Studies on the Potential of Nonmodified and Metal Oxide-Modified Coal Fly Ash Zeolites For Adsorption of Heavy Metals and Catalytic Degradation of Organics for Waste Water Recovery

Abstract

<jats:p>A nanocrystalline zeolite of Na-X type (CFAZ) was synthesized by ultrasonic-assisted double stage fusion-hydrothermal alkaline conversion of lignite coal fly ash. Modified CFAZ with magnetic nanoparticles (MNP-CFAZ) was obtained by adding presynthesized magnetic nanoparticles between the synthesis stages. CFAZs loaded by particles of copper (Cu-CFAZ) and cobalt (Co-CFAZ) oxides were prepared by postsynthesis modification of the parent CFAZ, applying a wet impregnation technique. The parent and modified CFAZs were examined for their phase composition by X-ray diffraction, morphology by scanning electron microscopy, and surface characteristics by N2 physisorption. Comparative studies have been carried out on the adsorption capacity of the starting CFAZ and its derivatives with respect to Cd2+- and Pb2+-ions from aqueous solutions. Adsorption isotherms of Cd2+-ions on the studied samples were plotted and described by the adsorption equations of Langmuir, Freundlich, Langmuir–Freundlich, and Temkin. The best correlation between the experimental and model isotherms for the parent and modified CFAZ was found with the Langmuir linear model, assuming a monolayer adsorption mechanism. Parent and modified CFAZs were also studied as catalysts for heterogeneous thermal Fenton oxidation of methylene blue. At 90 °C, the higher catalytic activity exhibits the nonmodified sample, but with the decrease in temperature to 60 °C, the modified samples are more effective catalysts.</jats:p>

Fly Ash Coated with Magnetic Materials: Improved Adsorbent for Cu (II) Removal from Wastewater

“…The rationale behind this behavior might be related to the aggregation of the magnetic particles once the dose is increased, which consequently leads to the decrease in adsorption capacity. This fact was observed when the fly ash was treated with NaOH and H 2 SO 4 [ 15 , 26 ]. Additionally, other researchers have obtained similar results [ 12 , 24 ].…”

“…Fly ash is preferred as an adsorbent since it is a cheap and highly-available material [ 24 , 25 ]. On the other hand, there are highlights that the presence of fly ash discharged from thermal power plants by the burning of coal represents a big environmental issue [ 26 , 27 , 28 , 29 ]. Unmodified fly ash presents small adsorption capacities.…”

Recent Advances in Magnetic Nanoparticles and Nanocomposites for the Remediation of Water Resources

“…Zeolite formed from fly ash derived from lignite combustion was used by Václaviková et al [87] in a fusion hydrothermal process to add in various types of nanomaterials including magnetic hematite (average size, 10 nm) which formed a magnetic composite. They demonstrated a high surface area of 264 m 2 g −1 though somewhat reduced compared to pure zeolite of 486 m 2 g −1 and showed good adsorption of Cd 2+ and Pb 2+ ions from water (163.7 mg•g −1 for Cd 2+ ).…”

Quasi Natural Approach for Crystallization of Zeolites from Different Fly Ashes and Their Application as Adsorbent Media for Malachite Green Removal from Polluted Waters

“…The fly ash zeolites (FAZ) of FAU type have been broadly studied for gas purification, soil recovery, heavy metal and radioactive species uptake, water softening, desalination and purification, including removal of dyes, microorganisms, and various organic and inorganic compounds [32,33]. In our previous studies, zeolite FAU obtained from lignite FA by two-stage synthesis was successfully applied as a CO 2 adsorbent, catalyst for VOCs degradation, matrix for optical sensor, Fenton-like catalyst for removal of organic contaminants from water, adsorbent for retention of heavy metals and dyes from waste effluents [34]. The obtained results are promising but for applications on an industrial scale the two-stage synthesis would increase drastically the waste processing costs.…”