Ammonium removal from aqueous solution by zeolite X synthesized from halloysite mineral

Abstract

Zeolite X was successfully synthesized from natural halloysite mineral by hydrothermal method. The synthesized zeolite X was characterized by XRD, SEM, TEM and HRTEM. The characterization indicated that zeolite X had high crystallinity together with symmetrical and uniform pore channels. Ammonium (NH₄+) adsorption properties of zeolite X were studied using batch experiments. The results revealed that high initial concentration and low temperature favored NH₄+ adsorption on zeolite X. Both Langmuir and Freundlich isotherms fit well with the equilibrium data. Kinetic studies showed that the adsorption followed pseudo-second-order model. Intra-particle diffusion analysis demonstrated that NH₄+ diffused quickly among the particles at the initial 20 min of the adsorption process, and then the diffusion slowed down and stabilized. Thermodynamic parameters such as change in free energy (ΔG⁰), enthalpy (ΔH⁰) and entropy (ΔS⁰) indicated that the adsorption was spontaneous and exothermic at ambient conditions. The reusable ability of zeolite X was also evaluated. Due to its low cost, high adsorption capacity and fast adsorption rate, zeolite X synthesized from halloysite could be used as an effective and environmental-friendly adsorbent for NH₄+ removal.

Assessment of the Biosorption Characteristics of a Spent Cottonseed Husk Substrate for the Decolorization of Methylene Blue

“…The third is the final equilibrium stage when intra‐particle diffusion becomes slower due to the extremely low adsorbate concentration left in the solution. One or more of the three steps control the total adsorption rate 25. Similar conclusion was found in the literature on the adsorption of Neutral Red from aqueous solution onto halloysite nanotubes 26.…”

Synthesization, Characterization, and in Vitro Evaluation of Cytotoxicity of Biomaterials Based on Halloysite Nanotubes

“…Halloysite nanotubes (HNTs) have been recently used due to their unique properties such as their hollow tubular structure, high surface area, surface characteristics, and high biocompatibility [1,2,3,4,5,6]. HNT tubules consist of a two layered aluminosilicate clay (Al 2 Si 2 O 5 (OH) 4 ∙2H 2 O) with an external diameter of 50–80 nm, lumen diameter of 10–15 nm, and length of 1000 nm [7].…”

“…The tubes have multilayer walls with positively charged Al–OH functional groups on the inner surface, and with negatively charged Si–OH functional groups on the outer surface [8]. These characteristics make HNTs a great absorbent for both cationic and anionic molecules [1,2,3,4,5]. Furthermore, their nanosized lumen enables entrapping a range of active agents such as macromolecules, and proteins [9].…”

Synthesization, Characterization, and in vitro Evaluation of Cytotoxicity of Biomaterials based on Halloysite Nanotubes

“…Halloysite nanotubes (HNTs) have been recently used due to their unique properties such as their hollow tubular structure, high surface area, surface characteristics, and high biocompatibility [1][2][3][4][5][6]. HNT tubules consist of a two layered aluminosilicate clay (Al2Si2O5(OH)4·2H2O) with an external diameter of 50-80 nm, lumen diameter of 10-15 nm, and length of 1000 nm [7].…”

“…The tubes have multilayer walls with positively charged Al-OH functional groups on the inner surface, and with negatively charged Si-OH functional groups on the outer surface [8]. These characteristics make HNTs a great absorbent for both cationic and anionic molecules [1][2][3][4][5]. Furthermore, their nanosized lumen enables entrapping a range of active agents such as macromolecules, and proteins [9].…”