Adsorption of selected oxyanions from aqueous solution using Benzethonium chloride modified zeolite 4A: Artificial neural network approach

Over the years, a wide range of cationic surfactants have been used for the modification of zeolite surface chemistry. In this research study, the synthesized surfactant modified zeolites were characterized using scanning electron microscopy-energy dispersive spectrometry (SEM-EDS), Fourier-transformed infrared spectroscopy (FTIR), Brunauer-Emmet-Teller (BET) and zeta potential analysis. Cr (VI) and Mo (VI). After modification, an increase in Cr (VI) and Mo (VI) oxyanion removal efficiency of zeolite 4A from 22.99 % to 96.3 % and 51.85 %- 85.61 % has been observed. The pore volume diffusion and surface diffusion coefficients Dp and DS were in order of 10-12 cm2 s-1. The mass transfer coefficient Kf were in the order of 10-5 cm s-1. Cr (VI) and Mo (VI) adsorption on BZT-zeolite is good agreement with Langmuir and Sips models. The Cr (VI) and Mo (VI) uptake capacities are approximately equivalent to 3 mg/g. The highest enthalpy changes (Delta H degrees) for the removal of Cr (VI) and Mo (VI) were -105.429 and -53.243 kJ/mol respectively. The entropy changes (Delta S degrees) were -0.335 and -0.163 kJ/mol for the removal of Cr (VI) and Mo (VI) respectively. The free energies of adsorption of Cr (VI) and Mo (VI) were lower than zero. Hence, Cr (VI) and Mo (VI) adsorption process was found to be spontaneous and exothermic. ANN shows excellent modelling for the adsorption process with relatively error values lower than 10 %.