Removal of acid violet 7 from aqueous solution with polymer matrix composite particles by adsorption and photocatalytic decolorization methods: Isotherms, kinetics, and thermodynamic studies

Abstract

A stable and efficient [m-poly(EGDMA-2-VP)]-TiO2 photocatalyst with magnetically separable UV light activated is synthesised and evaluated for the photodegradation and adsorption of Acid Violet 7 (AV7) dye. The polymer particles synthesised were analysed via Scanning electron microscopy ;(SEM) and energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Brunauer - Emmett - Teller (BET) and Electron spin resonance (ESR) techniques. The pH (3, 5, 7 and 9), polymer amount (0.01-0.09 g), initial dyestuff concentration (30, 50, 100, 200, 300, 400 and 500 mg/L), and temperature (277, 293, 318 and 338 K) parameters affecting the adsorption were investigated. The residual dye concentration was read at 517 nm by using a UV-vis spectrophotometer. The best adsorption efficiency (97%) was achieved with 30 mg/L dyestuff solution and 0.01 gram of the polymer at pH 3 at 65 degrees C. The Langmuir isotherm model and the second-order kinetic model were found to agree very well with the experimental data. According to thermodynamic parameters, the adsorption is endothermic and spontaneous. The photocatalytic decolorization was carried out under 395 nm UV light to increase the remaining dyestuffs in the solution. As a result, 99% efficiency was obtained from the removal of dyestuffs from the aqueous solution. The decolorization mechanism is described by The Langmuir-Hinshelwood (L-H) model. The degradation of AV7 has also been confirmed by COD measurements. A slight, gradual decrease (from 93.03% to 75.93%) in the photocatalytic activity is observed during repeated cycles of degradation experiment. Thus, the [m-poly(EGDMA-2-VP)]-TiO2 polymer particles possesses efficient adsorptivity and photocatalytic property for AV7 degradation. The magnetic properties of the polymer particles eliminate the risk of secondary pollution and easy recovery of the catalyst.