Removal of methylene blue by adsorption on aluminosilicate waste: equilibrium, kinetic and thermodynamic parameters

Abstract

An aluminosilicate waste (AW) was investigated as adsorbent for methylene blue (MB) dye. AW was characterized by petrography, X-ray diffractometry, X-ray fluorescence, scanning electron microscopy, thermogravimetry and zeta potential measurements. It was found that AW contains kaolinite, and other minor components such as quartz, muscovite, smectite, siderite, pyrite and organic compounds. The chemical composition of AW is mainly SiO (49%) and AlO (23%) and it has negative superficial charge above pH 1.73. Adsorption of MB dye was studied in a batch system under different conditions of initial dye concentration, contact time and temperature. The isothermal data from batch experiments were fitted to Langmuir and Freundlich equations, with a better fit shown by the Langmuir isotherm equation. Also, pseudo-first-order, pseudo-second-order and intraparticle diffusion models were considered to evaluate the rate parameters. The experimental data fitted the pseudo-first-order kinetic model best. Thermodynamic parameters were calculated, showing the adsorption to be an endothermic yet spontaneous process, with the activation energy of +37.8 kJ mol. The results indicate that AW adsorbs MB efficiently, and can be employed as a low-cost alternative in wastewater treatment for the removal of cationic dyes.

Methylene Blue Adsorption Study on Microcline Particles in the Function of Particle Size Range and Temperature

“…The estimated values of b are less than a unit, and about the same (0.30−0.32 L mg −1 ) for both particle mass. It can be found in the literature that the adsorption equilibrium of cationic dyes-such as methylene blue-follows the Langmuir isotherm [16,18,25,31,34,36]. Similar results were reported for the adsorption isotherms of various pollutants onto different adsorbent types [21,37].…”

“…However, the percentage removal was higher at a lower concentration, as it has been found by other authors [29,30]. In addition, the initial rate of dye adsorption is greater for higher initial dye concentration because the opposition to the dye uptake reduced as the mass transfer driving force enhanced [29,31]. The initial dye concentration in solution provides an important driving force in overcoming mass transfer resistance between the aqueous and solid phases [31].…”

“…In addition, the initial rate of dye adsorption is greater for higher initial dye concentration because the opposition to the dye uptake reduced as the mass transfer driving force enhanced [29,31]. The initial dye concentration in solution provides an important driving force in overcoming mass transfer resistance between the aqueous and solid phases [31]. In the lower concentrations, all the methylene blue molecules present in the adsorption system are attracted by the unoccupied binding sites, providing higher percentage removal.…”

“…Increasing the concentration, the occupation of available sites increases, until saturation of particle occurs. In the equilibrium condition, both forward and reverse rates must be the same and the concentration remains constant [31].…”

“…With our sorption experimental results, the Langmuir isotherm equation could be applied for analyzing the adsorption equilibrium, as the shape of determined isotherms suggests that. Almeida et al [31] also found that application of the Freundlich model to the experimental data gave a poor fit, so it is inappropriate for the methylene blue/aluminosilicate waste system [31]. According to Yazdani et al [25], the adsorption of Basic Red 18 and Basic Blue 41 onto feldspar followed with Langmuir and extended Langmuir isotherms in single and binary systems [28].…”