Utilization of Incense Stick Ash in Hydrometallurgy Methods for Extracting Oxides of Fe, Al, Si, and Ca

With rapid industrialization, there is an ever-increasing demand for iron oxides, calcium oxides, aluminum oxides, silica, and zeolites as raw materials for various industries, but reserves of such metal oxides are continuously diminishing. Therefore, there is an urgent need to explore new alternatives for such value-added minerals. One such material is incense stick ash (ISA), which is among the most unexplored byproducts from residential and holy places. Currently, ISA is of no use and it is disposed of in millions of tons (MTs) in rivers and other water bodies in India due to its sacred value. The major chemical composition of ISA is calcium, silica, alumina, ferrous minerals, magnesium, and traces of Na, K, P, Ti, etc. Major fractions of ISA, i.e., 50–60%, are made up of calcium and magnesium oxides; 20–30% of ISA is made up of silica, alumina, and ferrous minerals, as revealed by X-ray fluorescence spectroscopy (XRF). In the present research work, methods of recovery of value-added micro and nano minerals from ISA are suggested, using cost-effective techniques and an eco-friendly approach. Firstly, magnetic fractions were recovered by a magnetic separation method; then, alumina, silica, and calcium oxides were synthesized from non-magnetic fractions. The confirmation of the synthesized and extracted nanomaterials was done by Fourier transform infrared spectroscopy (FTIR), particle size analyzer (PSA), X-ray diffraction (XRD), field emission scanning electron microscopy with electron diffraction spectroscopy (FESEM-EDS), and transmission electron microscopy (TEM). The purity of synthesized particles varied from 40–80%. In the future, ISA will prove to be an alternative resource material for Fe, Ca, Si, C, Al, and zeolites, which will minimize solid waste pollution and water pollution arising due to the disposal of ISA into water bodies.