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The use of mineral clays as alternative adsorbent has received attention due to their physicochemical characteristics, superficial negative charge, abundance of vermiculite (especially in Brazil), low cost, and chemical composition, which allows the material modification to increase the adsorptive capacity. This manuscript evaluated the use of expanded vermiculite (EV) and sodium-modified vermiculite (VNa) in the adsorption and ion exchange of Cd2+ ions. The sodification was successfully carried out making the ion exchange capacity greater in the modified clay, confirmed by EDX, cation exchange capacity (CEC), DRX, and FTIR analysis. The CEC was 210 and 233 mEq/100 g for the EV and VNa, respectively, with 97.8% exchangeable ion (Na+) in the VNa. FTIR spectra showed small variations in the groups related to ion exchange and XRD analysis indicated changes in the distance of the layers with loss of crystallinity after clay modification, which was recovered after cadmium adsorption. The kinetics became faster with an equilibrium time of 10 min for VNa and 45 min for EV. Cd2+ removal by vermiculite above 99% was achieved. Pseudo-second order model best described the kinetics, in which the resistance to mass transfer in external film is the limiting step of the process and, once this resistance is overcome, the ion exchange happens quickly. Despite the decrease in surface area after sodification, the adsorptive capacity increased 158% in the sodified adsorbent, from 0.107 mmol/g for EV to 0.276 mmol/g for VNa, under the evaluated conditions. [ABSTRACT FROM AUTHOR]

In this study, four Brazilian clays (Bofe, Verde-lodo, commercial Fluidgel, and expanded commercial vermiculite) were evaluated for their adsorptive capacity and removal percentage in relation to different toxic metals (Ni 2+ , Cd 2+ , Zn 2+ , and Cu 2+ ). The best results were obtained by expanded vermiculite, with cadmium removal reaching values of 95%. The most promising clay was modified by the sodification process, and the metal cadmium was used to evaluate the ion exchange process. The clays expanded vermiculite (EV) and VNa-sodified vermiculite were evaluated by equilibrium study at 25, 35, and 45 °C. At 25 °C, EV obtained a maximum adsorption capacity of 0.368 mmol/g and sodified vermiculite 0.480 mmol/g, which represents an improvement of 30.4% in modified clay capacity. At 45 °C, the sodified vermiculite reached 0.970 mmol/g adsorption capacity. The Langmuir, Redlich-Peterson Freundlich, and Dubinin-Raduskevich models were adjusted to the results. Langmuir provided the best fit among the models. The thermodynamic quantities (ΔS, ΔH, and ΔG) demonstrated that the process is spontaneous and endothermic and the metal is captured by physisorption and chemisorption in the studied temperature range. For the ion exchange equilibrium, the binary Langmuir and binary Langmuir-Freundlich models were adjusted to the expanded vermiculite and sodified vermiculite isotherms, respectively. Both models were predictive. Thermal analysis indicated good heat resistance even after material modification. The apparent and real densities demonstrated that after each treatment or contamination, the clayey material undergoes contraction in its structure. An improved efficiency of the adsorbent was found after sodification., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Low salinity water injection (LSWI) has been studied by several researchers as an enhanced oil recovery (EOR) method in laboratory experiments, numerical simulations, and field applications. However, its effects on oil recovery remain uncertain due to the complexity of the interactions among crude oil, brine, and the rock surface, for both sandstone and carbonate reservoirs, particularly when they contain a diversity of clay minerals. This paper investigates LSWI performance and mechanisms in sandstone rock, brine, and light crude oil with low polar compounds from a reservoir in Brazil. Core flooding experiments and reservoir simulations were carried out to understand the influence of key parameters on oil recovery. Zeta potential measurements were performed to investigate the influence of the formation water and NaCl and CaCl 2 brine solutions on rock and oil surface charges. Increased oil recovery, Ca++ desorption from the rock surface, and a substantial pH increase in the effluent were noticed during LSWI. Based on the zeta potential measurement, a thicker water film was also formed on the rock and oil surface with brine dilution. A recovery factor of 64% was reached by testing LSWI from the beginning of the waterflooding (secondary mode) and this was the highest recovery of all the scenarios evaluated. Ten parameters were successfully history matched to core flood data, and optimization and sensitivity analysis showed that the concentration of Na+ and Ca++, and the water injection rate were the most important parameters in the LSWI process. Overall, this study sheds light on the LSWI mechanisms for the Brazilian oil field investigated and provides useful operational parameters for designing and achieving better LSWI performance. [Display omitted] • Core flooding performed with samples from an oil field in northeastern Brazil. • Higher oil recovery the earlier the diluted SFW cycling is applied. • Development of core flooding model with laboratory data for similar reservoirs. • Optimization and uncertainty assessment of critical operational parameters. [ABSTRACT FROM AUTHOR]

• Importance of the brine pH and the isoelectric point of mineral for wettability. • pH increase induced by low salinity brine favors oil release and fine migration. • Botucatu sandstone is sensitive to salinity reduction as Berea and Bentheimer. Low salinity water injection (LSWI) is a current and cost-effective method to enhance oil recovery by changing the salinity and composition of the injected water. However, the synergistic effect of chemical composition, concentration and in particular the pH of the brine in oil recovery during LSWI remains not well understood. In addition, there is a lack of low salinity studies in Brazilian sandstone rocks and light paraffinic crude oils of low acid/basic number to date. This paper investigates oil recovery mechanisms and the pH effect in high and low salinity brine solutions using samples from a clastic reservoir in Recôncavo basin, northeastern Brazil. Zeta potential and interfacial tension measurements, oil adsorption analysis using a quartz crystal microbalance with dissipation monitoring, and core flooding experiments were performed using different concentrations and pH values of synthetic formation water (SFW), NaCl and CaCl 2 brine solutions. The results indicate that when the reservoir pH changes towards the alkaline conditions driven by ionic exchanges during LSWI, it may approximate the isoelectric point (IEP) of pH-dependent surface charges in oil and rock minerals, weakening the electrostatic attraction between their surfaces, and consequently contributing to increased oil recovery. The findings of this study can help understand oil recovery mechanisms during LSWI according to the type and content of pH-dependent surface charges in sandstone rocks and crude oils. This study also shows how to pre-select potential field candidates in the Recôncavo basin and similar formations for stand-alone and hybrid LSWI applications. [ABSTRACT FROM AUTHOR]

The current work addresses the study of the recovery of rare earth elements (REE) from acid mine water by using cationic exchange resin. The acid water was obtained from a closed uranium mine in Brazil. Ion exchange experiments were carried out in batch with three different resins at 25 ± 0.5°C and pH values 1.4, 2.4 and 3.4 (natural). Data were adjusted to the Langmuir equation in order to calculate the maximum loading capacity (q max ) of the resins. The results of q max for individual REE revealed that the resins present higher loading for La in detriment to the other REE. The Dowex 50WX8 and Lewatit MDS 200 H resins demonstrated favourable sorption profiles to REE, evidenced by values of equilibrium factor (R L ) and higher values of the Langmuir constants (b). The separation factors ( α H R E E L R E E ) indicates that resins are more selective for light REE at all pH studied. The selectivity of the resins for the REE can be described as light REE > heavy REE. The pH 1.4 and 3.4 are more favourable for the recovery of REE.

Over the past few years, supercritical water oxidation (ScWO) has shown great potential for application to landfill leachate treatment, providing substantial organic matter degradation in terms of biochemical oxygen demand (BOD), chemical oxygen demand (COD), and total organic carbon (TOC). However, the conversion of ammonia, which is present at high concentrations in leachates, is the rate-limiting step during ScWO and usually requires large amounts of oxidants, the addition of catalysts, or severe operating conditions. Aiming at proposing a treatment system that effectively removes both organic matter and ammonia from leachate, this paper evaluates the intensification of the ScWO process through ion exchange with zeolite. Thus, ScWO was operated under a pressure of 23 MPa at 600 and 700 °C, without the addition of oxidants. The zeolite (clinoptilolite) was used without any modification inside a glass column. The ScWO (600 °C)/zeolite system removed 90% ammoniacal nitrogen (NH 3 -N), 100% nitrite (NO 2 -N), 98% nitrate (NO 3 -N), color, and turbidity, 81% TOC, and 74% COD, suggesting that this system is a promising alternative for leachate treatment. However, the final NH 3 -N and COD values were slightly above the limits (20 and 200 mg L -1 , respectively) stipulated by the Brazilian environmental legislation. These results suggest that further improvements are still required for the application of the intensified ScWO to be feasible. Notably, ammonium-saturated clinoptilolite is amenable for regeneration or can be applied to soil as a slow-release fertilizer., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

The alginate extraction residue (RES) from the Brazilian Sargassum filipendula was successfully employed as biosorbent in this binary equilibrium study, revealing a greater affinity and selectivity for Cr(III) than for Zn(II). Experimental results also revealed that the process is of endothermic nature and well adjusted by Langmuir-Freundlich binary model. The X-ray photoelectron spectroscopy (XPS) analysis revealed that coordination with hydroxyl groups of RES prevailed in Cr removal, followed by carboxyl-metal complexation. As far as Zn(II) is concerned, ion exchange with carboxylate groups of RES was the largest contributor. Nevertheless, scanning electron microscopy coupled with Fourier transform infrared spectroscopy indicated the participation of sulfate functions in a minor degree.