Sorption equilibrium prediction of competitive adsorption of herbicides 2,4-D and MCPA from aqueous solution on activate
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Sorption equilibrium prediction of competitive adsorption of herbicides 2,4-D and MCPA from aqueous solution on activated carbon using ANN Wladyslaw Kaminski • Krzysztof Kusmierek Andrzej Swiatkowski
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Received: 12 March 2014 / Revised: 7 July 2014 / Accepted: 21 August 2014 / Published online: 6 September 2014 Ó Springer Science+Business Media New York 2014
Abstract The simultaneous adsorption of two herbicides— 2,4-dichlorophenoxyacetic acid (2,4-D) and 4-chloro-2methylphenoxyacetic acid (MCPA)—from their aqueous binary mixtures onto granular activated carbon was studied. The quantities adsorbed were determined by HPLC with UV detection. The experimental data were analysed using the Freundlich adsorption isotherm. The high correlation coefficients indicated that the adsorption equilibrium fitted the Freundlich isotherm well. A multilayer perceptron (MLP) (an artificial neural network model—ANN) was applied to describe the adsorption equilibrium in multicomponent systems. This enabled sorption isotherms to be predicted for all possible combinations of the two herbicides. The experimental results and the calculated data obtained from MLP for the solutions of the individual components and their mixtures suggest that MCPA is better adsorbed onto activated carbon than 2,4-D.
Ce D GAC KF
m M MLP n N P qe
Keywords Chlorophenoxy herbicides Activated carbon Adsorption ANN List of symbols ANN Artificial neural network b1, b2, b3, b4 Biases—the signals shifting according to Fig. 1 (dimensionless) C0 The initial concentration of the adsorbate in solution (mmol/dm3)
W. Kaminski Faculty of Process and Environmental Engineering, Lodz University of Technology, 90-924 Lodz, Poland K. Kusmierek (&) A. Swiatkowski Institute of Chemistry, Military University of Technology, 00-908 Warsaw, Poland e-mail: [email protected]
r2 R2 SBET Sme V Vme Vmi wkj
The equilibrium concentration of the adsorbate in solution (mmol/dm3) 2,4-D; 2,4-dichlorophenoxyacetic acid Granular activated carbon Freundlich constant indicative of the relative adsorption capacity of the adsorbent (mmol/g)(dm3/mmol)1/n The mass of the adsorbent (g) MCPA; 4-chloro-2-methylphenoxyacetic acid Multilayer perceptron Freundlich constant indicative of the intensity of the adsorption (dimensionless) The number of calculated coefficients in MLP network (dimensionless) The number of experimental data, (dimensionless) The amount of solute adsorbed per unit mass of adsorbent at equilibrium (mmol/g) Squared coefficient of determination (dimensionless) Squared correlation coefficient (dimensionless) Brunauer–Emmett–Teller surface area (m2/g) Mesopore surface area (m2/g) The volume of the solution (dm3) Mesopore volume (cm3/g) Micropore volume (cm3/g) Weights of signal between neuron k and j according to Fig. 1 (dimensionless)
1 Introduction The widespread use of pesticides has led to many possible sources of contamination by these compounds in the
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environment. Chlorinated phenoxyacetic acid herbicides, such as 2,4-dichlorophenoxyacetic acid (2,4-D)
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