Evaluation of basic waste from the lithium industry as a main component of constructive materials

In recent years, the lithium industry has had strong growth worldwide. One of the lithium resources is the enriched brines in salar flats. To our knowledge, in Argentina, residues of lithium extraction industries are disposed of in the salar flat due to their non-hazardous characteristics (they are mostly salts such as NaCl, KCl, and basic residues from lime precipitation). Due to the large amount of solid waste generated, it is necessary to find mitigation strategies. The objective of this work is to investigate the use of these residues as constructive material. It would be a contribution to mitigate the environmental impact of waste disposal, and fostering recycling and circular economy. This waste, which is mainly magnesium hydroxide and gypsum, was combined with different additives such as cement, paper pulp, froth additives and prickly pear water. Prototypes were physicochemically (chemical composition, density, morphology, and thermal conductivity), and mechanically characterized (compressive strength). This research presents preliminary results. Washed raw material combined with prickly pear water has the lowest density (2.31 g/cm 3 ) and the most airy structure, while it has a thermal conductivity of 0.13-0.16 W/m K, values comparable with those of other combined constructive materials, such as gypsum boards integrated with microencapsulated phase change materials. Additionally, the specimens made from mixtures with ratios of 2 and 2.4 exhibited the highest compressive strength values (1.69-2.02 MPa). Prototypes composed of washed raw material (WRM) combined with cement, achieved values of compressive strength of 6.17 MPa after seven days and maintaining values above 3.78 MPa after 28 days. For all prototypes, their compressive strength values are comparable to those of eco-bricks. These results, though preliminary, are promising. It is a first step to reusing or recycling waste from the lithium industry, contributing to environmental remediation and circular economy. • During the process to obtain lithium carbonate from brines, large amounts of non-hazardous solid waste are generated and disposed, in the same salar flat, in the form of piles since they are not useful for the industry. • The proposed environmental strategy could reduce the amount of solid waste accumulated in the salar flats and minimize the use of other materials with a high CO 2 footprint such as cement. • The prototypes could be used for different types of masonry, ccontributing to mitigate the environmental impact of brine treatment.