From Feedstock to Function : Production, Characterization and Stabilization of Colloidal Lignin Particles

Abstract

To stop climate change and the loss of biodiversity on our planet, the usage of mineral/crude oil and highly energy-demanding processes have to be replaced. A renewable feedstock and energy-efficient processes are essential to the conversion of the industry.With the principle of a biorefinery plant, several targets of green chemistry/sustainable technology can be fulfilled. Lignin, as one of the products of a Lignocellulose biorefinery and as a side stream from the pulp and paper industry, has a great potential to replace a variety of products from non-renewable sources or synthetic materials.The qualification to absorb UV radiation and the antioxidant, emulsifying, antibacterial, and antifungal properties of lignin, due to its chemical composition and structure, indicate this biopolymer's capability. The mentioned properties are highly accessible when lignin is precipitated into colloidal particles. However, the structure of lignin is depending on the raw material and the extraction process.The scope of this dissertation is to optimize the production of Colloidal Lignin and to investigate the application of these particles as an emulsifier, UV blocker, and antioxidant in order to replace synthetic and, to some extend, environmentally harmful materials. This work should contribute to find a sustainable production process and suitable applications of colloidal Lignin particles.First and foremost, lignin is dissolved or extracted from lignocellulosic biomass. The dissolution of the Organosolv process consumes large amounts of solvent. These procedures should be optimized in order to use less solvent. Also, the solvent recovery after the precipitation is an important approach regarding a sustainable production plant. The screening and fractionation of different Lignin feedstocks should be performed to ensure consistent quality and properties of the product. Analytical methods like UV spectrophotometry, size exclusion chromatography and ion chromatography are essential to obtain data of the Lignin extracts.Furthermore, the precipitation and the downstream processing should be improved and adapted based on the final application. The goal is to obtain highly concentrated and stable suspensions. A significant step towards sustainable technology is the reduction of the freshwater consumption during the valorisation process in order to economise the whole procedure in an eco-friendly way.To investigate the function of Colloidal Lignin particles as an emulsifier, different oil-in-water (o/w) emulsions will be produced. The evaluation of the stability of these o/w emulsions will be performed by centrifugation at different applied centrifugal forces and the droplet size should be determined.The application of colloidal Lignin particles as an UV-Absorber will be investigated in formulating several emulsions with different fat phases and Lignin concentrations. Furthermore, the SPF boosting effect of colloidal lignin will be investigated by mixing Lignin suspensions with commercial organic and inorganic sun blockers. The sun protection factor can be determined by measuring the UV absorption of an emulsion applied on artificial skin.Additionally, further possibilities to use Colloidal Lignin particles as a sustainable substitute in several fields should be considered.