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Bleaching Miscanthus x giganteus Acetosolv pulps with hydrogen peroxide/acetic acid. Part 1: Behaviour in aqueous alkaline media

Department of Physical Chemistry and Chemical Engineering, University of A Coruña, A Coruña, Spain.
Bioresource Technology (Impact Factor: 5.04). 02/2009; 100(20):4731-4735. DOI: 10.1016/j.biortech.2009.04.052

ABSTRACT Miscanthus x giganteus bark samples subjected to fractionation by the Acetosolv process under optimal conditions were bleached using hydrogen peroxide and acetic acid in aqueous media under alkaline conditions. The influence of the main operational variables in the bleaching of Acetosolv pulps of M. x giganteus (i.e. hydrogen peroxide concentration, 3–7%; temperature, 55–75 ºC; pH 9–11), obtained after treatments, have been assessed on pulp yield, kappa number, viscosity and brightness of bleached pulps. For this purpose, a rotatable and orthogonal second-order factorial design of experiments was used, in order to identify the optimum operating conditions. The obtained empirical mathematical models demonstrate that, in general, the bleaching was efficient, achieving pulps with kappa numbers below 10. The chemical composition and physicochemical properties of the bleached pulps fulfilled the requirements for forthcoming bleaching stages. Moreover, an alkaline extraction stage to eliminate saponifiable groups of Acetosolv pulps was studied, as well as the necessity of use chelating agents in the stage with hydrogen peroxide.

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    • "organic halogen (AOX) during bleaching. Usually, TCF sequences include oxygen, hydrogen peroxide and ozone based stages (Freire et al., 2006; López et al., 2003; Pedrola et al., 2004; Shatalov and Pereira, 2005; Villaverde et al., 2009). "
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    • "In acid medium, peroxyacetic acid, an electrophile, is the main product. In alkaline conditions, the peroxyacetate anion is dominant, and obviously these species will react very differently (Pérez et al., 2006; Jiménez et al., 2008; Villaverde et al., 2009). The aim of this work was to develop a detailed mathematical study of the influence of independent variables in peroxyacetic acid bleaching of Acetosolv M. x giganteus pulps (viz. "
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    ABSTRACT: Miscanthus x giganteus bark samples subjected to fractio nation by Acetosolv process under optimal conditions were bleached using hydrogen peroxide in acetic acid medium. The influences of the main operational variables in the bleaching of Acetosolv pulps of M. x giganteus (i.e. hydrogen peroxide concentration (1,6-8,4%), temperature (48,2-81,8ºC) and pH (1,8-5,2), have been assessed on pulp yield, kappa number, viscosity, saponifiable groups and brightness of pulps. In order to identify the optimum operating conditions, a rotatable and orthogonal second-order factorial design of experiments was used. Results from the fitting experimental data to empirical mathematical models demonstrate that in general the delignification was extensive, and pulps can achieved with kappa number below 15. The chemical composition and properties of the bleached pulps fulfilled the requirements for forthcoming bleaching stages. Moreover, the use of chelating agents in the hydrogen peroxide stage along with the study of pH and time effects outside limits of the experimental design was studied.
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