- Laboratory of Physical Chemistry and Colloid Science, Wageningen University
- Faculty of Mechanical, Maritime and Materials Engineering, Delft University of Technology
- Faculty of Engineering Technology, University of Twente
The goal of this project is to elucidate the forces and mechanisms of detergent action in particle removal in dry-cleaning with high-pressure carbon dioxide, and to use this insight to give design rules for detergents, a dry-cleaning process and a dry-cleaning apparatus. This goal will be accomplished by a combination of innovative fundamental and practical research. The project consists of three integrated studies; one focuses on the physical chemistry, in the second study mechanical action in dry-cleaning with CO2 is investigated, and the third study involves the development of a model in which the effects of mechanical action and physical chemistry are combined.
Dry-cleaning is a process for removing soils and stains from fabrics and garments that uses a non-aqueous solvent with added detergent. Traditional dry-cleaning method employs organic solvent such as PER (perchloroethylene), which is toxic and environmentally harmful. PER has many adverse effects such as it damages kidneys and liver, and causes gastrointestinal irritation. It can also cause eye, nose and throat irritation. Repeated dermal exposure may result in dry, scale, and fissured dermatitis. If PER is heated sufficiently, thermal decomposition will result in the formation of hydrogen chloride and phosgene gases. Moreover, PER is classified as probably carcinogenic to humans (IARC Group 2A classification). In addition, PER is dangerous to the environment. It is an air pollutant and a groundwater contaminant. There are increasing legal restrictions on the use of PER as well as other conventional dry-cleaning solvents, i.e., chlorinated fluorocarbons and hydrocarbons. As a result, the present research on dry cleaning involves replacement of PER as the dry-cleaning medium and look for an alternative solvent which is environmentally benign, non-toxic, and economical.
Carbon dioxide is non-toxic, non-flammable, ecologically sound, cheap, and available on a large scale. An important difference between dry cleaning with PER or other currently used solvents, and dry-cleaning with CO2 is that carbon dioxide dry cleaning needs a substantially higher pressure (45-60 bar) than atmospheric pressure. Therefore, a new process for dry-cleaning has to be developed. Literature on dry-cleaning using liquid CO2 revealed that removal of small particulate soil (size less than 20 Micron) was inadequate compared to the cleaning performance of PER whereas cleaning of oily soil was comparable or in some cases better than PER. Higher input of mechanical action could not improve the cleaning performance of particulate soil in liquid CO2 and as a result of this the usage of liquid CO2 as a dry cleaning solvent remained limited.