitted flames were observed. The samples were characterized by XRD, EDX, FTIR, SEM/EDS, BET and gas chromatography. The reaction tests were carried out with 10 g of oil for 1 h, oil:alcohol molar ratio of 1:12, 2 % (w/w) of catalyst, and conducted at 180 °C. The XRD patterns and the FTIR spectra revealed the presence of the inverse spinel phase type B(AB) 2 O 4 . The morphology showed the formation of agglomerates with fragile morphology and high surface area. The chromatographic analysis produced excellent results in the esterification reactions for both samples in the tested conditions, with special emphasis on Ni 0.5 Zn 0.5 Fe 2 O 4 , whose conversions were of 91.4 % in methyl esters and of 77.8 % in ethyl esters, while the Ni 0.2 Cu 0.3 Zn 0.5 Fe 2 O 4 sample showed conversion of 75.1 and 65.1 %, respectively.

BACKGROUND The effectiveness of mosquito repellents, whether applied topically on the skin or released from a wearable device, is determined by the evaporation rate. This is because a repellent has to be present in the form of a vapour in the vicinity of the exposed skin that needs protection. Therefore, gravimetric techniques were used to investigate the direct evaporation of selected liquid repellents, their permeation through polymer films, and their release from a microporous polyethylene matrix. RESULTS Evaporation of a repellent into quiescent air is determined by its air permeability. This is a product of the vapour pressure and the diffusion coefficient, i.e. SA=PAitalicsatDA. It was found that repellents could be ranked in terms of decreasing volatility as: ethyl anthranilate > citriodiol > dimethyl phthalate > N,N‐diethyl‐meta‐toluamide (DEET) > decanoic acid > ethyl butylacetylaminopropionate > Icaridin. Experimental SA values, at 50 °C, ranged from 0.015 ± 0.008 mPa m2 s−1 for the least volatile repellent (Icaridin) to 0.838 ± 0.077 mPa m2 s−1 for the most volatile (ethyl anthranilate). The release rate from microporous polyethylene strands, produced by extrusion‐compounding into ice water baths followed a similar ranking. These strands featured an integral skin‐like membrane that covered the extruded strands and controlled the release of the repellent at a low effective rate. CONCLUSION The high thermal and thermo‐oxidative stability together with the low volatility of the mosquito repellents ethyl butylacetylaminopropionate and Icaridin make them attractive candidates for long‐lasting wearable mosquito‐repellent devices. Such anklets/bracelets may have utility for outdoor protection against infective mosquito bites in malaria‐endemic regions. © 2019 Society of Chemical Industry

No abstract

Summary Biodiesel was successfully produced by transesterification process of soybean oil and methanol using Ni0.5Zn0.5Fe2O4 nanomagnetic catalyst. The Ni0.5Zn0.5Fe2O4 catalyst was synthesized by the combustion method and its properties were investigated using X‐ray diffraction, N2 physisorption at 77 K, Fourier transform infrared analysis, thermogravimetric analysis, scanning electron microscopy, and a transmission electron microscopy. The performance of catalyst was investigated during transesterification reaction for fatty acid methyl esters (FAMEs) production. FAMEs were studied by gas chromatography technique. The effect of reaction conditions such as molar ratio of methanol/soybean oil, catalyst amount, reaction temperature, and reaction time on FAMEs yield was also evaluated. The biodiesel yield of 92.1% was obtained under the following reaction conditions: 9:1 of methanol/soybean oil molar ratio and, 2% of catalyst loading at 180°C in 3 hours. Furthermore, the energy of activation (Ea) was 67.4 kJ.mo1−1 and the pre‐exponential factor (ko) was 8.35 × 104 L mol−1 min−1 determined using Arrhenius equation.

Heterogeneous photocatalysis using titanium dioxide (TiO2) and zinc oxide (ZnO) has been widely studied in various applications, including organic pollutant remediation in aqueous systems. The popularity of these materials is based on their high photocatalytic activity, strong photosensitivity, and relatively low cost. However, their commercial application has been limited by their wide bandgaps, inability to absorb visible light, fast electron/hole recombination, and limited recyclability since the nanomaterial is difficult to recover. Researchers have developed several strategies to overcome these limitations. Chief amongst these is the coupling of different semi-conductor materials to produce heterojunction nanocomposite materials, which are both visible-light-active and easily recoverable. This review focuses on the advances made in the development of magnetic ferrite-based titanium oxide and zinc oxide nanocomposites. The physical and magnetic properties of the most widely used ferrite compounds are discussed. The spinel structured material had superior catalytic and magnetic performance when coupled to TiO2 and ZnO. An assessment of the range of synthesis methods is also presented. A comprehensive review of the photocatalytic degradation of various priority organic pollutants using the ferrite-based nanocomposites revealed that degradation efficiency and magnetic recovery potential are dependent on factors such as the chemical composition of the heterojunction material, synthesis method, irradiation source, and structure of pollutant. It should be noted that very few studies have gone beyond the degradation efficiency studies. Very little information is available on the extent of mineralization and the subsequent formation of intermediate compounds when these composite catalysts are used. Additionally, potential degradation mechanisms have not been adequately reported.