Valorisation of red gypsum through understanding of structure-processing-property relationships across scales

Effective and consistent filtration of mineral suspensions can be hindered by undesirable rheological effects when moisture content of the mineral phase/s is high. Red gypsum is such a material and is produced when waste sulfuric acid from titanium dioxide manufacture is neutralised with limestone, lime, or a combination of the two. Sustainable utilisation of red gypsum is low and significant volumes are wasted in landfill annually, due to handling difficulties and high levels of impurities. Previous work has focused on elemental and microscopic analysis of red gypsum to suggest potential uses, but there is less understanding of the relationships between the process conditions, structural development of particles, and the resulting performance [1]. In this work, samples of industrial red gypsum will be characterised to investigate particle morphology and the presence, quantity, and state of impurities or additional phases. These will be linked to performance measures based on filtration and rheology to identify potential sources of undesirable behaviour. It is important to understand the level of dewatering of red gypsum that is required to avoid behaviour such as thixotropy, and how the incorporation of this water into the mineral structures makes it difficult to filter. In particular, particle shape and size distributions should be controlled alongside the presence of impurities and additional phases when considering permeation of water through a filter cake, in order to avoid potential build-up of smaller particles or impurities at the filter medium. Replication of the gypsum crystallisation process at the lab scale with increased process control will allow isolated changes in conditions to identify resulting differences in characteristics and performance, a step that is currently not possible at the process scale. Developing an understanding that can lead to improvement in the structural characteristics of red gypsum can contribute to increased utilisation and a reduction in waste of this potentially valuable process by-product.

The CDT in Molecules to Product has the potential to make a real impact as a consequence of the transformative nature of the underpinning 'design and supply' paradigm. Through the exploitation of the generated scientific knowledge, a new approach to the product development lifecycle will be developed. This know-how will impact significantly on productivity, consistency and performance within the speciality chemicals, home and personal care (HPC), fast moving consumer goods (FMCG), food and beverage, and pharma/biopharma sectors.
UK manufacturing is facing a major challenge from competitor countries such as China that are not constrained by fixed manufacturing assets, consequently they can make products more efficiently and at significantly lower operational costs. For example, the biggest competition for some well recognised 'high-end' brands is from 'own-brand' products (simple formulations that are significantly cheaper). For UK companies to compete in the global market, there is a real need to differentiate themselves from the low-cost competition, hence the need for uncopiable or IP protected, enhanced product performance, higher productivity and greater consistency. The CDT is well placed to contribute to addressing this shift in focus though its research activities, with the PGR students serving as ambassadors for this change. The CDT will thus contribute to the sustainability of UK manufacturing and economic prosperity.
The route to ensuring industry will benefit from the 'paradigm' is through the PGR students who will be highly employable as a result of their unique skills-set. This is a result of the CDT research and training programme addressing a major gap identified by industry during the co-creation of the CDT. Resulting absorptive capacity is thus significant. In addition to their core skills, the PGR students will learn new ones enabling them to work across disciplinary boundaries with a detailed understanding of the chemicals-continuum. Importantly, they will also be trained in innovation and enterprise enabling them to challenge the current status quo of 'development and manufacture' and become future leaders.
The outputs of the research projects will be collated into a structured database. This will significantly increase the impact and reach of the research, as well as ensuring the CDT outputs have a long-term transformative effect. Through this route, the industrial partners will benefit from the knowledge generated from across the totality of the product development lifecycle. The database will additionally provide the foundations from which 'benchmark processes' are tackled demonstrating the benefits of the new approach to transitioning from molecules to product.
The impact of the CDT training will be significantly wider than the CDT itself. By offering modules as Continuing Professional Development courses to industry, current employees in chemical-related sectors will have the opportunity to up-skill in new and emerging areas. The modules will also be made available to other CDTs, will serve as part of company graduate programmes and contribute to further learning opportunities for those seeking professional accreditation as Chartered Chemical Engineers.
The CDT, through public engagement activities, will serve as a platform to raise awareness of the scientific and technical challenges that underpin many of the items they rely on in daily life. For example, fast moving consumer goods including laundry products, toiletries, greener herbicides, over-the-counter drugs and processed foods. Activities will include public debates and local and national STEM events. All events will have two-way engagement to encourage the general public to think what the research could mean for them. Additionally these activities will provide the opportunity to dispel the myths around STEM in terms of career opportunities and to promote it as an activity to be embraced by all thereby contributing to the ED&I agenda.