Study and Development of Shola-based Sustainable Materials for Environmental and Industrial Applications

Mondal, Keya (2025) Study and Development of Shola-based Sustainable Materials for Environmental and Industrial Applications. PhD thesis, Indian Institute of Science Education and Research Kolkata.

Text (PhD thesis of Keya Mondal (19RS108)) 19RS108.pdf - Submitted Version Restricted to Repository staff only Download (13MB)

Abstract

Transitioning from the linear economic era to a sustainable circular future requires not only the adoption of renewable materials but also their integration into circular systems that promote resource efficiency, reuse, recycling, and regeneration. Natural polymers derived from lignocellulosic materials are often considered more environmentally friendly than their petroleum-based synthetic analogues. One such promising lignocellulosic material is Shola, a dried, milky-white shrub of the Aeschynomene genus, native to the wetlands of eastern India. The white inner stem, Shola pith, is a light, soft, spongy material traditionally used by Bengal artisans for decorative items in social and religious ceremonies. Visually, it appears similar to Thermocol but is superior in malleability, texture, lustre, and sponginess. The unique and intriguing colour, texture, and feel of the Shola pith led us to explore in depth the physical structure and chemical properties of this abundantly available biomass and explore potential applications that uniquely exploit its physicochemical properties. The Shola pith has an exquisite three-dimensional and hierarchical porous architecture created by nature. The pith consists of about 70 wt.% cellulose as the main chemical component, which is much higher than what is found in other lignocellulosic sources. The Shola pith surface shows a high-water contact angle (135°) and rapid oil spreading, demonstrating strong hydrophobic–oleophilic behaviour. It exhibits a high oil sorption capacity (40–60 g/g) and selectively sorbs oil from both oil–water biphasic mixtures and emulsions, leaving the water surface clean. Thus, Shola pith serves as an efficient 3D porous natural sorbent for oil/water separation. Beyond its sorption capability, Shola pith has also been transformed into regenerated cellulose particles via a simple one-step acid hydrolysis using ortho-phosphoric acid. Submicron spherical cellulose particles show strong water dispersibility and can efficiently stabilise oil–water interfaces, forming stable Pickering emulsions. They also promote the emulsion polymerisation of monomers such as methyl methacrylate and styrene, yielding uniform and stable polymer particles. These properties demonstrate the potential of regenerated cellulose as a sustainable substitute for synthetic surfactants in industrial processes. In addition, Shola pith shows strong potential as a feedstock for second-generation bioethanol due to its high cellulose, low lignin, and low crystallinity, which improve enzymatic digestibility. Optimised pretreatment and saccharification produced 69 wt.% glucose, readily fermentable to ethanol. Furthermore, Shola pith enabled the direct one-step synthesis of carboxy nanocellulose via TEMPO-mediated oxidation, eliminating the need for any prior pretreatment. In conclusion, our investigation reveals that Shola holds immense potential as a sustainable material across diverse scientific and industrial applications, marking a holistic transition from heritage to high-tech innovation.

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