CORRECTED PROOF Materials Today: Proceedings xxx (xxxx) 1–6 Contents lists available at ScienceDirect Materials Today: Proceedings journal homepage: www.elsevier.com Process for recovery and value addition of silica mineral values of distinctly siliceous mining rejects Mohamed Najar ⁎ , Amrita Karn, Shweta Dhamande, Upendra Singh, Anupam Agnihotri Jawaharlal Nehru Aluminium Research Development and Design Centre, Amrawati Road, Wadi, Nagpur 440023, Maharashtra, India ARTICLE INFO Keywords: Mining rejects Khondalites Silica Beneficiation, Nano-silica Characterization ABSTRACT The mining and metal industries generate a variety of solid wastes from mining activities to finished products. Mining rejects of non-ferrous industries such as bauxite, manganese, gold, zinc, lead and copper mines are under- utilized and low in demand as potential raw materials for metallurgical use. Largely these materials are in bulk use for landfilling and building materials without recovering relevant mineral values. Major reject materials such as jarosite, kaolinite, khondalite, alumogoethite and saprolite are rich sources of alumina and silica-bearing min- eral phases with varying compositions of iron oxide as major constituents. In the present study, the chemical and mineralogy of some of these materials were assessed. The technical scope for recovering one of the low-cost min- eral phases in the rejects such as silica was ascertained for the potential value addition in view of the large scope of utilization in glass, glass products, molten sand, cement, fibreglass, ceramic enamel, sandblasting, refractory and light concrete. The recovered silica was used as a low-cost precursor for making value-added nano-silicate suitable for various industrial applications. The paper discussed the significance of the chemical composition and mineralogy of the raw materials. The process steps involved in the selective beneficiation of silicate mineral phases are used for the stepwise removal of iron oxide and alumina followed by the preparation of sodium sili- cate. Chemical precipitation and separation of nano-silica followed by characterization of silica nano-particles by scanning electron microscopy (SEM) and inductively coupled plasma (ICP)-MS analysis was also elaborated. These SEM studies inferred that the silica particles size ranges from nanometer to micrometre depending on vari- ous factors such as acid concentration, ageing time and the nature of the precursor used. ICP-MS analysis re- vealed the purity of nano-silicate prepared from the reject material. The leached solution consisting of alu- minium has been utilized for making alpha alumina based on the IPR-protected in-house process route to follow the concept of producing zero waste. © 20XX 1. Introduction The overall requirement of aluminium metal is met by two main sources of raw material from which aluminium metal is produced; bauxite ore and scrap aluminium metal, Bauxite ore is refined into alu- minium oxide by the Bayer process in an alumina plant and is further refined at an aluminium smelter to primary metal. The other source of raw material, called scrap metal, comes in two general varieties, old and new scrap which undergoes remelting or refining to metal. Both primary and secondary production of aluminium is left with a variety of solid rejects which are useful materials for production applications. These material rejects appear in the form of unprocessed solid materials of various kinds having differential chemical and mineralogical compo- sitions containing aluminium, iron and silica as major components such as mining rejects. Low-grade Bauxite (LB), Overburden Laterite (OBL) Kaolinitic Khondalite (KK), Partially Lateritic Khondalite (PLK), Lithomargic clay known as Saprolite (SL) etc. are some of the major un- processed resources suitable for commercial exploitation. Processed re- jects of aluminium production mainly represent Bauxite Residue (BR), Aluminium Dross (AD) and Spent Pot-lining Materials (SPL). Secondary aluminium (recycled aluminium) also forms a significant part of total aluminium consumption and its production requires nearly 10 to 15 times less energy than primary aluminium production [1,2]. In the recent past, the concept of reuse and recycling of industrial solid rejects has received greater attention in view of the awareness of the circular economy which emphasizes saving energy and extended life management of available resources. This leads to extensive R&D work towards maximizing the use of existing technologies for the sus- tainable and environmentally affable treatment of industrial rejects which are rich in minerals and demands low-energy process options. Awareness of environmental pollution and concern for ecological bal- ance has also created alternative ways for converting waste into wealth [3–5]. India’s growing manufacturing ambition is going to bring global issues of excessive waste with it.Hence, considering discarded materials Abbreviations: LB, Low-grade Bauxite; OBL, Overburden Laterite; KK, Kaolinitic Khondalite; PLK, Partially Lateritic Khondalite; SL, Lithomargic clay known as Saprolite; BR, Bauxite Residue; AD, Aluminium Dross; SPL, Spent Pot-lining Materials ⁎ Corresponding author. E-mail address: najar@jnarddc.gov.in (M. Najar). https://doi.org/10.1016/j.matpr.2023.05.228 2214-7853/© 20XX Note: Low-resolution images were used to create this PDF. 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