Abstract
A three-dimensional hierarchically structured flowerlike zeolite was synthesized using naturally occurring nanohalloysite (HNT) by hydrothermal methods. Halloysite a hydrated aluminum silicate with nanohollow morphology, microporosity, and environmentally friendly properties was chosen to be the sole precursor. The morphology and structure of the composite that was prepared was characterized using XRD, FT-IR, BET, TG, SEM, HRTEM, and NMR. SEM and HRTEM images indicated that the synthesized zeolite has a flowerlike hierarchical structure, with well-defined edges and uniform pore channels. FT-IR and NMR spectra indicated that different species of silicon and aluminum were present in the synthesized zeolite. The zeolite was applied in fluoride (F-) removal from aqueous solutions. Single-factor studies, including the initial concentration of F-, initial adsorbent concentration, and the effect of pH value on the adsorption properties, were investigated to evaluate the removal behavior of F-by the zeolite. The zeolite exhibited strong adsorption properties for fluoride ions (F-), with an adsorption capacity up to 161 mg g-1. The pseudo-second-order kinetics and Freundlich models were the best fit to the kinetics and isotherm experimental data, respectively.
Highlights
Zeolites are aluminum silicate crystals with a framework structure of three-dimensional tetrahedral units that have abundant micropores with molecular dimensions
The X-ray diffraction patterns of unreacted halloysite powders indicate a d001 peak at 12.1° 2 θ, which corresponds to a basal spacing of 7.3 Å (Figure 1(a), B)
The X-ray diffraction pattern of the halloysite sample shows the occurrence of minor impurities, including characteristic peaks of quartz, gibbsite, and feldspar
Summary
Zeolites are aluminum silicate crystals with a framework structure of three-dimensional tetrahedral units that have abundant micropores with molecular dimensions. This porous crystalline solid has high surface area for unique reactions and adsorption [1]. This combination of properties makes zeolites suitable as adsorbents for a large variety of pollutants. Zeolites are prepared with various silica and alumina sources as a precursor gel under conditions of high pressure and high temperature. An easy and dependable method is ideally required for in situ synthesis of hierarchical structural adsorbents
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