Comparison of solids in effluent from pulping kenaf stem with formic acid and sodium hydroxide

Abstract

The pulp and paper industry is the sixth largest polluter discharging a variety of gaseous, liquid and solid wastes into the environment. This pollution mainly arises due to chemicals used during production, so this study compared these two chemicals to determine the better one for a cleaner production process. A dewatered kenaf stem was cooked in the 20, 60 and 90% concentrations of formic acid and sodium hydroxide at time intervals of 1, 2 and 3 h to compare the solids (total suspended solid, total dissolved solid and total solid) of their effluent for environmental friendliness. After examining the whole concentrations and the time intervals, 60% concentration of the acids at 2 h pulping gave better pulp on physical examination. When the solids of the effluents of the two chemicals were analyzed, formic acid effluent had a TSS of 5768 mg/L, TDS of 54088 mg/L and TS of 59855 mg/L, while that of sodium hydroxide was 6053 mg/L for TSS, 96628 mg/L for TDS and 102680 mg/L for TS. This study showed that pulping of kenaf stem with 60% formic acid for 2 h has effluent that is greener than the use of sodium hydroxide of the same concentration at the same duration.

Characteristics of Effluent from Formic Acid and Sodium Hydroxide Pulping of Kenaf Stem

“…The chemical pulping method involves the addition of chemicals that eventually separates the fibres through degradation of the lignin and hemicelluloses into small water-soluble molecules. The most commonly used chemical methods are the Kraft pulping, sulphite pulping, soda pulping, and organosolv pulping processes [16]. The soda pulping process involves the cooking of the biomass with either sodium carbonate or both sodium carbonate and sodium hydroxide [17].…”

“…Total dissolved solids (TDS) are measured as the mass of residue remaining when a measured volume of filtered water is evaporated. Total solids (TS) are the amount of solid present in dissolved and suspended form [22]. In the recent past due to the advancement of analytical facilities, some researchers have detected a complex mixture of organic and inorganic compounds as residual recalcitrant pollutants present in pulp paper mill effluent after secondary treatment [23,24].…”