ORIGINAL PAPER Multivariate curve resolution-alternating least squares (MCR- ALS) and central composite experimental design for monitoring and optimization of simultaneous removal of some organic dyes Behzad Maheri Kalejahi • Morteza Bahram • Abdolhossein Naseri • Siyavash Bahari • Masomeh Hasani Received: 3 April 2013 / Accepted: 8 June 2013 Ó Iranian Chemical Society 2013 Abstract In this work, multivariate curve resolution- alternating least squares (MCR-ALS) has been applied to resolve and study the simultaneous degradation of three toxic organic dyes using Fenton reaction. Second-order kinetic-spectrophotometric data in the simultaneous deg- radation of malachite green, crystal violet and methylene blue were analyzed by MCR analysis to get their concen- tration profiles and calculate their degradation factors. The effect of three parameters (Fe 2? ,H 2 O 2 concentration and initial pH) and their possible interaction in the simulta- neous degradation of mentioned dyes were studied and optimized using experimental design and response surface method. Acquiring second-order data makes possible the analysis and study of the studied dyes in the gray systems which is termed as second-order advantage in the litera- tures. The prominent point of this work is the combination of second-order data and response surface methodology. Keywords MCR-ALS  CCD  Fenton reaction  Removal  Toxic dyes Introduction Synthetic organic dyes are widely used in different indus- tries such as textile dyeing, cosmetic and food [1]. Depletion of wastewaters of such industries at the envi- ronment is highly problematic. In some cases, biodegra- dation of these dyes produces new pollutants [2]. As an example, they can enter to the food chain of human and animals directly or indirectly and can generate several diseases [3]. Therefore, primary treatment of water and wastewaters is necessary before discharging of them at the environment. There are several ways to remove or treat these dangerous materials from wastewaters such as adsorption [4, 5], biological degradation [6], electro chemical process [7, 8] and advanced oxidation processes (AOP) [9, 10]. AOPs are processes based on the generation of the hydroxyl radical (OH), which is a strong oxidant to destruct a wide variety of organic dyes. A special kind of AOP is the Fenton reaction, in which the hydroxyl radical is formed from the reaction between H 2 O 2 and Fe(II) ions. In this process, organic dyes are decomposed mainly to CO 2 ,H 2 O and light weight organic acids [10–12]. Developing an effective and reliable analytical method to monitor the dye concentrations is necessary [13, 14]. In dye degradation studies through advanced oxidation pro- cesses, spectrophotometric techniques are widely used as the monitoring technique because of the cheapness of the instrument, easy interpretation and handling of the spectral data. But, traditional univariate spectrophotometry can only be performed if there are no interferents or there is selective wavelength range for the analyte of interest [15– 17]. For the systems with overlapped spectra, the deter- mination of concentration of each component involved in the mixture is not possible except using multivariate B. M. Kalejahi  M. Bahram (&) Department of Chemistry, Faculty of Science, Urmia University, Urmia, Iran e-mail: m.bahram@urmia.ac.ir A. Naseri Department of Analytical Chemistry, Faculty of Chemistry, University of Tabriz, Tabriz, Iran S. Bahari  M. Hasani Department of Analytical Chemistry, Faculty of Chemistry, Bu-Ali Sina University, Hamadan, Iran 123 J IRAN CHEM SOC DOI 10.1007/s13738-013-0293-6