Thermo-catalytic co-pyrolysis of waste plastic and paper in batch and tubular reactors for in-situ product improvement.

In this study, a mixture of waste plastics and papers were pyrolyzed under mild conditions in batch and tubular reactors. The decomposition reactions were enhanced by the use of synthetic zeolite-based catalysts to obtain a higher yield of volatiles and modifying the product composition. Especially the decomposition reactions and the product properties obtained from the different reactors were compared. Gases were analysed by GC-FID and GC-TCD. This fraction contains hydrogen, carbon-monoxide, carbon-dioxide and hydrocarbons. The pyrolysis oils have oxygen-containing compounds, such as alcohols, aldehyde, ketones, carboxylic acids or phenol and its derivative. Not only the reactor configurations but also the catalysts had an effect to the product properties, because the catalysts with alkali characters showed advanced behaviour in the reduction of oxygenated hydrocarbons, while high synthetic zeolite catalysts can increase the saturation and isomerization reactions. The long-term behaviour of the pyrolysis oils was followed by an accelerated aging test at 80 °C till 7 days. The catalysts can effectively reduce the rate of density and viscosity increase during the aging and the alkali catalysts showed beneficial properties in reducing the acidic components. In general, the aging properties were more favorable for pyrolysis oils obtained from the tubular reactor compared with the results in batch reactor.

The stabilization ability of NaA zeolite derived from fly ash for lead and cadmium in soil: Mechanisms and evaluation of effectiveness.

Developing technologies aimed at ecologically restoring is of great significance in addressing the problem of heavy metal pollution. In this study, NaA zeolites (FAZ) originated from fly ash with outstanding performance were prepared by alkali fusion hydrothermal method and used for the solidification and stabilization of heavy metals in soil. After systematic evaluation, it was found that FAZ may lower the leaching concentration of lead (Pb) in soil to <1 mg/kg and increase the stabilization rate of Pb to 80 % in the single Pb-contaminated soil, lower the leaching concentration of cadmium (Cd) in soil to <3 mg/kg and increase the stabilization rate of Cd to 60 % in the single Cd-contaminated soil, and lower the leaching concentration of Pb to 0.15 mg/kg and the leaching concentration of Cd to 0.74 mg/kg in PbCd complex polluted soil. Additionally, Pb stabilization rates reach 60 % and Cd stabilization rates reach 30 %, respectively. Ion exchange is primarily responsible for the adsorption and solidification of Pb and Cd in soil by FAZ. Generally, FAZ has a wide range of applications in the rehabilitation of contaminated soil and significantly lowers the level of heavy metal pollution in soil.

Carbon and zeolite-based composites for radionuclide and heavy metal sorption.

Zeolites have been investigated as sorbents of heavy metals from water. Since graphene oxide was already reported as promising radionuclide sorbent, we developed composite materials containing both a synthetic zeolite (type A, P or Y) and graphene oxide to be multifunctional sorbents. The extension of multifunctionality of sorbents was done by presence of third component, exfoliated graphite, to have additional properties as conductivity. The changing sorption activities of a composite was studied depending on its composition and functional modification. The composites, characterized by X-ray powder diffraction, Raman, FTIR spectroscopy and scanning electron microscopy, were tested for sorption of selected radionuclides (134Cs+, 85Sr2+) and heavy metals (Pb2+, Cd2+). The dependency on composition was found in connection with a high sorption of Pb2+ and Cd2+. Finally, optimized multifunctional sorbents (Gr-GO-COOH-A in ratio 40:40:20 and Gr:GO:A in ratio 25:25:50) were found to keep interesting high sorption activities for heavy metals and radionuclides with good conductivity properties.

Use of Zeolites in the Capture and Storage of Thermal Energy by Water Desorption-Adsorption Cycles.

In this work, four zeolite-bearing materials (three naturally occurring and one of synthetic origin) were considered for thermal energy capture and storage. Such materials can store thermal energy as heat of desorption of the water present therein, heat that is given back when water vapor is allowed to be re-adsorbed by zeolites. This study was carried out by determining the loss of water after different activation thermal treatments, the water adsorption kinetics and isotherm after an activation step of the zeolites, the intergranular and intragranular porosity, and the thermal conductivity of the zeolite-bearing materials. Moreover, the thermal stability of the framework of the zeolites of the four materials tested was investigated over a large number of thermal cycles. The results indicate that zeolite 13X was the most suitable material for thermal energy storage and suggest its use in the capture and storage of thermal energy that derives from thermal energy waste.

Simultaneous Removal of Pb2+ and Zn2+ Heavy Metals Using Fly Ash Na-X Zeolite and Its Carbon Na-X(C) Composite.

Pure zeolite (Na-X) and a zeolite-carbon composite (Na-X(C)) were investigated as adsorbents of heavy metals-Pb2+ and Zn2+ from an aqueous solution. These materials were synthesized from fly ash-a waste from conventional hard coal combustion. Both solids were characterized using XRD, SEM-EDS, nitrogen adsorption/desorption, particle size and elemental composition analyses. The adsorption study was performed at pH 5 in the systems containing one or two adsorbates simultaneously. The obtained results showed that the pure zeolite was characterized by a more developed surface area (728 m2/g) than its carbon composite (272 m2/g), and the mean pore diameters were equal to 1.73 and 2.56 nm, respectively. The pure Na-X zeolite showed better adsorption properties towards heavy metals than its Na-X(C) composite, and Zn2+ adsorbed amounts were significantly higher than the Pb2+ ones (the highest experimental adsorption levels were: for Zn2+-656 and 600 mg/g, and for Pb2+-575 and 314 mg/g, on the Na-X and Na-X(C) surfaces, respectively). The zinc ions are exchanged with the cations inside the zeolite materials structure more effectively than lead ions with a considerably larger size. In the mixed systems, the competition between both heavy metals for access to the active sites on the adsorbent surface leads to the noticeable reduction in their adsorbed amounts. Moreover, the hydrochloric acid was a better desorbing agent for both heavy metals, especially Pb2+ one (desorption reached 78%), than sodium base (maximal desorption 25%).

Different zeolite systems for colon cancer therapy: monitoring of ion release, cytotoxicity and drug release behavior.

Three types of oral administrated micronized zeolites [ZSM-5, zeolite A and Faujasite NaX (ZSM-5, ZA and ZX, respectively)] were prepared as anticancer 5-fluorouracil (5-Fu) delivery systems for colon cancer treatment. They were prepared by economically widespread and cheap natural resource, kaolin, at low temperatures, using microwave advanced tool. The obtained powders were characterized by XRD, SEM/EDX and BET; meanwhile, their degradation was investigated in two gastric fluids; FaSSGF (pH 1.6) and FeSSGF (pH 5), through concentration measurement of their solution disintegrated elemental constituents of Na+, Al3+ and Si4+ ions. Also, the processes of drug release and mechanism in both solutions were investigated. Moreover, the inhibition action of 5-Fu-free and 5-Fu-conjugated zeolites on colon cancer cells (CaCo-2) was estimated. The results showed that, the prepared zeolites possessed high surface areas of 526, 250, and 578 m2/g for ZSM-5, ZA and ZX, respectively. Although, zeolite structures seemed significantly stable, their frameworks seemed more likely reactive with time. The ions and drug release for zeolites occurred in successively two stages and found to be pH dependent, where the drug and zeolite ions were significantly of higher values in the more acidic media of the gastric solution (pH 1.6) than those of the mild acidic one (pH 5). The obtained activity indicated no cytotoxic affinity for all the prepared zeolite types. Accordingly, the synthesized zeolite frameworks are proposed to be of strong potential drug delivery vehicle for the treatment of gastrointestinal cancer.