Chemical induces microstructural transformation of pulp fibre to colloidal cellulose for sustainable plant protection†

Abstract

Cellulose, an environmentally friendly material, is abundantly available in Thailand as pulp and has significant potential for use in sustainable plant protection; however, the raw material is not directly suitable for such applications. To address this, colloidal cellulose with high water dispersibility was synthesised by treating Eucalyptus pulp with sulphuric acid (H₂SO₄). The optimised conditions involved a 24 hour treatment, producing colloidal cellulose with an average particle size of 0.57 ± 0.03 μm, the smallest size achieved. The cellulose morphology, consisting of submicron and nanoscale fragments and particles, was confirmed by transmission electron microscopy, field-emission scanning electron microscopy, and dynamic light scattering analyses. This microstructural transformation, driven by H₂SO₄-induced gelatinization and regeneration, led to decreased crystallinity, as observed in X-ray diffraction patterns and infrared spectra. The formation of colloidal cellulose as a film with adhesive properties on complex plant surfaces is facilitated by hydrogen bonding and hornification mechanisms. Additionally, colloidal cellulose demonstrated high compatibility with cuprous oxide, which was used as a model agricultural protective agent, showing a reduction of over 99% in E. coli and S. aureus abundance, highlighting the potential of colloidal cellulose as a sustainable coating agent or adjuvant in agricultural protection strategies.