Ultrafine Kaolinite Removal in Recycled Water from the Overflow of Thickener Using Electroflotation: A Novel Application of Saline Water Splitting in Mineral Processing.

The presence of ultrafine clay particles that are difficult to remove by conventional filtration creates many operational problems in mining processing systems. In this work, the removal of clay suspensions has been investigated using an electroflotation (EF) process with titanium electrodes. The results show that EF is a viable and novel alternative for removing ultrafine particles of kaolinite-type clay present in sedimentation tank overflows with low salt concentrations (<0.1 mol/L) in copper mining facilities based on the saline water splitting concept. Maximum suspended solid removal values of 91.4 and 83.2% in NaCl and KCl solutions, respectively, were obtained under the experimental conditions of the constant applied potential of 20 V/SHE, salinity concentration of 0.1 mol/L, and electroflotation time of 10 and 20 min in NaCl and KCl solutions, respectively. Furthermore, the visual evidence of particle aggregation by flocculation during the experiments indicates a synergy between EF and electrocoagulation (EC) that enhances the removal of ultrafine particles of kaolinite.

Corrosion of Reinforced A630-420H Steel in Direct Contact with NaCl Solution.

The deterioration of reinforced concrete structures in marine environments presents multiple problems due to the premature degradation of reinforced steel. This work aimed to study the corrosion of reinforced A630-420H steel when exposed to a 0.5 M NaCl solution. Although this carbon steel is the most widely used material for reinforced concrete structures in Chile, there is limited research on its resistance to corrosion when in contact with saline solutions. The electrochemical reactions and their roles in the corrosion rate were studied using linear sweep voltammetry, weight loss, scanning electron microscopy, and X-ray diffraction techniques. This analysis is unique as it used the superposition model based on mixed potential theory to determine the electrochemical and corrosion parameters. The outcomes of this study show that A630-420H steel has a higher corrosion rate than those of the other commercial carbon steels studied. This fact can be attributed to the competition between the cathodic oxygen reduction reaction and hydrogen evolution reaction, which also depends on the environmental conditions, exposure time, stabilization of the corrosion products layer, and presence of chloride ions. Additionally, the results under mechanical stress conditions show a brittle fracture of the corrosion product oriented longitudinally in the direction of the bend section, where the presence of pores and cracks were also observed. The corrosion products after corrosion were mainly composed of magnetite and lepidocrocite oxide phases, which is in concordance with the electrochemical results.

Corrosion of Titanium Electrode Used for Solar Saline Electroflotation.

The solar electroflotation (EF) processes using saline electrolytes are today one of the great challenges for the development of electrochemical devices, due to the corrosion problems that are generated during the operation by being in permanent contact with Cl- ions. This manuscript discloses the corrosion behavior of titanium electrodes using a superposition model based on mixed potential theory and the evaluation of the superficial performance of the Ti electrodes operated to 4 V/SHE solar electroflotation in contact with a solution of 0.5 M NaCl. Additionally provided is an electrochemical analysis of Ti electrodes regarding HER, ORR, OER, and CER that occur during the solar saline EF process. The non-linear superposition model by mixed potential theory gives electrochemical and corrosion parameters that complement the information published in scientific journals, the corrosion current density and corrosion potential in these conditions is 0.069 A/m2 and -7.27 mV, respectively. The formation of TiO2 and TiOCl on the anode electrode was visualized, resulting in a reduction of its weight loss of the anode electrode.

An In Situ Evaluation of Different CAM Plants as Plant Microbial Fuel Cells for Energy Recovery in the Atacama Desert.

Excess energy derived from photosynthesis can be used in plant microbial fuel cell (PMFC) systems as a sustainable alternative for the generation of electricity. In this study, the in situ performance of CAM (Crassulacean acid metabolism) plants in Calama, in the Atacama Desert, was evaluated for energy recovery using PMFCs with stainless steel AISI 316L and Cu as electrodes. The plant species evaluated included Aloe perfoliata, Cereus jamacaru, Austrocylindropuntia subulata, Agave potatorum, Aloe arborescens, Malephora crocea, and Kalanchoe daigremontiana. Among the plant species, Kalanchoe daigremontiana demonstrated significant potential as an in situ PMFC, showing a maximum cell potential of 0.248 V and a minimum of 0.139 V. In addition, the cumulative energy for recovery was about 9.4 mWh m-2 of the electrode. The use of CAM plants in PMFCs presents a novel approach for green energy generation, as these plants possess an inherent ability to adapt to arid environments and water-scarce areas such as the Atacama Desert climate.