Advances in sustainable purification of natural clays: Methods, characterizations, challenges, applications and perspectives: A review

The expansion of modern technologies based on high-purity clays has triggered the development of sustainable and efficient enrichment processes. This review provides a critical analysis of the techniques commonly used for the purification of natural clays, with the aim of removing mineral and organic impurities. The study focuses on comparing physical, chemical, and biological methods, highlighting the strengths and weaknesses of each process as well as their environmental impacts. The results confirm the effectiveness of chemical techniques in terms of both purity and processing time, but their non-ecological nature encourages the search for more sustainable solutions. In addition, biological processes remain sustainable, but more work is needed to improve their efficiency and processing speed. On the other hand, physical methods often require a combination of other treatments to improve their performance. The enrichment levels reported in the literature do not exceed 90%, which encourages the combination of several treatment techniques to optimize yield, purity, and environmental safety. The present literature review also addresses the relationship between purification techniques and industrial requirements in more technological fields such as environmental remediation, biomedical and healthcare, advanced materials and nanocomposites, catalysis and energy technologies, agriculture, and construction/geopolymer. Swelling clays such as montmorillonite and bentonite are the most preferred in these fields due to their remarkable characteristics. The originality of this synthesis lies in the evaluation of the effectiveness, environmental friendliness, and industrialization potential of the three methods. Finally, the optimization of current methods and the integration of new long-term sustainable approaches should be the focus of future research.