Eliane Bezerra Cavalcanti

Estudo do equilíbrio e cinética da biossorção do pb2+ por saccharomyces cerevisiae

The biosorption, based on the use of biomass for removal of ions is distinguished as an innovative and promising technology when compared with the traditional methods. In this context, the aim of the present work is to use Saccharomyces cerevisiae as biosorbent for the retention of Pb2+ metal ions. Factorial design was used for evaluation of the process. The observed equilibrium data were well described by Langmuir and Freundlich adsorption isotherms. The maximum adsorption capacity was 1486.88 mg/g. The results indicated that Saccharomyces cerevisiae is suitable for biosorption of Pb2+ metal ions.

Tratamentos dos efluentes gerados na produção de biodiesel

The wastewaters from biodiesel production contain as primarily wastes sodium or potassium soaps, fatty acids, glycerin, alcohol and other contaminants. In general, these waters are chemically unsuitable for release to any water body, so, it is necessary the adoption of techniques for the treatment of this effluent. In this review, electrochemical, biological, physicochemical, and combined treatments reported for the removal of the wastewater containing pollutants come from biodiesel production have been summarized. In addition, the recovery, the reuse, the energy production and the synthesis of new compounds from the organic matter contained in this kind of effluent are also reviewed.

Characterization of a tubular electrochemical reactor for the degradation of the commercial diuron herbicide

ABSTRACT After designing and constructing an electrochemical reactor with concentric electrodes and tangential feed (RECT), it is necessary to characterize it and to study its performance. The experimental study of the residence time distribution (RTD) was conducted for flow rates of 2.78 × 10–6 m3 s–1, 8.33 × 10–6 m3 s–1 and 13.9 × 10–6 m3 s–1. According to the values obtained from the Pe number (0.67–1.52), the RECT fits as tubular with great dispersion. The determined empirical correlation (Sh = 18.16 Re0.50 Sc0.33) showed a laminar flow behavior in the range of Reynolds number (Re) between 23 and 117. In order to use RECT in effluent treatment, an electrochemical oxidation study of the Diuron model molecule (Nortox®) was performed to analyze reactor performance in a closed system with total reflux. A decay kinetics of pseudo-first order was associated with the decay of the concentration of diuron and 30% mineralization in 180 min of process were obtained, having a total volume of 4 × 10–3 m3 and an initial concentration of commercial Diuron in 215.83 mg dm–3. Eleven by-products were identified by HPLC–MS analysis and, from this, it was possible to propose a route of degradation of the diuron. From these observations, it can be inferred that the studied electrochemical reactor had applicability in the degradation of recalcitrant compounds, as is the case of commercial diuron. Make some changes in the electrochemical reactor studied and other advanced oxidative processes, such as electro-Fenton, can be associated with the studied system to achieve a better conversion efficiency. GRAPHICAL ABSTRACT

Synthesis of high-area chemically modified electrodes using microwave heating

Abstract The synthesis of dimensionally stable carbon-based chemically modified electrodes (CMEs) is a challenge. The synthesis method, the electrode composition, and the heating used influences various properties of the electrodes. Here, we show an innovative, low cost, and efficient heating method for the CMEs production. We deposited ternary ruthenium, antimony, and tantalum or bismuth oxides on carbon-felts by the Pechini method focusing on the influence of different heating methods (conventional and microwave) on their electrochemical and physical properties. The oxides synthesized using microwave heating coated completely the carbon-felts fibers, displaying homogeneous morphology, while maintaining their three-dimensional character. XRD and XRF analyses confirm the presence of the desired oxides on the coating surfaces and the experimental metal load values close to the nominal (87–91% for Ru, 3–6% for Sb, and 4–7% for Ta or Bi, respectively). The microwave-assisted method yields CMEs with electrochemical active areas 136-fold (for tantalum-based) and 153-fold (for bismuth-based) higher than the unmodified carbon felt. The service lifetime of the CMEs is almost twice as high when using microwave heating than when using conventional heating, which is attributed to the complete and homogeneous coating of the fibers obtained using this heating method. In contrast, the conventional heating led to the incomplete covering of the fibers and to CMEs with low stability. Therefore, the use of microwave heating for the CMEs synthesis reduces the production time at around 60%, thus decreasing the production costs and producing CMEs with improved quality and stability when compared to both conventional-made CMEs and unmodified electrodes.

High-Area Ti/Pt Electrodes for the Electrochemically Catalyzed Transesterification of Soybean Oil with Methanol

Biodiesel fuel is a renewable energy source normally produced in industry by using an alkaline homogeneous catalyst to promote the transesterification of oil and methanol to fatty acid methyl ester (FAME). Undesirable side reactions occur when poorly refined oils are used, leading to serious problems of product separation and low FAME yield. Therefore, about 85% of the cost of biodiesel is determined by the cost of the feedstock. Here, we describe the development of high-area Pt films deposited on Ti substrates for the electrolytic synthesis of biodiesel from soybean oil containing water, without the addition of catalyst. The higher both the calcination temperature and the number of layers deposited on the Ti surface, the higher the electrochemically active area of Pt exposed to surface. Conversion into esters in electrolysis is proportional to the increase in the superficial area of the Ti/Pt electrodes. Thus, it is possible to synthesize biodiesel using electrodes containing very low amounts of Pt (<0.441 mg cm−2), an important parameter in the industrial production of biodiesel.