New polymeric formulations based on lignosulphonates ; Novas formulações poliméricas a partir de lenhossulfonatos

Lignosulphonates (LS) are sulphonated lignin-derived by-products present in sulphite spent liquors (SSL) from acidic sulphite pulping. SSL are mostly burned for inorganic base and energy recovery and considered as underutilized natural resources. The possibility of increasing the company profits with the valorization of LS, through the production of value-added products for different market applications, is highly motivating and is a challenge towards the biorefinery and circular economy concepts. The magnesium-based acidic sulphite cooking process adopted at CAIMA Indústria de Celulose S.A. changed significantly in the last years. Formerly, it aimed at the production of paper-grade cellulosic pulp from eucalypt wood, but nowadays CAIMA produces dissolving pulp from Eucalyptus globulus wood under harsher conditions. Considering that the re-profiling of the sulphite process may have caused inevitable changes in the composition of the final SSL, the first task of this thesis consisted in a systematic chemical analysis to assess the structural features of sulphite spent liquors (SSL) followed by the isolation of LS-rich fractions from SSL yielding purified LS. The chemical composition of SSL showed that more severe pulping conditions led to an increase of volatile compounds, such as acetic acid, methanol and furfural, whilst the amount of dissolved sugars and LS increased less significantly. In turn, the chemical structure of LS, showed that harsher pulping conditions lead to the increase of the molecular weight, degree of condensation and sulphonation degree. The following tasks of the thesis aimed at the development of new formulations based on LS. The second task focused on the chemical modification of LS to improve their performance as plasticizing dispersants in concrete formulations. The first approach consisted on a laccase-catalyzed oxidative treatment of LS targeting the increase of their molecular weight (Mw) and the amount of oxidized groups. The laccase assisted oxidation under optimized conditions (40 ...