Structural and physicochemical properties of microcrystalline cellulose isolated from waste paper pulp using citric acid hydrolysis

Microcrystalline cellulose (MCC) was isolated from waste paper pulp using an eco-friendly approach based on citric acid hydrolysis, offering a green alternative to conventional mineral acids. This study investigated the influence of citric acid concentration (3 M, 4 M, and 5 M) on the resulting MCC's properties, followed by purification and bleaching. The optimal condition was achieved with 4 M citric acid (MCC4), which produced MCC with a high crystallinity index (80.2%), a substantial yield (78.1%), and excellent thermal stability (T peak = 350.5 °C). The isolated rod-shaped MCC from paper pulp showed the particle dimension in the average of 14.98 μm with a narrow distribution. A comprehensive physicochemical analysis demonstrated that the properties of the resulting MCC (including density, pH, and ash content) were highly comparable to commercial Avicel PH-101. Notably, the prepared MCC4 exhibited superior functional properties, specifically higher water holding capacity (2.95 g/g) and oil holding capacity (3.05 g/g). The findings demonstrate that citric acid hydrolysis is a highly effective, non-corrosive, and environmentally friendly alternative to traditional mineral acid methods for MCC production. This research provides a viable pathway for transforming paper waste into high-value bioproducts suitable for pharmaceutical, food, and composite applications, contributing to a circular bio-economy. • An eco-friendly citric acid hydrolysis method was applied to waste paper pulp. • 4 M citric acid concentration optimized the yield (78.1%) and crystallinity (80.2%). • The produced MCC exhibited excellent thermal stability (T peak = 350.5 °C). • Physicochemical properties of the resulting MCC were comparable to Avicel PH-101. • Water (WHC) and oil (OHC) holding capacities were superior to the commercial standard.