Rheological assessment of the interaction between hydrophobic nanoclay and xanthan gum in saline environment, for application in drilling nanofluid

In the last decade, exploration in high temperature and pressure wells has motivated the improvement of drilling fluids with the application of nanoparticles. In this context, nanoclay, the most available of nanoparticles, has been applied in the development of nanofluids, mainly associated with polymers. In parallel, among the polymers used, xanthan gum has been little explored for this purpose. In this work, the interaction between xanthan gum, hydrophobic nanoclay, sodium and calcium chloride and their influence on the rheological parameters of the mixture was evaluated in solution. The influence of temperature and hydration time on the rheological parameters of the mixture was also evaluated. For this purpose, nanoclay was first characterized with XRF, XRD and TGA. Then, a complete factorial design 24 was adopted, varying the concentrations of nanoclay, xanthan, sodium and calcium chlorides. Third, a Doehlert Matrix of the 7x5x3 type was adopted, varying the concentrations of nanoclay, xanthan and temperature, with the concentrations of the constant salts. In the fourth, select the effect of the hydration time on the color rheological parameters. Finally, Conductivity and Potential Zetas of sizes were verified, varying the concentration of the components and the hydration time of the mixtures. It was concluded that the interactions between the components of the mixture do not stabilize; the temperature, the salts have no significant influence on the rheology of the mixture; nanoclay in concentrations not exceeding 5% (m/v) interacts with the Minimum Shear Stress; the rheological parameters stabilize after 96h of hydration.

Simulation and Optimization of the CWPO Process by Combination of Aspen Plus and 6-Factor Doehlert Matrix: Towards Autothermal Operation

This work aims to present an industrial perspective on Catalytic Wet Peroxide Oxidation (CWPO) technology. Herein, process simulation and experimental design have been coupled to study the optimal process conditions to ensure high-performance oxidation, minimum H2O2 consumption and maximum energetic efficiency in an industrial scale CWPO unit. The CWPO of phenol in the presence of carbon black catalysts was studied as a model process in the Aspen Plus® v11 simulator. The kinetic model implemented, based on 30 kinetic equations with 11 organic compounds and H2O2 involvement, was valid to describe the complex reaction network and to reproduce the experimental results. The computer experiments were designed on a six-factor Doehlert Matrix in order to describe the influence of the operating conditions (i.e., the different process temperatures, inlet chemical oxygen demands, doses of H2O2 and space time) on each selected output response (conversion, efficiency of H2O2 consumption and energetic efficiency) by a quadratic model. The optimization of the WPO performance by a multi-criteria function highlighted the inlet chemical oxygen demand as the most influential operating condition. It needed to have values between 9.5 and 24 g L−1 for autothermal operation to be sustained under mild operating conditions (reaction temperature: 93–130 °C and pressure: 1–4 atm) and with a stoichiometric dose of H2O2.

A SIMPLE GREEN REDUCTION STRATEGY TO SUBSTITUTE CADMIUM IN ANALYTICAL REDUCTION OF NITRATE IN GRIESS–ILOSVAY METHOD

Nitrate is an abundant ion that is present in many industrialized products and the environment. Various analytical methods have been described using the Griess-Ilosvay reagent for the determination of nitrate in different matrices after its reduction to nitrite, in most cases with metallic cadmium as the reducer. This work proposes a new method using aluminum spheres coated with a copper film for this reduction. To optimize the method, it was important to evaluate the conditions for the deposition of the copper film on the aluminum spheres, using a Doehlert matrix. The optimized method provided an analytical range from 2.0 to 100 μmol L-1, with a coefficient of determination of 0.9996 and a standard deviation of residuals (sres) of 7.59 x 10-4. The Limits of Detection and Quantification were 0.59 and 2.0 µmol L-1 respectively. The method was applied using mineral water samples and was shown to provide repeatability less than 6.98% and accuracy obtained through recovery essays between 81.1 and 104.6% for the determination of nitrate in this type of sample.