6. Exploring the Structural Properties of Membranes used in Lignocellulosic Biorefineries using Ptychotomography

Pulp and paper mills can be converted to lignocellulosic biorefineries that produce pulp, paper, electricity, and novel biochemicals. To achieve this, highly selective separation processes with low-energy demand are required. Membrane processes fulfill these requirements making them an ideal separation technology in a sustainable bioeconomy. However, the unwanted adsorption of compounds to the hierarchical structure of the membrane known as membrane fouling, remains the greatest challenge. Membrane fouling reduces not only the capacity of the filtration process and increases its energy demand, but also increases operational costs and creates a need for chemical cleaning. Conventional analysis techniques such as SEM or AFM can provide information on the foulants attached onto the membrane surface, but the spatial distribution of the foulants inside the membrane structure remains unknown.

This poster presents a study on the spatial distribution of membrane fouling in commercial microfiltration (MF) and ultrafiltration (UF) membranes using ptychographic X-ray computed tomography (PXCT). MF and UF membranes were fouled with process water from thermomechanical pulping, an industrial solution containing hemicelluloses, colloidal wood extractives, and lignin in dissolved and suspended form. PXCT images revealed the fouling layer and its impact on the inner structure of the membrane in 3D. Additionally, membrane cleaning was investigated to understand its impact on the fouling layer and membrane structure. Results from this study provide new insights into the underlying processes leading to adsorption and desorption of compounds onto and from the membrane, ultimately contributing to the development of more efficient and sustainable membrane processes