Preparation and photocatalysis of ZnO/bentonite based on adsorption and photocatalytic activity

Abstract

This article focus on the adsorption and photocataltytic study of methylene blue (MB) dye from aqueous solution with sodium carbonate-activated bentonite adsorbent and ZnO/Bentonite photocatalyst. The activated bentonite adsorbent and ZnO/bentonite nanocomposites photocatalysts were prepared and characterized using XRD, FT-IR, SEM, TEM and AAS. The adsorption experiment was conducted using 5% sodium carbonate activated bentonite (AB5) to establish the effect of different parameters. The adsorption isotherm was performed using Langiumer, Freundlich, and Temkin isotherm models. The result showed the Langiumer adsorption isotherm best fit the adsorption study for the experimental data with R² = 1. The kinetic adsorption of MB dye by activated bentonite was conducted using pseudo-first and pseudo-second-order models. The result revealed that the pseudo-second-order fit experimental data well and the process was chemisorption. The endothermic and spontaneous nature of the adsorption process of MB dye AB5 were carried by studying the thermodynamic parameters of the system. Desorption of MB dye from the spent adsorbent and recyclability of adsorbent was studied by thermo-chemical methods. The desorption capacity of MB dye in the selected solvents were small. The adsorbent developed for this study was recycled and its adsorption capacity decreased with recycling time. But, the photo-degradation studies conducted using the synthesized ZnO/Bentonite@550(1:1) photocatalyst with average particle size of 30.06 nm resulted with 99.54% degradation efficiency of MB.