Arundo donax L. reed: new perspectives for pulping and bleaching, part 3: ethanol reinforced alkaline pulping.APPLICATION: This study investigated the influence of process variables on yield and properties of the ethanol-alkali pulps from Arundo donax to identify optimal cooking conditions. A recent comparative analysis on the applicability of different organosolv processes to giant reed (Arundo donax L.) showed the advantages of ethanol reinforced alkaline pulping (ethanol-enhanced or ethanol-alkali pulping). Screened yield, brightness, and papermaking pa·per·mak·ing n. The process or craft of making paper. pa  per·mak properties of the ethanol-alkali pulps were superior to those for kraft and other tested organosolv pulps, while the content of residual lignin lignin (lĭg`nĭn), a highly polymerized and complex chemical compound especially common in woody plants. The cellulose walls of the wood become impregnated with lignin, a process called lignification, which greatly increases the strength and was lower. This report investigates the influence of cooking variables on yield and properties of the ethanol-alkali pulps from A. donax. The reaction medium alkalinity al·ka·lin·i·ty n. The alkali concentration or alkaline quality of a substance that contains alkali. alkalinity 1. the quality of being alkaline. 2. was a controlling factor of delignification, strongly affecting pulping selectivity. Increasing alkali charge from 5% to 35% (as NaOH on o.d. reed), at a fixed ethanol content of 40% by volume, led to a drop in residual lignin content from 20% to 3%. It also caused substantial degradation of carbohydrates and loss in pulp yield from 72% to 47%. Adding ethanol to the alkaline solution had a positive effect on carbohydrates preservation. The retention of 3.6% (on o.d. reed) non-cellulosic polysaccharides in pulps resulted from increasing ethanol content in the pulping liquor from 20% to 60% (by volume), at a fixed alkali (Old Chem.) a non-volatile base, as soda, or potash, in distinction from the volatile alkali ammonia. See also: Fixed charge of 25%. Pulp yield increased from 44% to 49% with this range of ethanol concentrations, while the content of residual lignin decreased from 5% to 3%. Changing the liquor-to-reed ratio from 5/1 to 8/1 mL/g did not reveal any appreciable influence on pulping results. Only uronic acid u·ron·ic acid n. A product of the oxidation of sugar occurring in various polysaccharides and in urine and containing both an aldehyde and a carboxyl group. moieties showed some tendency to degradation with reduced ratios on pulping. Kinetic analysis revealed three stages in the ethanol-alkali delignification. The major portion of lignin (about 71%) was removed in the rapid initial stage, actually taking place during the impregnation impregnation /im·preg·na·tion/ (im?preg-na´shun) 1. fertilization. 2. saturation (1). impregnation 1. the act of fertilizing or rendering pregnant. 2. saturation. and heating-up periods. The second (bulk) stage was comparatively short and removed only 15% of lignin. Progressive delignification with minimal carbohydrate losses resulted when the pulping duration was extended from 60 to 180 min under 140[degrees]C. View this paper online at http://www.tappi.org/index.asp?pid=28652 Anatoly A. Shatalov and Helena Pereira are with Centro de Estudos Florestais, Universidade Tecnica de Lisboa, Instituto Superior de Agronomia Instituto Superior de Agronomia (ISA), School of Agronomy - Technical University of Lisbon, is a national and international renowned faculty of excellence for graduation and post-graduation studies in Agronomy, Forestry, Food Science, Landscape Architecture, Environment, Animal , Tapada da Ajuda, 1349-017 Lisboa Codex codex Manuscript book, especially of Scripture, early literature, or ancient mythological or historical annals. The earliest type of manuscript in the form of a modern book (i.e. , Portugal. Email Shatalov at anatoly@isa.utl.pt. |
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