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

Abstract

The current research work examines the suitability of agrowaste biomass blend i.e corn husk and coconut coir for production of sustainable pulp using kraft pulping and Elemental Chlorine-Free (ECF) bleaching. An equal amount of oven-dried corn husk and coir (1:1 w/w) was pre-treated by steam at 120^oC 1 hour and then kraft pulped in a batch reactor at 80^oC for 2 hours with white liquor (NaOH and Na₂S) in a 1:18 solid-to-liquid ratio. The unbleached pulp with a yield of 38.7 was bleached with hydrogen peroxide (1:10 w/v pulp-to-peroxide ratio) at 60^oC over 1 hour. The properties of unbleached and bleached pulps were determined for several properties using FTIR data, Water retention value, Cellulose content, SEM, EDX and TGA. The analysis of black liquor collected in the reactor, following pulping, was carried out with the help of UV-Visible spectrophotometer. Analysis of SEM showed a fibril-bound network in unbleached pulp to a more porous and fibrillated structure more in bleached fibers. The elimination of lignin was established through FTIR spectra by reduction of aromatic bands in the range of 1600 1400 cm⁻¹ range. The total cellulose percent improved from 60.2 to 85.4 after bleaching. The Water retention value was also better, which showed increased swelling and porosity of the fiber. TGA showed thermal degradation peaks between 200–350°C in bleached pulp, indicating improved thermal stability. The UV-visible analysis of black liquor has shown considerable lignin peaks (Absorption-0.8 at wavelength 200-205 nm) which suggests considerable removal of lignin from wood cells. The findings of this study confirm the viability of the employed pulping and bleaching regimes in the manufacture of fine quality, cellulose-based pulp to be utilized in the manufacture of environmentally-friendly material applications.