The aim of our research was to apply experimental design methodology in the optimization of N, N-Dimethyl- 4-nitrosoaniline (RNO, which is indictor of OH radical formation) degradation using gas mixing-circulation plasma process. The reaction was mathematically described as a function of four independent variables [voltage (X1), gas flow rate (X2), liquid flow rate (X3) and time (X4)] being modeled by the use of the central composite design (CCD). RNO removal efficiency was evaluated using a second-order polynomial multiple regression model. Analysis of variance (ANOVA) showed a high coefficient of determination (R2) value of 0.9111, thus ensuring a satisfactory adjustment of the second-order polynomial multiple regression model with the experimental data. The application of response surface methodology (RSM) yielded the following regression equation, which is an empirical relationship between the RNO removal efficiency and independent variables in a coded unit: RNO removal efficiency (%) = 77.71 + 10.04X1 + 10.72X2 + 1.78X3 + 17.66X4 + 5.91X1X2 + 3.64X2X3 - 8.72X2X4 - 7.80X1 2 - 6.49X2 2 – 5.67X4 2. Maximum RNO removal efficiency was predicted and experimentally validated. The optimum voltage, air flow rate, liquid flow rate and time were obtained for the highest desirability at 117.99 V, 4.88 L/min, 6.27 L/min and 24.65 min, respectively. Under optimal value of process parameters, high removal(> 97 %) was obtained for RNO.

Abstract
 1. 서 론
 2. 재료 및 방법
  2.1. 실험재료
  2.2. 분석 및 측정
  2.3. 중심합성설계와 반응표면분석
 3. 결과 및 고찰
  3.1. RNO 분해에 대한 모형 결과 및 잔차분석
  3.2. RNO 분해에 대한 주효과도, 2차원 등고선도 및 3차원 반응표면도
  3.3. RNO 처리율에 대한 공정 최적화
 4. 결 론
 참 고 문 헌

• 김동석(대구가톨릭대학교 환경과학과) | Dong-Seog Kim (Department of Environmental Science, Catholic University of Daegu)
• 박영식(대구대학교 기초교육원) | Young-Seek Park (Faculty of Liberal Education, Daegu University) Corresponding author