The comparison of hydrothermal, ultrasonication and microwave assisted alkalization of cellulose from Borassus flabellifer fruit husk

This study compares the effect of physical treatment to facilitate the alkalization of Borassus flabellifer fruit husk to produce microcrystalline cellulose. Alkalization using NaOH solution was combined with hydrothermal, ultrasonication, and microwave irradiation to achieve efficient lignin removal. Choosing the proper alkalization treatment is essential to enhance cellulose content and thermal stability while reducing surface corrugation of microcrystalline cellulose. High lignin separation was obtained using microwave-assisted alkalization followed by ultrasonication, conventional heating, and hydrothermal methods. Microwave irradiation offers rapid lignin removal from 11.8% to only 0.16 %, producing 74% cellulose content with the highest cellulose yield of 29.82%. Microcrystalline fibers with smooth morphology were produced at an estimated 51.42 μm diameter. The transition from cellulose I to cellulose II was evidenced by the shift of the FTIR band from 2924 cm⁻¹ to 2895 cm⁻¹ and the three characteristic peaks for cellulose II at 2θ = 12, 20.1 and 21.7° in XRD.