Abstract
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%).
Highlights
Introduction published maps and institutional affilZeolites are hydrated aluminosilicates of metals from the I and II group, formed in hydrothermal processes of rock transformation in the environment or synthesized by chemical methods
Na-X was obtained from a waste solution rich in silicon and aluminum (formed during the synthesis of Na-X(C)) according to the procedure contained by Panek et al [18]
Due to the larger specific surface area of Na-X, the ion adsorption is more efficient on its particles than on the Na-X(C) ones
Summary
In the first stage of the experiment, the zeolite–carbon composite (Na-X(C)) was obtained. Zeolite composite was created in the hydrothermal reaction of fly ash (25 kg) with a 3 M aqueous sodium hydroxide solution (90 L) on the technological line for the synthesis of ash zeolites for 48 h in 80 ◦ C [19]. Na-X was obtained from a waste solution rich in silicon and aluminum (formed during the synthesis of Na-X(C)) according to the procedure contained by Panek et al [18]. This waste solution was mixed with a sodium hydroxide solution containing Al foil and subjected to a hydrothermal reaction. Mineralogical, structural and textural characteristics were conducted on both sorbents
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
