Organosolv pretreatment for cellulose recovery from sawdust for its ulterior use in membrane synthesis and operation

Abstract

Pinus sp. sawdust was pretreated by the ethanosolv process using AlCl3, FeCl3, and H2SO4 as catalysts in order to be compared with the methods that are traditionally used to recover cellulose. The ethanosolv process was carried out using different catalysts, different processing time (30, 45, and 60 min), and different temperatures (170,180°C) according to a 3 × 3 × 2 full-factorial experimental design. For cellulose recovery, lower times and temperatures produced the highest yields (up to 58% dry based). Acetylation of the lignocellulosic material obtained was done using acetic anhydride and sulfuric acid. The esterification degree (%ED) of the material was measured by saponification and back-titration of the residual NaOH. Values of %ED ranged from 25.62 ± 1.21 to 39.62 ± 1.75 with no significant differences among treatments. The acetylated cellulose was recovered with methylene chloride and membranes were produced by the EP method. In order to characterize the films obtained, FTIR, SEM, and Rheometry analysis were performed. Infrared spectra revealed acetylation. Microscopy evidenced dense materials for all conditions, and membrane thickness was calculated. Membranes with the highest Young modulus (YM = 297.2 Pa) were produced with the chemically pulped cellulose. The membranes obtained are useful for micro- and ultrafiltration processes; a strong correlation in rejection was related with lignin content of the raw acetylated material. Water fluxes ranged from 10.45 to 51.56 L h−1 m−2 bar−1 and calcium rejection values were up to 89.75%.