LigniOx Lignins as Sustainable Bio-Based Dispersants

Recently, a concept of an alkali-O2 oxidation (LigniOx) process for producing lignin dispersants at a kraft pulp mill has been introduced. The LigniOx process uses O2 gas to increase the anionic charge of lignin and the final oxidised lignin product can serve as a concrete plasticiser or versatile dispersant. Besides kraft lignin, the oxidation has been applied to other lignin by-streams, such as organosolv and hydrolysis lignin, to provide water-soluble anionic lignin dispersants. Anionic dispersants cover most of the dispersant market. Concrete plasticisers are anionic dispersants that disperse cement particles to allow good workability of fresh concrete and ensure good strength properties of the matured concrete. Similarly, anionic dispersants are used in preparing paints and coatings containing a high portion of different inorganic pigments. LigniOx dispersants have been demonstrated to work in these applications. Their performance has been measured to be superior to the commercial lignosulphonate products and even to compete with some of the synthetic superplasticizers. Lately, several novel application areas for LigniOx lignins have been explored. These evaluations include testing of LigniOx lignins as gypsum plasticizer, anti-scaling agent, flotation aid (depressant) and as a component in agricultural products. In addition to the results of concrete studies, results of selected examples of the new end uses of LigniOx lignins will be presented. Furthermore, the biodegradability of LigniOx lignins in soil and aquatic environment was followed by measuring CO2 evolution. Kraft lignin and a lignosulfonate product were tested for comparison. The study indicated that oxidation of lignin increases their biodegradation. Based on an environmental life cycle assessment, the LigniOx product outperformed the fossil-based superplasticiser and polyacrylic acid in several impact categories, including reduced effect on climate change