Abstract
In this work, the efficiency of the adsorptive removal of the organic cationic dye methylene blue (MB) from polluted water was examined using three materials: natural clay (zeolite), Zn-Fe layered double hydroxide (LDH), and zeolite/LDH composite. These materials were characterized via X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray (EDX) diffraction (XRF), low-temperature N2 adsorption, pore volume and average pore size distribution and field emission scanning electron microscopy (FE-SEM). The properties of the applied nanomaterials regarding the adsorption of MB were investigated by determining various experimental parameters, such as the contact time, initial dye concentration, and solution pH. In addition, the adsorption isotherm model was estimated using the Langmuir, Freundlich, and Langmuir–Freundlich isotherm models. The Langmuir model was the best-fitting for all applied nanomaterials. In addition, the kinetics were analyzed by using pseudo-first-order, pseudo-second-order, and intraparticle diffusion models, and the pseudo-second-order model was an apparent fit for all three applied nanomaterials. The maximum Adsorption capacity toward MB obtained from the materials was in the order zeolite/LDH composite > zeolites > Zn-Fe LDH. Thus, the zeolite/LDH composite is an excellent adsorbent for the removal of MB from polluted water.
Highlights
IntroductionPublisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations
The equilibrium was investigated using isotherm models and discussed in terms of its nonlinear equations; we proved our results by examining the statistical parameters R2, adjusted R and χ2 as shown in Equations (3)–(5): χ2 = ∑2 /qcal 2 (3)
All reagents used in the experiments were of high analytical grade, and analytical precision in dye measurement was ensured by measuring methylene blue (MB) solution standard with the UV–vis spectrophotometer to obtain a calibration curve with R2 = 0.999
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Large quantities of harmful dyes have been used in various industries, such as in pharmaceutical products, textiles, leather, cosmetics, food, and paints [1]. More than 10,000 types of organic dyes used in industry are discharged as effluents into the environment, causing harmful pollution [2,3,4]. Synthetic dyes are difficult to biodegrade and cause severe public health concerns, even at low concentrations [5]. Alternative techniques for removing dyes from wastewater are needed to decrease pollutant concentrations to acceptable levels
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