Removal of methylene blue from aqueous solutions by adsorption onto chemically activated halloysite nanotubes

Abstract

This study examines the adsorption behavior of methylene blue (MB) from aqueous solutions onto chemically activated halloysite nanotubes. Adsorption of MB depends greatly on the adsorbent dose, pH, initial concentration, temperature and contact time. The Langmuir and Freundlich models were applied to describe the equilibrium isotherms and the Langmuir model agrees very well with experimental data. The maximum adsorption capacities for MB ranged from 91.32 to 103.63 mg·g −1 between 298 and 318 K. A comparison of kinetic models applied to the adsorption data was evaluated for pseudo-first-order, pseudo-second-order, Elovich and intra-particle diffusion equation. The results showed the adsorption process was well described by the pseudo-second-order and intra-particle diffusion mode. Thermodynamic parameters suggest that the adsorption is spontaneous and endothermic. The obtained results indicated that the product had the potential to be utilized as low-cost and effective alternative for dye removal in wastewater.

Properties and applications of halloysite nanotubes: recent research advances and future prospects

“…Synthetic dyes are the most studied organic contaminants using Hal as adsorbent, most likely because they are widely used in various industries such as paper, textile, leather, printing, food, and plastic, and their discharge into water causes serious environmental problem, related to their carcinogenicity or toxicity to aquatic life and human beings . The adsorption of a series of dye molecules, including methylene blue (Zhao and Liu, 2008;Luo et al, 2011;Zhang et al, 2012b), neutral red (Luo et al, 2010), methyl violet , methyl orange Li et al, 2015), and malachite green (Kiani et al, 2011) by Hal has been reported. Generally, the results demonstrated that Hal could be used as an effective low-cost adsorbent for the removal of dye contaminants from wastewater, although the adsorption capacity is relatively low in comparison to other synthetic high surface area adsorbent such as activated porous carbon and mesoporous silica.…”

Thermodynamics of Proton Binding of Halloysite Nanotubes

“…The nontoxicity together with the charge separation and the particular hollow tubular structure of HNTs make this clay mineral very useful for different purposes. For example, HNTs are used as support for different polymerization reactions, for the immobilization of catalysts (enzymes, metal ions, or metal ion complexes), as adsorbent of inorganic and organic contaminants and pollutants in the environmental remediation procedures, as support for drug delivery, as nanocontainers for anticorrosion coating, and so on. ,,,− Several reviews have been published on the different applications of HNTs and all the authors agree that although the tubular structure and the high surface/volume ratio are fundamental characteristics for the versatility of this clay mineral the most important role is played by the charge separation between the inner and the outer surfaces. ,,, …”

Kinetic Analysis of the Adsorption of Ethyl Violet onto Graphene Oxide Sheets Integrated with Gold Nanoparticles

“…A second-order reaction happens when this occurs at low adsorbate/adsorbent ratio and two competing second-order reactions happen at higher adsorbate/selective sorbent ratios [30]. There are numerous examples where the pseudo-2 nd order has been found to fit kinetics data from many dyes sorption works [31][32][33][34][35][36][37][38][39]. However, additional evidence is needed to support this conclusion, such as the evaluation of activation energies obtained by re-running the experiment at various temperatures, and an examination of procedure rates in regards to adsorbent particle size, as well as their reliance on the adsorbent's particle size [40].…”