Michele S.P. Enders

Intensification of ultrasonic-assisted crude oil demulsification based on acoustic field distribution data

Water removal is an essential step during crude oil production due to several problems such as increased transportation costs and high corrosion rate due to dissolved salts. Indirect low frequency ultrasonic energy (US), using baths, has been recently proposed as an effective alternative for crude oil demulsification. However, the reactor position during sonication and its influence on the demulsification efficiency for crude oil has not been evaluated. In this sense, the aim of this study was to develop an automated system based on an open source hardware for mapping the acoustic field distribution in an US bath operating at 35kHz using a hydrophone. Data acquired with this system provided information to evaluate the demulsification efficiency in the different positions of the US bath and correlate it with the acoustic intensity distribution. The automated 3D-mapping system revealed a higher acoustic intensity in the regions immediately above the transducers (ca. 0.6Wcm-2), while the other regions presented a relatively lower intensity (ca. 0.1Wcm-2). Experimental data demonstrated that reactors positioned in the most intense acoustic regions provided a much higher efficiency of demulsification in comparison with the ones positioned in the less intense acoustic field regions. Demulsification efficiency up to 93% was obtained with 15min of sonication (100% amplitude) using few amount of chemical demulsifier. Hence, this work demonstrated that the information acquired with the developed mapping system could be used for inducing a higher efficiency of demulsification only by finding the more suitable position of reactor in the US bath, which certainly will help development of appropriate reactors design when looking for such approach.

Determination of Br, Cl and I in honey using ICP-based techniques following microwave-assisted wet digestion with alkaline H2O2 in a single reaction chamber

In this work, a sample preparation method using only H2O2 in an alkaline medium in a single reaction chamber system (SRC-UltraWave™) was evaluated for honey digestion and for further determination of Br, Cl and I by inductively coupled plasma (ICP)-based techniques. Some important parameters, such as temperature, volume of H2O2, sample mass and volume of NH4OH, were evaluated to produce digests with the minimum concentration of residual carbon (RC). Determination of RC and Cl was carried out using inductively coupled plasma optical emission spectrometry (ICP-OES), while Br and I were determined by inductively coupled plasma mass spectrometry (ICP-MS). Digestion was performed using up to 500 mg of honey, 8 mL of H2O2, 500 μL of NH4OH and a maximum temperature and pressure of 270 °C and 199 bar, respectively. The digests obtained by the proposed method presented a concentration of RC lower than 220 mg L−1 combined with an alkaline pH that minimized memory effects during ICP-based technique analysis. The accuracy of the proposed method was evaluated by analysis of certified reference materials NIST 8433 (corn bran) and NIST 1568a (rice flour), and by comparison between the results obtained using the proposed method and those obtained by microwave-induced combustion (MIC). Significant differences were not observed on comparing the results of the proposed method with reference values of CRMs and MIC. Limits of detection obtained by the proposed method were 10 μg g−1 for Cl using ICP-OES and 0.03 and 0.005 μg g−1 for Br and I (ICP-MS), respectively.

Response surface methodology approach for the optimization of tartrazine removal by heterogeneous photo-Fenton process using mesostructured Fe2O3-suppoted ZSM-5 prepared by chitin-templating

ABSTRACT A statistical optimization of tartrazine dye removal process from aqueous solution by heterogeneous photo–Fenton process using Fe2O3-supported ZSM-5 catalyst was performed. ZSM-5 support was prepared by chitin-templating technique to obtain a mesoporous structure. Thereafter, Fe2O3 was supported on ZSM-5 through wet impregnation method. This material was characterized by different techniques and posteriorly evaluated as a catalyst for the removal of tartrazine from aqueous solution. A central composite rotational design coupled with response surface methodology approach was used to evaluate the influence of different reaction conditions on the decolorization of a solution containing tartrazine and to obtain the optimum conditions. Under the optimum experimental conditions of dye decolorization, a mineralization experiment was conducted through analysis of total organic carbon. In these conditions, 95% of decolorization was achieved at 30 min of reaction and a significant mineralization of 80% was observed at 180 min. Therefore, the photo-Fenton process using Fe2O3-supported ZSM-5 prepared by chitin-templating was proved to be feasible for both the decolorization and mineralization of tartrazine in aqueous solution.

An in situ pre-concentration method for fluorine determination based on successive digestions by microwave-induced combustion

A new strategy based on successive digestions by microwave-induced combustion (MIC) in the same reaction vessel with a single absorbing solution was proposed. As a proof of concept, F was determined by ion-selective electrode (ISE) in seafood digests. Samples were pressed as pellets (up to 0.7 g) and combusted in closed quartz vessels pressurized with oxygen. Sequential digestions were each performed (up to 4 combustion cycles) in the same vessel and using the same absorbing solution. In each cycle, a new filter paper, igniter and sample pellet (0.7 g of sample) were used. Ammonium hydroxide solutions (10-100 mmol L-1) were evaluated for F absorption. Accuracy of the proposed method was evaluated using certified reference material of oyster tissue (NIST 1566a) and also by comparison of results after pyrohydrolysis method. Up to 3 digestion cycles (total mass of 2.1 g) could be used with 50 mmol L-1 NH4OH as absorbing solution. Results were in agreement with those obtained using pyrohydrolysis and also with certified reference value; the coefficient of variation after 3 cycles was below 5%, which was considered as suitable for F determination even at low concentration. The residual carbon in digests was lower than 25 mg L-1, allowing F determination by ISE virtually free of interferences due to dissolved organic matter. The limit of quantification (LOQ) for F was 1.3 µg g-1 (using 2.1 g of seafood), which is almost 4 times lower than the LOQ obtained using the reference method (pyrohydrolysis). Contrary to the reference method, this relatively low LOQ allowed the determination of F in all the seafood samples analysed. Taking into account that only 6 mL of diluted NH4OH solution (50 mmol L-1) were used and the suitable LOQ, the proposed sequential digestion MIC method can be recommended for further F determination in trace levels in seafood, even using a low-cost technique such as ISE, instead of other, more powerful techniques, such as ion chromatography.

Determination of Cl, Br and I in soils by ICP-MS: microwave-assisted wet partial digestion using H2O2 in an ultra-high pressure system

In this study, we proposed a method for halogen determination using inductively coupled plasma mass spectrometry (ICP-MS) after partial digestion of soils using only H2O2 as a reagent for organic matrix decomposition. It was performed by microwave-assisted wet digestion (MAWD) using a high-pressure single reaction chamber (SRC) system and found to be feasible for the digestion of soils with intermediate or high organic matter (OM) content. The following parameters were evaluated for the MAWD-SRC method: the OM content in soils (50 and 98%), temperature of microwave heating (from 200 to 270 °C), and volume of H2O2 (5 or 10 mL). Initially, soils were digested by the MIC method to obtain the reference values. Using the optimized conditions, 50 and 25 mg of soils containing 50 and 98% of OM, respectively, were efficiently digested using only 5 mL of 50% H2O2 solution and a maximum temperature of 250 °C. For I, results were affected when digestion temperatures lower than 250 °C were used probably due to the formation of I2 during nebulization by ICP-MS. The agreement between the results was in the range from 95 to 106% for Cl, Br, and I after digestion of both types of soils. Relatively low limits of quantification (LOQs), especially for Br and I, were obtained, i.e. 132 and 264 μg g−1 for Cl, 0.06 and 0.13 μg g−1 for Br, and 0.03 and 0.05 μg g−1 for I, considering 50 and 25 mg of soil, respectively. Accuracy was evaluated by comparing the results with those obtained via combustion followed by the pyrohydrolysis method and by the analysis of a certified reference material (CRM). No statistical difference was observed between the results obtained using both methods and the values of CRM. The MAWD-SRC method that uses only H2O2 has been considered as an alternative for the effective digestion of OM in soils with an intermediate or high OM for the further determination of Cl, Br, and I by ICP-MS.

Use of chitin as a template for the preparation of mesostructured ZSM-5

In this work, mesostructured ZSM-5 zeolite was prepared using chitin as a new template to produce mesoporosity. Different amounts of chitin were used for the synthesis of ZSM-5 in order to verify its influence on the formation of mesopores. All samples were prepared by conventional hydrothermal process. For comparison purposes, ZSM-5 zeolite has also been synthesized without a presence of chitin. The samples were characterized by X-ray diffraction, scanning electron microscopy and N2 adsorption techniques. Experimental results showed that the mesopores volume of the obtained samples increased with increasing amount of chitin in the reaction mixture. Therefore, chitin showed to be a promising template for obtaining the ZSM-5 with mesoporous property.