Optimization of treating phenol from wastewater through the TiO 2 -catalyzed advanced oxidation process and response surface methodology Camila Oliveira Guimarães & Alexandre Boscaro França & Gisella Rossana Lamas Samanamud & Eduardo Prado Baston & Renata Carolina Zanetti Lofrano & Carla Cristina Almeida Loures & Luzia Lima Rezende Naves & Fabiano Luiz Naves Received: 16 May 2018 /Accepted: 4 April 2019 /Published online: 5 May 2019 # Springer Nature Switzerland AG 2019 Abstract The use of dispersed catalysts in aqueous medium inside reactors in advanced oxidative processes is common among researchers. However, due to the difficult separation of these species after treatment, in many cases, the treatment process is unfeasible. In this context, the main target of the work was the evaluation of degradation of the phenolic solution by ozonation titanium dioxide (TiO 2 /P25), supported on zeolite spheres. The process was investigated through the re- sponse surface methodology (RSM) and optimized by the generalized reduced gradient (GRG) algorithm. The effects of various operating parameters including pH, power ozone (O 3 ) generation, flow rate, and treatment time were investigated, using as a response to removal of chemical oxygen demand (COD). It was made in optimum conditions the ratio of biochemical oxygen demand (BOD)/chemical oxygen demand to check the increasing biodegradability, aiming ozonation as prelim- inary treatment, with the possibility of subsequent bio- logical treatments. There was an increase in this ratio from 0.17 to 0.50 in 48 min, which would facilitate the use of the subsequent biological process. The proposed model showed good fit to the experimental data with R 2 and R 2 adj correlation coefficients of 0.9964 and 0.9932, respectively. Keywords Ozonation . Phenol . AOP . Optimization Introduction High phenol concentrations are commonly found in wastewater of petrochemical refinery processes and cooking plant, from 200 to 1500 mg L -1 (El-Ashtoukhy et al. 2013; Lin et al. 2011). The high toxicity of this compound may cause irreversible damages to human beings as muscle weakness, convulsions, and loss of coordination (Parish 2013). Furthermore, an acute expo- sition may result in blood changes, kidneys, and liver failure and even death (Parish 2013). Due to it, the Environmental Protection Agency (EPA) subject this compound to specific discharge regulations. In mineral and potable water, the concentration of phenol must be lower than 0.5 ppb and regarding wastewater fulfill its content has a limit of 0.5 ppm for surface waters and 1 ppm for the sewerage system (El-Ashtoukhy et al. 2013). Phenolic compounds have several applications Environ Monit Assess (2019) 191: 349 https://doi.org/10.1007/s10661-019-7452-x C. Oliveira Guimarães : A. Boscaro França : E. Prado Baston : R. C. Zanetti Lofrano : F. L. Naves (*) Chemical Engineering Department, Federal University of São João Del Rei, São João Del Rei, MG, Brazil e-mail: fabianonavesengenheiro@ufsj.edu.br G. R. Lamas Samanamud Department of Civil and Environmental Engineering, University of Texas, UTSA, San Antonio, TX 78249, USA C. C. Almeida Loures Department of Mechanical Engineering (DEPMC), Federal Center for Technological Education, Angra dos Reis, RJ, Brazil L. L. Rezende Naves University Center of Lavras, UNILAVRAS, Lavras, MG, Brazil