ARTICLE IN PRESS JID: JTICE [m5G;February 25, 2015;20:41] Journal of the Taiwan Institute of Chemical Engineers 000 (2015) 1–7 Contents lists available at ScienceDirect Journal of the Taiwan Institute of Chemical Engineers journal homepage: www.elsevier.com/locate/jtice Optimization of visible-light photocatalytic degradation of acetaminophen by K 3 [Fe(CN) 6 ]-modified TiO 2 Justin Chun-Te Lin a , Mark Daniel G. de Luna b , Mary Jane N. Gotostos b,c , Ming-Chun Lu d,∗ a Department of Environmental Engineering and Science, Feng Chia University, Taichung 407, Taiwan b Department of Chemical Engineering, University of the Philippines, Diliman, Quezon City 1101, Philippines c Department of Chemical Engineering, Mindanao State University, Marawi City 9700, Philippines d Department of Environmental Resources Management, Chia Nan University of Pharmacy and Science, Tainan 717, Taiwan article info Article history: Received 8 July 2014 Revised 3 November 2014 Accepted 30 November 2014 Available online xxx Keywords: Optimization Visible-light photocatalysis Response surface methodology Acetaminophen Box–Bhenken design abstract Visible-light photocatalytic degradation of acetaminophen (ACT), one of the most detected pharmaceuticals in aqueous environment, by K 3 [Fe(CN) 6 ]-modified TiO 2 was presented in this study. Mutlivariate analysis based on response surface methodology was employed to quantify the individual and interaction effects of three key process parameters, i.e. photocatalyst dosage (A), initial ACT concentration (B), and initial pH (C) at pre-determined ranges. Results revealed that among the process variables investigated, initial ACT concentration has the most significant effect, while interactions between photocatalyst dosage and initial ACT concentration (AB) as well as with initial pH (AC) also played important roles. Optimized conditions are obtained at photocatalyst dosage of 0.1 g/L, initial ACT concentration of 0.1 mM, and initial pH of 6.94. The optimized conditions were verified experimentally at 91.06% ACT removal rate, which is within 95% confidence interval of the proposed model. In addition, characterizations of the K 3 [Fe(CN) 6 ]-modified TiO 2 carried out by SEM-EDS, XRD and FTIR provide more structural information for the new visible-light active photocatalyst. © 2015 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved. 1. Introduction TiO 2 photocatalysis is a promising process to be used for environ- mental purification of air and water media [1, 2]. An attractive field of modifying TiO 2 is to extend its photocatalytic activity from UV light (i.e. under 380 nm, which covers about only 5% of the solar spectrum) to visible-light spectrum. Such modification is often carried out by various doping (e.g. metal, non-metal or co-doping of both) to be able to provide advantages such as utilizing solar radiation, operation at ambient temperatures, and the absence of mass transfer limita- tions [3]. However, a number of operational parameters such as TiO 2 loading, pH, temperature, dissolved oxygen, types and loading of con- taminants, light wavelength and intensity, in photocatalytic reactors affect the degradation efficiency of the target pollutants [3–5]. Specifically, for the K 3 [Fe(CN) 6 ]-modified TiO 2 photocatalyst that was used in this study, a previous work determined through a kinetic study done by a conventional one-factor-at-a-time (OFAT) approach that among all the kinetic parameters affecting ACT degradation that was investigated, photocatalyst dosage, initial ACT concentration, and initial pH had the greatest effect on the % ACT removed and the ∗ Corresponding author. Tel.: +886 6 2660489; fax: +886 6 2663411. E-mail address: mmclu@mail.cnu.edu.tw, mclu@ms17.hinet.net (M.-C. Lu). apparent rate constant [6]. Subsequently, optimizing these opera- tional parameters in photocatalytic degradation of ACT is critical in environmental remediation. Furthermore, the development of a model that can quantify individual factor effects and interaction is important for the possible upscaling of the visible light photocatalytic wastewater treatment process. However, due to the complexity and variety of the influencing pa- rameters, conventional one-factor-at-a-time (OFAT) approaches have difficulties to evaluate overall interactions economically and effi- ciently. Statistical designs of experiments (DoE), such as response surface methodology (RSM), not only allow one to quantify the rela- tionships between the desired responses and the different affecting parameters even in the presence of complex interactions, but also to optimize all the affecting variables collectively or to determine a re- gion that satisfies the operating specifications [7,8]. Applying RSM can result in improved product yields, reduced process variability, closer confirmation of the output response to nominal and target require- ments, and reduced development time and overall costs [8]. Three essential steps are involved in this process: (1) perform the random- ized experiments generated by the software to be used; (2) evaluating the coefficients in a mathematical model with response prediction; and (3) examining fit of the model used [9–11]. One of the most common designs in RSM is the Box–Bhenken de- sign (BBD). BBD was devised by George E.P. Box and Donal Bhenken http://dx.doi.org/10.1016/j.jtice.2014.11.030 1876-1070/© 2015 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved. Please cite this article as: J.C.-T. Lin et al., Optimization of visible-light photocatalytic degradation of acetaminophen by K 3 [Fe(CN) 6 ]-modified TiO 2 , Journal of the Taiwan Institute of Chemical Engineers (2015), http://dx.doi.org/10.1016/j.jtice.2014.11.030