Textural properties and adsorption behavior of Zn-Mg-Al layered double hydroxide upon crystal violet dye removal as a...

The preparation of adsorbents plays a vital role in the adsorption method. In particular, many adsorbents with high specific surface areas and unique shapes are essential for the adsorption strategy. A Zn-Mg-Al/layer double hydroxide (LDH) was designed in this study using a simple co-precipitation process. Adsorbent based on Zn-Mg-Al/LDH was used to remove crystal violet (CV) from the wastewater. The impacts of the initial dye concentration, pH, and temperature on CV adsorption performance were systematically examined. The adsorbents were analyzed both before and after adsorption using FTIR, XRD, and SEM. The roughness parameters and surface morphologies of the produced LDH were estimated using 3D SEM images. Under the best conditions (dose of adsorbent = 0.07 g and pH = 9), the maximum adsorption capacity has been achieved. Adsorption kinetics studies revealed that the reaction that led to the adsorption of CV dye onto Zn-Mg-Al/LDH was a pseudo-second-order model. Additionally, intraparticle diffusion suggests that Zn-Mg-Al/LDH has a fast diffusion constant for CV molecules (0.251 mg/(g min^1/2)). Furthermore, as predicted by the Langmuir model, the maximal Zn-Mg-Al/LDH adsorption capacity of CV was 64.80 mg/g. The CV dimensionless separation factor (R_L) onto Zn-Mg-Al/LDH was 0.769, indicating that adsorption was favorable. The effect of temperature was performed at 25, 35, and 45 °C in order to establish the thermodynamic parameters ∆H^o, ∆S^o, and ∆G^o. The computed values indicated exothermic and spontaneous adsorption processes. The study presented here might be used to develop new adsorbents with enhanced adsorption capabilities for the purpose of protecting the water environment.