EFFICIENCY OF THE TRANSFORMATION OF MICROFIBERS INTO CARBON-BASED MATERIALS
Another project objective is to evaluate the yields and quality of the diamonds produced, and the scalability of the synthesis process, starting from the different fractions of microfibers recovered from the filtering system of the washing machine. The main textile microfibres can be catalogued based on the polymer they are made of and are divided into 5 classes based on their composition, respectively:
- Polyester: Trevira Finesse, Diolen® Soft, Fortrel Microspun, DuPont Micromattique, Primabelle, Shingosen
- Nylon: Timbrelle®, Supplex Microfiber, Tactel® Micro, Silky Touch
- Acrylic: Microsupreme
- Cellulose: Lyocell
- Mixed: i.e. based on multiple polymers such as polyester, polyamide and polypropylene.
The carbon yields of the carbonization processes for these polymers are extremely variable, relatively high and ranging between 17-22% for polyester (PET), 40% for Nylon, up to 50-55% for polyacrylonitrile (PAN ). Carbonization conditions can also vary greatly and depend on numerous parameters such as: temperature and pressure of the process, presence of additives and catalysts, purity, shape and origin of the starting material. The high-temperature plasma-activated pyrolysis proposed in this project presents some advantages compared to conventional carbonization techniques: it does not require separation of the microfibers based on their composition, nor their pre-treatment. In fact, the carbon precursor (the microfibre) is transformed by the hydrogen plasma into radicals (CH3), which are mainly responsible for the synthesis of CVD diamond. The work plan includes the evaluation of the diamond yield of microfibers from individual polymers, and in the evaluation of the yield retained by the mechanical filters in real samples (microfibres obtained from the filters of washing machine wastewater). To evaluate the quality of the diamond produced, morphological SEM and structural analyses will be carried out using Raman spectroscopy and X-ray diffraction.
A pilot plant for the synthesis of diamonds is located in the laboratories of the Department of Chemical Sciences and Technologies at Tor Vergata. It has been already used for the transformation of fine powders as reagents in heterogeneous phase: diesel soot powders, polyaromatic and metallorganic compounds were used for the synthesis of diamond and carbon-based nanomaterials. The diagram of the device is shown in the figure below.
Diagram of the transformation system based on thermal pyrolysis in the presence of H-reactive plasma.