(297d) Opportunities for the Application of Lignin-Derived Macromolecules in Aqueous Systems

Wood consists mainly of cellulose, hemicelluloses, and lignin. In the chemical pulping industry, cellulose and a part of hemicelluloses are converted to various pulp grades as main products. Emerging cellulosic ethanol plants also convert cellulose and hemicelluloses to ethanol as their main product. As a result, lignin has been regarded as an underutilized by-product of the chemical pulping and cellulosic ethanol industries. To improve the financial profit of these processes and prevent a significant loss of resources, value-added products could be produced from lignin. Recently, different methods were developed to generate lignin at commercial scales to facilitate the production of value-added products from lignin. For example, the LignoBoost and LignoForce technologies are commercial processes for producing kraft lignin. Due to the commercial availability of lignin, extensive research has been conducted on producing altered lignin-based value-added products via chemical, electrochemical, thermochemical, and catalytic processes. However, efforts to create value-added water-soluble lignin-based products including dispersants and flocculants, are limited.

Dispersants, emulsifiers, and flocculants are water-soluble chemicals with significant worldwide applications. Dispersants are widely used in the mining and oil industries, and they are applied to reduce the interaction between oil and for enhanced oil recovery applications. In the same vein, they would be used in the flotation process of the mining industry to reduce the viscosity of pulp to have better bobbling performance and ultimately higher recovery yield or be used in cement/concrete as a water retarding agent. Emulsifiers are used to improve the homogenization of oil and water and are extensively used in cosmetic products, e.g., sunscreens and serums. Flocculants are widely used in the mining industry for density control in thickeners or as rheology modifiers in concentrate thickeners. They are used in municipal and industrial wastewater systems worldwide. Commercial dispersants, emulsifiers, and flocculants are mainly oil-based, ineffective, expensive, and non-biodegradable.

Lignin has a three-dimensional structure with several aliphatic and aromatic group attachments, which benefit dispersant/flocculant productions. Lignin can be tailored to have diverse charge densities, molecular weights, and degrees of hydrophilicity, all of which are of significant importance for dispersants/emulsifiers/flocculants. After chemical modification for a dispersant, emulsifier, and flocculant production, lignin-based polymers will inherit some unique features from lignin (e.g., hydrophobicity and three-dimensional structure) that are not available in the currently used commercial flocculants/emulsifiers/dispersants.

In this presentation, the conversion of lignin via grafting, oxidation, polymerization, and nanoparticle production for manufacturing such chemicals will be discussed comprehensively. Also, the fundamental challenges and opportunities in the 1) design of lignin-based water-soluble polymers, 2) interaction of these polymers with constituents of solution/suspensions, and 3) development of processes for the production of lignin-based polymers at a large scale for industrial use will be fundamentally discussed.