Evaporitic technology for lithium mining from brines has been questioned for its intensive water use, protracted duration and exclusive application to continental brines. In this Review, we analyse the environmental impacts of evaporitic and alternative technologies, collectively known as direct lithium extraction (DLE), for lithium mining, focusing on requirements for fresh water, chemicals, energy consumption and waste generation, including spent brines. DLE technologies aim to tackle the environmental and techno-economic shortcomings of current practice by avoiding brine evaporation. A selection of DLE technologies has achieved Li + recovery above 95%, Li + /Mg 2+ separation above 100, and zero chemical approaches. Conversely, only 30% of DLE test experiments were performed on real brines, and thus the effect of multivalent ions or large Na + /Li + concentration differences on performance indicators is often not evaluated. Some DLE technologies involve brine pH changes or brine heating up to 80 o C for improved Li + recovery, which require energy, fresh water and chemicals that must be considered during environmental impact assessments. Future research should focus on performing tests on real brines and achieving competitiveness in several performance indicators simultaneously. The environmental impact of DLE should be assessed from brine pumping to the production of the pure solid lithium product. Sections Lithium mining from continental brinesAs of 2022, worldwide, there are eight full-scale active facilities that produce lithium compounds from continental brines 9 and more are likely to become active before 2030 (Fig. 1a). The evaporitic technology (Fig. 1b) is currently in use at seven of those facilities 18,19 . Brines are Key points• Fresh water consumption of direct lithium extraction (DLE) needs to be urgently quantified. Many DLE technologies might require larger freshwater volumes than current evaporative practices, compromising their applicability in arid locations.• Environmental monitoring guidelines have been drafted with evaporitic technology in mind, but they should also be applied to the implementation of any DLE technology, which still consumes brine, uses fresh water and produces residues, the latter two hopefully at considerably lower volumes.Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author selfarchiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.

No abstract

No abstract

The influence of sol-gel dip-coating and anodic oxidation process parameters in producing thin TiO2 films is studied. As the size of the films is in the order of nanometres (20-140 nm), to obtain a precise measurement of their thickness and analyse their crystalline structures, glancing incidence angle X-ray techniques (X-ray reflectometry and Xray diffraction) using synchrotron radiation are used. A relationship between the colour and thickness of the films was found. This enables the film thickness to be estimated by the film colour. Within the range of the parameters studied, both techniques produce thin films with smooth surfaces which at most reproduce the roughness of the polished substrate. Independently of the technique, thermally-treated films thicker than 30 nm presented different crystalline structures with anatase and rutile phases.

No abstract

Multiscale Phenomena in SurfacesHemocompatible fi lms can be obtained by different techniques which must produce a smooth surface and a desired combination of crystal structure including rutile and anatase structures. Two of the simplest techniques include sol-gel and anodic oxidation. The characteristics of the fi lms associated with the process variables are presented. The most important characteristics of the fi lms are thickness, structure, roughness, and mechanical properties such as adhesion and wear resistance.

The bio- and hemocompatibility of titanium alloys are due to the formation of a TiO2 layer. This natural oxide may have fissures which are detrimental to its properties. Anodic oxidation is used to obtain thicker films. By means of this technique, at low voltages oxidation, amorphous and low roughness coatings are obtained, while, above a certain voltage, crystalline and porous coatings are obtained. According to the literature, the crystalline phases of TiO2, anatase, and rutile would present greater biocompatibility than the amorphous phase. On the other hand, for hemocompatible applications, smooth and homogeneous surfaces are required. One way to obtain crystalline and homogeneous coatings is by heat treatments after anodic oxidation. The aim of this study is to evaluate the influence of heat treatments on the thickness, morphology, and crystalline structure of the TiO2 anodic coatings. The characterization was performed by optical and scanning electron microscopy, X-ray diffraction, and X-ray reflectometry. Coatings with different colors of interference were obtained. There were no significant changes in the surface morphology and roughness after heat treatment of 500°C. Heat treated coatings have different proportions of the crystalline phases, depending on the voltage of anodic oxidation and the temperature of the heat treatment.

Abstract:To obtain smooth TiO 2 coatings for building a new design of Ti-6Al-4V heart valve, the anodic oxidation technique in pre-spark conditions was evaluated. TiO 2 coating is necessary for its recognized biocompatibility and corrosion resistance. A required feature on surfaces in contact with blood is a low level of roughness (R a ≤ 50 nm) that does not favor the formation of blood clots. The present paper compares the coatings obtained by anodic oxidation of the Ti-6Al-4V alloy using H 2 SO 4 at different concentrations (0.1-4 M) as electrolyte and applying different voltages (from 20 to 70 V). Color and morphological analysis of coatings are performed using optical and scanning microscopy. The crystalline phases were analyzed by glancing X-ray diffraction. By varying the applied voltage, different interference colors coatings were obtained. The differences in morphologies of the coatings caused by changes in acid concentration are more evident at high voltages, limiting the oxidation conditions for the desired application. Anatase phase was detected from 70 V for 1 M H 2 SO 4 . An increase in the concentration of H 2 SO 4 decreases the voltage at which the transformation of amorphous to crystalline coatings occurs; i.e., with 4 M H 2 SO 4 , the anatase phase appears at 60 V.