Effective Removal of Acetaldehyde Using Piperazine/Nitric Acid Co-Impregnated Bead-Type Activated Carbon oleh Yu-Jin Kang, Yu-Jin Kim, Seong-Jin Yoon, Dong-Jin Seo, Hye-Ryeong Cho, Kyeongseok Oh, Seong-Ho Yoon, Joo-Il Park