Physicochemical Characterization of Pulp and Black Liquor Derived from Corn Husk and Coir Blends

This study investigates the suitability of an agrowaste biomass blend, specifically corn husk and coconut coir, for producing sustainable pulp through kraft pulping and elemental chlorinefree (ECF) bleaching. An equal weight ratio (1:1 w/w) of oven-dried corn husk and coir was pretreated with steam at 120°C for one hour, then subjected to kraft pulping in a batch reactor at 80°C for two hours using white liquor (NaOH and Na₂S) at a solid-to-liquid ratio of 1:18. The unbleached pulp, with a yield of 38.7%, was bleached with hydrogen peroxide (1:10 w/v pulp-to-peroxide ratio) at 60°C for one hour. The properties of both unbleached and bleached pulps were analyzed using Fourier transform infrared (FTIR) spectroscopy, water retention value (WRV), cellulose content measurement, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and thermogravimetric analysis (TGA). Black liquor from the pulping process was examined via UV–visible spectroscopy. SEM images revealed a fibril-bound network in unbleached pulp, which became more porous and fibrillated after bleaching. FTIR spectra confirmed lignin removal by decreased aromatic bands in the 1600–1400 cm⁻¹ range. The cellulose content increased from 60.2% to 85.4% post-bleaching. Elevated WRV indicated enhanced fiber swelling and porosity. TGA showed thermal degradation peaks between 200–350°C in bleached pulp, signifying improved thermal stability. UV-Vis analysis of black liquor revealed significant lignin peaks (an absorbance of 0.8 at 200–205 nm), indicating effective lignin removal. Overall, these results demonstrate that the pulping and bleaching procedures are viable for producing highquality, cellulose-based pulp suitable for environmentally friendly applications.