Surface Chemical Processes under Flow.

Lead Research Organisation: Durham University
Department Name: Chemistry

Abstract

Practical applications that deposit or remove materials from surfaces often occur in a flowing liquid. The liquid applies a shear force to the surface and convection in the liquid can deliver material or reagents to a surface and remove other materials or reaction products. This project aims to understand surface chemical processes that are important in automatic dishwashers, but the insights gained will be relevant to a wide range of practical applications.

The removal of food deposits in dishwashers occurs under conditions of droplet impact (either from primary droplets or from secondary splashes), or under thin-film shear flow as a water sheet drains from a hard surface. The primary mechanism of removal of insoluble deposits is enzymatic digestion by proteases. The wash fluid also contains suspended particulates that must not be redeposited onto surfaces. Today, there is little quantitative understanding of how local hydrodynamics affects, for example, enzymatic digestion of proteinaceous soils or attachment of particles to surfaces.

There are two main aspects to this project.
(i) Development of experimental rigs to mimic the flow conditions occurring in a dishwasher within a cell that has well-controlled hydrodynamics.
(ii) Use of these rigs to study chemical and physical processes occurring on hard surfaces, including the attachment and detachment of particles and the enzymatic removal of a model protein film.

A range of techniques will be employed including high-speed photography and image analysis to determine the flow conditions at surfaces, evanescent wave light scattering to study particle dynamics, evanescent wave spectroscopy to study chemical reactions, and reflectometry or ellipsometry to study swelling of protein films and digestion by an enzyme. Quantitative kinetic models will be developed to reveal the role of local hydrodynamics in physical and chemical processes at surfaces.

Publications

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Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/P510476/1 01/10/2016 30/09/2021
1835436 Studentship EP/P510476/1 01/01/2017 31/05/2021 Walter Hama
 
Description The main aim of the project is to identify the key physical and chemical processes involved in the removal of protein soils from soiled dishware surfaces in automatic dishwashers using enzymes and ultimately construct a model (equation) that describes the cleaning process through the important factors that contribute to the cleaning process. We have used an optical technique to study the cleaning process and discovered that the soil removal process comprises of three steps; (i) swelling of the protein foulants in a liquid environment, (ii) removal at a constant rate, and (iii) fast removal stage. The swelling stage was investigated further and it was found that removal without swelling is difficult. It was also found to be dependent on the liquid environment, i.e. its pH, temperature, and ionic strength. The removal stages (stages (ii) and (iii)) also depend on the aforementioned factors, in addition to liquid flow rates.
Exploitation Route This focus of this research is the removal of protein-based soils from hard surfaces using enzymes. Knowledge gained from this work is applicable to the cleaning of other "hard" surfaces such as floors, kitchen sinks, bathroom tubs and toilets and the cleaning and decontamination of vehicles (also hard surfaces) and surfaces, e.g. roads, that have had toxic waste discharged on them. We have also found the sound understanding of the principles of diffusion in polymers and their subsequent dissolution important in this project and so our findings can be used by others to investigate the diffusion of liquids and other small molecules in polymers, e.g. such as in lithography, and the dissolution of natural polymers, e.g. pulp industry. Lastly, ellipsometry can be used by others, e.g. semiconductor industry, to investigate the properties of surfaces and thin films, either in air or in liquids, like we have done.
Sectors Aerospace, Defence and Marine,Agriculture, Food and Drink,Chemicals,Digital/Communication/Information Technologies (including Software),Education,Electronics,Environment,Healthcare,Manufacturing, including Industrial Biotechology,Pharmaceuticals and Medical Biotechnology,Transport

 
Description The research project is part-funded by Procter and Gamble and some of our findings have been used by the in-house research team at Procter & Gamble in their own research of other issues similar to my project.
First Year Of Impact 2019
Sector Chemicals,Manufacturing, including Industrial Biotechology
Impact Types Economic