Synthesis of zeolite NaY and its nanocomposites with chitosan as adsorbents for lead(II) removal from aqueous solution

Zeolites NaY, L and several other zeolites such as NaP, Z, Phillipsite-Na, Perlialite and Fujasite-Na along with orthoclase mineral were synthesized by changing the reaction parameters including the Si/AI ratio, template as well as crystallization temperature, time and status (static or dynamic). Considering the results of 18 and 22 reactions performed for the synthesis of zeolites Land NaY, respectively, it was found that the reaction conditions could strongly affect the product crystal structure and morphology. In addition, some nanocomposites of zeolite with chitosan (CS) and crosslinked CS (CCS) were fabricated containing varying amounts of Y (5-50%). The structural and morphological properties of the zeolites and nanocomposites were analyzed using XRD, SEM, N-2 adsorption-desorption and FT-IR techniques. The average particle sizes measured from the SEM micrographs for the zeolites were changed in the range of 50-100 nm (in Y4 and Y5) to 3-20 mu m (in Y1). Furthermore, the abilities of the zeolites and nanocomposites were evaluated as adsorbents for removal of lead(II) heavy metal ions from aqueous solution. The optimum conditions obtained for the removal of 100 ppm Pb(II) cations using all adsorbents were adsorbent dosage = 10 mg, pH = 6 and contact time = 60 min. The maximum adsorption capacities were obtained equal to 454.5, 54.95 and 24.45 mg g(-1) using the Y, CCS-Y(5%) and CCS, respectively, indicating the adsorption efficacy was varied in the order Y > CCS-Y(5%) > CCS. Kinetics studies proved that Pb(II) adsorption using all adsorbents followed second-order model which illustrated chemisorption of the target analyte was happened on the adsorbent surface. The Langmuir, Freundlich and Temkin isotherms were examined and it was verified that the adsorption data using all adsorbents were well matched to the Langmuir isotherm model. The reusability test certified that all adsorbents preserved more than similar to 92-97% of their original sorption capacities after five cycles of adsorption-desorption experiments demonstrating these are highly beneficial samples for application in the water treatment processes. (C) 2018 Elsevier B.V. All rights reserved.