Acid leaching of LiCoO2 enhanced by reducing agent. Model formulation and validation

In this work, a model has been formulated to describe the complex process of LiCoO₂ leaching through the participation of competing reactions in acid media including the effect of H₂O₂ as reducing agent. The model presented here describes the extraction of Li and Co in the presence and absence of H₂O₂, and it takes into account the different phenomena affecting the controlling mechanisms. In this context, the model predicts the swift from kinetic control to diffusion control. The model has been implemented and solved to simulate the leaching process. To validate the model and to estimate the model parameters, a set of 12 (in triplicate) extraction experiments were carried out varying the concentration of hydrochloric acid (within the range of 0.5-2.5 M) and hydrogen peroxide (range 0-0.6%v/v). The simulation results match fairly well with the experimental data for a wide range of conditions. Furthermore, the model can be used to predict results with different solid-liquid ratios as well as different acid and oxygen peroxide concentrations. This model could be used to design or optimize a LiCoO₂ extraction process facilitating the corresponding economical balance of the treatment.

Sustainability of construction materials: Electrodialytic technology as a tool for mortars production

The reduction of tap water consumption in all activity sectors, including the building industry, is crucial to the sustainability of water resources. Effluents from wastewater treatment plants have the potential to replace freshwater in the construction sector but they contain a critical mixture of impurities, which hampers their use in mortars production. In this work, the viability of using effluent as an alternative to potable water for the production of mortars, after electrodialytic treatment, was assessed. Electrodialytic technology (ED-T) is a proven technique for decontamination of porous and aqueous matrices. ED-T experiments were conducted with 500 mL of effluent for 6, 12 and 24 h, with a current intensity of 25 mA. The results showed that after ED-T 6 h, the removal efficiencies of critical components were above 85% of their initial concentrations. Mortar properties such as setting time, workability, flexural strength, compressive strength and morphology were obtained for 100% effluent and tap water/effluent mixtures (50:50) with and without ED-T pre-treatment. The mortars with the ED-T treated effluent showed similar initial setting times and workability, higher flexural and compressive strength compared to the mortars reference.

Investigating the evolving microstructure of lithium metal electrodes in 3D using X-ray computed tomography

The growth of dendritic and mossy deposits through the separator of lithium batteries can result in battery short circuiting and failure. In situ X-ray CT provides insight into evolution of lithium-metal electrodes during battery operation.

Energy from CO2 using capacitive electrodes - a model for energy extraction cycles

A model is presented for the process of harvesting electrical energy from CO2 emissions using capacitive cells. The principle consists of controlling the mixing process of a concentrated CO2 gas stream with a dilute CO2 gas stream (as, for example, exhaust gas and air), thereby converting part of the released mixing energy into electrical energy. The model describes the transient reactive transport of CO2 gas absorbed in water or in monoethanolamine (MEA) solutions, under the assumption of local chemical equilibrium. The model combines the selective transport of ions through ion-exchange membranes, the accumulation of charge in the porous carbon electrodes and the coupling between the ionic current and the produced electrical current and power. We demonstrate that the model can be used to calculate the energy that can be extracted by mixing concentrated and dilute CO2 containing gas streams. Our calculation results for the process using MEA solutions have various counterintuitive features, including: 1. When dynamic equilibrium is reached in the cyclical process, the electrical charge in the anode is negative both during charging and discharging; 2. Placing an anion-exchange membrane (AEM) in the system is not required, the energy per cycle is just as large with or without an AEM.