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BACKGROUND Organoperoxyl radicals generated from unsaturated fatty acids can initiate lignin degradation reactions. RESULTS Manganese peroxidase (MnP, EC 1.11.1.13) produced by the basidiomycete Ceriporiopsis subvermispora and biomimetic systems were explored to produce organoperoxyl radicals for lignin degradation of eucalypt wood and unbleached kraft pulps. Treatment of milled-wood with MnP–, Mn3+– or Fe2+–linoleic acid systems transformed the lignin structure and released water-soluble low molar mass aromatic fragments. Lignin transformations initiated by MnP were the most intense. Residual lignins from MnP- or Mn3+-treated wood exhibited diminished yields for thioacidolysis monomers and increased carboxyl content, suggesting β-O-4 and Cα–Cβ cleavage followed by side chain oxidation. MnP-based biobleaching of eucalypt kraft pulp corresponded to savings of 3.7 kg ClO2 ton−1 pulp during elemental chlorine free (ECF) bleaching to 88–90% brightness. Another interesting characteristic of the MnP-treated pulp was a slightly higher drainage before refining, suggesting that this pulp would require less energy during drying in industrial processes. CONCLUSION Lignin was degraded in vitro by the action of MnP and biomimetic systems initiating lipid peroxidation reactions. Application of the most reactive system, based on MnP, provided savings of 3.7 kg ClO2 ton−1 pulp during ECF bleaching to 88–90% ISO brightness. © 2015 Society of Chemical Industry

BACKGROUND Electrochemical advanced oxidation processes (EAOPs), particularly those based on either cathodic electrogeneration of H2O2 or anodic oxidation (AO) via •OH, have become attractive technological options for the complete detoxification of wastewaters. Their integration with separation pre-treatment such as ultrafiltration (UF), nanofiltration (NF) or reverse osmosis (RO) may be a plausible way to reduce processing time and costs. RESULTS Raw effluents from the acid and alkaline elemental chlorine free bleaching stages of a hardwood-based kraft pulp mill, as well as their UF, NF and RO permeates, have been characterized and then treated by AO-H2O2 in a tank reactor with an air-diffusion cathode, which allowed efficient reduction of O2, and a DSA-RuO2 or BDD anode at constant cell voltage (2–12 V). Due to the complexity of the matrix, a larger H2O2 accumulation in the acid effluents was observed. DSA favoured the accumulation of ions, whereas BDD allowed their further transformation into owing to the larger oxidizing power of its physisorbed •OH. The contribution of this species, along with H2O2 and active chlorine, accounted for the significant TOC abatement reached in the different individual and coupled treatments. CONCLUSIONS AO-H2O2 and UF/AO-H2O2 yielded similar mineralization levels (65–68%) for acid effluents, but lower energy consumption (EC) resulted in the latter process due to the lower conductivity of the permeates. NF/AO-H2O2 coupling yielded the largest mineralization of alkaline effluents (96% instead of 75% obtained by AO-H2O2) with low EC. © 2014 Society of Chemical Industry

BACKGROUND: The process of chemical pulp bleaching is based for the most part in chlorine dioxide within elemental chlorine free (ECF) technologies. The use of greener alternatives such as bleaching with hydrogen peroxide (P stage) is not widely used owing to selectivity concerns related to transition metal-catalyzed decomposition reactions. Even at the final stage where peroxide is recognized to boost brightness and improve the brightness stability of the bleached pulp, cellulose degradation often overcomes these advantages. This paper presents the results of studies intended to optimize final peroxide bleaching performance considering two standard ECF industrial bleaching sequences: the conventional DED and the ECF-light OQ(PO)D (stages name: D—chlorine dioxide; E—alkaline extraction; O—oxygen; Q—chelation, (PO)—hydrogen peroxide pressurized with oxygen). RESULTS: The addition of sodium diethylenetriaminepentaacetate (DTPA) was the most effective option in terms of DED pulp bleachability and selectivity with hydrogen peroxide, as well as in terms of brightness reversion. As regards the OQ(PO)D pulp, a blend of DTPA and magnesium was the most beneficial in those properties. CONCLUSIONS: The choice of the best hydrogen peroxide stabilizer, among the different tested combinations of magnesium and chelants (EDTA and DTPA) studied, in terms of pulp bleachability, bleaching selectivity and brightness reversion is dependent on the impact of the previous bleaching stages on metallic nature and content. The pulp Mg/(Fe + Cu) ratio was highlighted as a process parameter controlling cellulose degradation in peroxide bleaching. Copyright © 2010 Society of Chemical Industry