Breaking forever: Capturing and converting toxic PFAS molecules using coral structured biochars from blade waste

Project Description:

This Research Project is part of the Aura CDT’s Keeping it green: Preserving materials and repurposing waste within the Offshore Wind sector Cluster.

Humans tend to generate and abandon a lot of waste while they innovate. Some of this waste can be easily recycled, others not so much. Although technologies are slowly emerging, biorenewable waste generated by decommissioning wind turbine blades (balsa wood) has a finite life before it naturally decomposes. We can circumvent the natural carbon cycle and add value to our waste, provide a new lease of life whilst limit the release of carbon. This being said, not all waste can be tackled in the same way. Polyfluoroalkyl substances (PFAS) have been used since the 1940s for hydrophobic protection, corrosion and grease-resistant coatings (non-stick coatings on cookware). This family of chemicals are organofluorine derived, containing a large number of fluorine atoms. This functionality is the core reason for their success over the years, however it is also the reason for their all-round stability and inability to biodegrade. This factor has established
PFAS molecules as “forever chemicals” due to their lingering nature. While already banned in areas of Europe and the United Kingdom, the USA will phase out PFAS usage within the next few years. The sudden ban on PFAS production is tied to the toxic nature of the dissolved chemicals in water systems, where exposure has been found to lead to liver and immune system damage, as well as a direct link to many cancers for humans. For marine life, PFAS molecules have been found to hinder the growth and photosynthesis of phytoplankton and the reproduction of zooplankton where it will then bioaccumulate in fish and other aquatic wildlife.

A low carbon solution to yet another human-made problem is through the functionalisation and deployment of photoactive biochars. Here, through pre and post-processing of balsa wood (taken from decommissioned wind turbines), biochars can be produced with a defined pore architecture and expansive surface area, this makes them ideal materials as adsorbents and catalyst supports. By maximising pore volume and available surface area, adsorption sites can be established through the incorporation of nanometallic entities that will respond to ultra-violet light. Degradation of molecules such as PFAS can be induced by photocatalysis; irradiation electron movement on the surface of the metal causing degradation by oxidative and reductive pathways. By dispersing and irradiating photoactive biochars in water, model PFAS compounds will be decomposed. However, the aim here is not a complete decomposition, but the upcycling of PFAS into highvalue molecules, while the fluorine atoms will form hydrogenflouride in water. This is feasible, as the photoactive nanoparticles will introduce an element of controllability. This acidic species will be captured using a Ca(OH)2 additive. The resulting fluorspar (CaF2) will filtered from the water. To prevent further water-based pollution the biochars will all contain magnetic photoactive derivatives. This will allow a simple separation from water using an applied magnetic field, here true recyclability can be monitored where a ‘new forever’ can be established.