International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 04 Issue: 07 | July -2017 www.irjet.net p-ISSN: 2395-0072 © 2017, IRJET | Impact Factor value: 5.181 | ISO 9001:2008 Certified Journal | Page 489 Box–Behnken modelling of phenol removal from aqueous solution using Emulsion Liquid Membrane A. Balasubramanian Assistant Professor, Department of Petroleum Engineering, AMET University, Chennai, Tamilnadu, India ---------------------------------------------------------------------***--------------------------------------------------------------------- Abstract - Response surface methodology (RSM) is used to optimize the process parameters for the removal of phenol from aqueous solution of wastewater using emulsion liquid membrane technique. The liquid membrane used was composed of Xylene as the solvent, SPAN-80 as the surfactant and sodium hydroxide as an internal reagent and optimized using Box–Behnken design. The optimum values for these factors were found to be surfactant concentration 3.29 % (v/v), M/I ratio 1.05 (v/v) and E/E ratio 0.474 (v/v). Under optimal conditions, the model predicted a maximum efficiency of 96.79%. The obtained model is highly significant (Fobs ≥ FTabulate and low p-value) with a correlation coefficient of 99.42%. On the other hand, linear, quadratic and interaction terms in this model have the largest statistical effect on the response (confidence level= 99 %). Key Words: Response Surface Methodology, Wastewater Box–Behnken design, Emulsion Liquid membrane, Phenol. 1. INTRODUCTION Phenol is used widely in many industrial processes, such as petroleum refineries, steel plants, and pharmaceutical, coal conversion, chemical and dye industries. They are released in industrial wastewater and domestic water, and may be a threat to human health and aquatic life. Phenols are highly toxic compounds even at low concentrations and the discharge of the wastewater containing phenols is restricted severely and have been listed by US EPA as priority pollutants. Normally, a standard limit of less than 1 ppm is established for the release of phenol; however, several industrial effluents containing phenol concentration up to 6900 ppm. Typical treatment options like biological processes (e.g., activated sludge), activated carbon adsorption, reverse osmosis, ion exchange, coagulation- precipitation, Photo degradation and electro dialysis. However, equipment construction and operation costs could be prohibiting for most of the existing processes especially when these compounds occur at very high concentrations. Removal of phenol from wastewater has been intensively investigated using Emulsion Liquid Membrane (ELM) technique. Phenol removal by ELM has many advantages over other separation methods like high selectivity, extraction – stripping in single stage and low cost of operation. Liquid membrane process incorporates dispersion of an emulsion containing organic membrane and aqueous internal phase in a continuous external phase (W/O/W). The solute penetrates from the external phase to the internal phase through the membrane phase, where it reacts with a stripping agent and converts to a material, which is insoluble in the membrane phase and will be trapped in the internal phase. After the extraction, the emulsion phase is then broken by de-emulsification process and the oil phase is recycled for reusing in the emulsification process [1-11]. Response surface methodology (RSM) is a very useful tool which involves three factorial designs giving number of independent factors and their corresponding relationship between one or more measured dependent responses. RSM uses quantitative data from an appropriate experimental design to determine and then to simultaneously solve multivariate problem. Box–Behnken design is a commonly used protocol of RSM. The advantage of the Box–Behnken design is that only three levels are required to reduce experiments. Furthermore, it is more efficient to arrange and to interpret in comparison than other methods. In this method, linear or quadratic effects of experimental variables construct contour plots and a model equation fitting the experimental data. This facilitates the determination of optimum value of factors under investigation and prediction of response under optimized condition [12-15]. This study is focused on to study the linear, square and interactive effects and to optimize the process parameters such as Surfactant concentration, membrane to internal phase ratio (M/I) and emulsion to an external phase ratio (E/E) using RSM on removal of phenol from synthetic wastewater by ELM. 2. MATERIALS AND METHODS 2.1 Box-Behnken Design Box-Behnken was applied to determine the response pattern and then to establish model using Design Expert Software (Stat-Ease Inc.). Three variables used in this study were Surfactant concentration (X1), M/I ratio (X2) and E/E ratio (X3), respectively, with three levels of each variables, while the dependent variable was the phenol removal. The range and levels of individual variables were given in Table 1. An orthogonal 24 Box–Behnken design with five replicates at the center point, all in duplicates, resulting in a total of 17 experiments were used to optimize the chosen key variables for the removal of phenol. The purpose of the center points is to estimate the pure error and curvature. The experiment design was given in Table 2 along with experimental data and