Delignification of Rice Husk by soda-ethanol-water treatment in light conditions

FELISSIA, FERNANDO ESTEBAN; CHAMORRO, ESTER RAMONA; DAGNINO, ELIANA PAOLA; AREA, MARÍA CRISTINA

Espoo Helsinki

Congreso; IX Iberoamerican Congress on Pulp and Paper Research; 2016

CIADICYP

Lignocellulosic residues can be used as raw material for the production of high value-added products, such as fuel, food additives, cosmetics, adhesives, among many others, in the biorefinery context. Total or partial fractionation of different materials is possible by diverse treatments depending on the material and the desired end product. Argentina has a great variety of natural resources. Among them, rice husks (RH) is a very abundant agroindustrial residue in the northeastern Argentina region. The rice production in Argentina in the 2013/14 campaign reached 1,457,458 tons, of which about 20 % is RH. A combined treatment of dilute acid for hemicelluloses removal followed by a soda-ethanol-water treatment for lignin extraction was applied to rice husk aiming to obtain hemicelluloses, lignin, cellulose and inorganic fractions. Two experimental designs were carried out to evaluate different ranges of the same variables (strong and light conditions), aiming to promote maximal delignification or to delignify while protecting carbohydrates for future uses. Light conditions included 1.9 to 8.0 g/l NaOH and EtOH:H2O ratios of 26:74 to 54:46. All fractionations were carried out in a 180ml AISI 316 stainless steel reactor, heated in a bath of silicon at 160°C for 60 minutes, in a proportion of 10% solids, without agitation. Results were analyzed by multivariate analysis of variance (ANOVA). Statistical analyzes were performed using the software Statgraphics at 95% significance. Acid insoluble lignin concentration (%AIL) remaining in the pretreated solid was determined by NREL/TP-510-42618 and degradation products in the liquid were quantified by HPLC.Lignin in the solid (%AIL on dry original material base) varied between 4.02 and 7.55% in experiments with mean values of EtOH and high and low values of NaOH respectively, with a standard deviation of 0.77%. ANOVA analysis indicated that the %AIL in the studied range only depends on NaOH concentration, whereas yield is function also of the interaction between NaOH and EtOH:H2O. The optimal delignification point was obtained using 8% of NaOH in 54:46 ethanol:water solution. In these conditions, 90.1% of lignin and almost 40% of inorganics were removed from the solid, obtaining a solid rich in cellulose (greater than 70% concentration). Residual AIL was lower than those obtained by other authors using similar treatments with different raw materials. The used soda-ethanol-water process can be defined as a soda process additivated with ethanol, showing significant advantages over soda-anthraquinone process for the fractionation of lignocellulosic materials.