Development of a nanostructured filter for pyrolysis wax purification: Effects of particulate filter aids

Abstract Wax obtained from the pyrolysis of polyethylene waste can contain inorganic contaminants and must be purified before application. We evaluated different filter aids (perlite, sand, and rice husk ash) for the filtration of a crude wax and a pyrolysis wax through a filter medium that was coated with nylon 6 nanofibers to improve filtration efficiency. We first examined the performance of the filter aids in improving crude wax filtration, with the filtration time, temperature, and pressure held constant at 1 h, 170 °C, and 2.5 bar, respectively. Oily wax was then produced by pyrolysis of high-density polyethylene (HDPE) waste in the temperature range 425⿿475 °C. The best filter aid was perlite, which had a filtrate production rate of 5.47 y 10⿿5 m3/h. The highest oily wax yield (87.8%) was achieved at a pyrolysis temperature of 425 °C. The assembly comprising the filter medium coated with nylon 6 nanofibers plus perlite as a filter aid was most suitable for removing impurities from the oily wax generated by the HDPE pyrolysis as it achieved a purification efficiency of 99.9%.