실리콘 코팅한 복합막을 이용하여 톨로엔이나 메탄올 같은 휘발성 유기화합물의 제거 및 회수에 관한 연구를 수행하였다. 사용된 막은 코팅층의 두께가 얇고(~1μm), 지지층의 기고율이 커서 투과저항은 적었으며 코팅층과 지지층은 플라즈마 중합에 의해 결합되어 있어서 높은 압력에도 견딜 수 있었다. Feed의 유속은 60cc/min. 이하일 때 사용된 모듈에 위해 휘발성 유기화합물의 제거율은 96~99%이었으며, feed의 농도가 높을수록 제거율은 더 증가하였다. 이 공정은 휘발성 유기화합물의 농도가 높고 유속이 낮은 흐름을 처리하는데 아주 적합함을 알 수 있었다. 사용된 막을 통한 휘발성 유기 화합물들의 투과도는 4~30 × 10-9gmol/sec · cm2· cmHg 이었고, 질소의 투과도는 3~9 × 10-10gmol/sec · cm2 · cmHg 의 범위에 있었다. 휘발성 유기화합물과 질소의 선택도는 유속과 휘발성 유기화합물의 농도에 따라 톨루엔/질소의 경우 10~55, 메탄올/질소의 경우 15~125의 값을 얻었다.

Common volatile organic compounds(VOCs) such as toluene and methanol were removed successfully from N2 using a novel silicone-coated hollow fiber membrane module. This novel membrane is a thin film composite(TFC) and was highly efficient in removing VOCs selectively from a N2 stream. This membrane had some innate advantages over other silicone-based membrane in that the selective barrier was ultrathin(~1 μm) and the porosity of the polypropylene substrate was high which leads to a low permeation resistance. The substram was very strongly bonded to the coating layer by plasma polymerization and can withstand a very high pressure. A small hollow fiber module having a length of 25cm and 50 fibers could remove 96~99% of toluene as well as methanol vapors when the feed flow rate was up to 60cc/min. The percent removal of VOCs were even higher when the feed inlet concentration was higher. This process is especially suitable for treating streams having a low flow rate and high VOCs concentration. The permeances of VOCs through this membrane was in the range of 4~30 × 10-9gmol/sec · cm2· cmHg for both toluene and methanol, and nitrogen permeance was between 3~9 × 10-10gmol/sec · cm2 · cmHg . High separation factor between 10~55 for toluene/N2 and 15~125 for methanol/N2 were obtained depending on the feed flow rate ranges and feed VOCs concentration levels.

• Cha JunSeok(국립환경연구원 대기연구부 대기화학과) | 차준석