Eco-efficient pickering foams: leveraging sugarcane waste-derived cellulose nanofibres

Abstract

Foams, known for their diverse material properties, are extensively utilised in fields ranging from food and cosmetics to environmental remediation and mineral processing. Stable foam formation typically requires surface-active substances, such as surfactants, to lower the surface free energy at the air–liquid interface. However, many current foam stabilisers pose environmental risks due to toxicity and non-biodegradability. This study presents cellulose nanofibers (CNF) derived from agricultural waste, as an eco-friendly foam stabiliser. The less dense structure of non-wood biomass yields high aspect ratio and flexible nanofibers, positioning agricultural waste-derived nanofibers as a potential foam stabilising agent. To achieve varying foam stabilities for different applications, the foam generation and stability of 0.1 wt% CNF with different amounts of octylamine (OA) are examined. Insights into the stabilising effect of CNF and OA are drawn from the interfacial tension and dilational rheology of OA and CNF adsorbed layers. Results showed that foam stability peaked with OA concentration at 630 ppm; beyond this, stability decreased because of nanofiber aggregation. The enhanced foam stability is attributed to the increased surface hydrophobicity with OA concentration, which promotes nanofiber adsorption at the air–water interface and improves the interfacial tension and dilational viscoelasticity. Overall, this study provides valuable insights into using agricultural waste-derived nanocellulose as an efficient, eco-friendly, and economical stabilising agent for wet foams.