Evaluation of the mild Mg(OH)2-AQ aided alkaline oxidation degumming process of ramie fiber at an industrial scale

Abstract The traditional alkaline (TA) degumming process using NaOH is a huge challenge in terms of energy consumption and environmental pollution. An earlier laboratory study initiated a Mg(OH)2-AQ aided alkaline oxidation (MAAO) degumming method, which is of promise as an alternative to TA degumming. In this study, the MAAO degumming was evaluated at an industrial scale. With an increase of the scouring pressure, the difference of fibers located in the inner and outer parts of the ramie cage became successively weak and even faded away, finally resulting in the equivalent residual gum content of 7.3% and unseparated fiber rate of 1.4% for both fibers at 0.6 MPa. Two percent of the 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP) addition in high hardness nature water (60 mg/L for Sichuan, 6 mg/L for Hunan) increased above 70% of fiber tenacity. The MAAO degumming process allowed 80.3% of the ramie fiber yield. The cellulose and hemicellulose retention reached 97.7% and 47.6%, respectively, whereas 90.1% of the gum removal, indicating a robust component selectivity of the MAAO method. The resulting fiber was 6.27 cN / dtex of the tenacity and 64 mm of the length, respectively, which was similar to that of conventional oxidation degumming. Remarkably, the MAAO degumming process consumed 33% less water and 50% shorter degumming time, and discharged 21.4% less total COD, than the TA degumming did. The MAAO method is of promise to the industrial application of oxidation degumming of ramie.