Fabrication and characterization of micro-porous cellulose filters for indoor air quality control

Micro-porous cellulose filters were fabricated from paper mulberry pulp, which has been used for thousands of years with Korean history. 'Han-ji' is the name of a traditional paper used widely in Korea in construction, textile, craftworks and many household items but before now it has not been used for filtration purpose. Seeking for the utilization of this abundant natural material, this study aims to develop a fabrication process for the traditional paper to be used as a filter for dust filtration, and evaluate the performance by lab-scale experiments. To create pores in the paper, cellulose pulp was pretreated using several methods such as TEMPO oxidation and enzyme hydrolysis, or freeze dried with an alcoholic freezing medium, t-butyl alcohol, instead of water. The filters were characterized and their dust removal performance was tested at a lab scale while also monitoring pressure loss. Chemical oxidation and enzymatic pretreatment were helpful in fabricating a homogeneous filter but would not remove fine-dust particles because of its loose, enlarged pores. The best removal efficiency was observed with filters that were not pretreated but in which water had been exchanged with t-butyl alcohol before freeze-drying. The filter attained a dust removal efficiency higher than 99% over the entire experimental period, with a pressure loss of less than 230 Pa, at a 6.67 (cm3/s)/cm2 air-to-cloth ratio.