Chitosan/MCM‐41 nanocomposites for efficient beryllium separation

Abstract

Chitosan nanoparticles (Ch NPs) with individual particles 10-30 nm in size and average aggregate sizes of 240 nm were prepared via ionic gelation. Ordered mesoporous Mobil Composition of Matter No. 41 (MCM-41) with a surface area of 1590 m 2 /g was prepared via a sol-gel method. The nanocomposites were prepared via the in situ dispersion of MCM-41 in chitosan followed by ionic gelation with a multivalent anion to produce MCM-41-impregnated Ch NPs or via the mixture of dispersed MCM-41 with preprepared Ch NPs to produce Ch NPs supported on MCM-41. The beryllium-uptake efficiency was studied with different pH values, contact times, and initial Be(II) concentrations. The maximum achieved uptake efficiencies of the nanocomposites (95% and 96%) were superior to that of MCM-41 (38%) and higher than that of Ch NPs (90%). The nanocomposite formulas facilitated post-treatment separation while maintaining a high beryllium-uptake efficiency. The Be(II)-uptake process for all of the materials followed the pseudo-second-order kinetic model and both the Langmuir and Freundlich isotherms.

Effect of Titanium Dioxide and Carbon Nanotubes on Polyaniline Nanocomposites for Heavy Metals Removal

“…The interaction between Fe 3+ ions and the basic reactive site in amine and imine functional groups was physi‐sorption interaction. The adsorption of heavy metal ions on the reactive site of PAni/HA/TiO 2 /MWNT is caused by the electrostatic forces between Fe 3+ ions with the partial negative site (δ‐) of nitrogen from amine and imine functional groups along the PAni/HA/TiO 2 /MWNT backbone as shown in Figure . Since the adsorption of Fe 3+ ions is physical interaction, thus the desorption process during recyclability study proved to be more viable and efficient and hence increased the recyclability of the PAni/HA/TiO 2 /MWNT.…”

“…In general, heavy metals removal efficiency by PAni/HA/TiO 2 /SWNT can be affected by ion exchange, redox properties and surface physical adsorption . In this study, the removal efficiency of PAni/HA/TiO 2 /SWNT increased as the atomic weight of the metal ions to be removed decreased.…”

“…In this study, the removal efficiency of PAni/HA/TiO 2 /SWNT increased as the atomic weight of the metal ions to be removed decreased. However, Morsi and Elsabee reported that the removal efficiency of un‐doped pristine PAni increased proportionally to the atomic weight of metal ions concerned . Thus, it is strongly believed that the addition of SWNT into the PAni nanocomposites have created larger surface area with conducting and reactive sites that were capable to adsorb the lighter and lower atomic weight heavy metal ions (Fe: 55.845 amu, 89%) onto its tubular surfaces as compared to those with higher atomic weight (Pb: 207.2 amu, 27%) …”

“…It is observed that 4 hours contact time achieved the highest removal efficiency (94.0%) followed by 2 h contact time (93.5%). Principally, the shorter contact time (2 h) might achieve the lower removal efficiency because of insufficient exposure time for the reactive site along the PAni backbone to interact with Fe 3+ ion …”

“…Thus, 4 h is the optimum contact time for the basic reactive site in amine and imine nitrogen groups of PAni to be saturated with the maximum concentration of Fe 3+ ion, hence achieved the highest removal efficiency. After the optimum contact time, the removal efficiency of PAni/HA/TiO 2 /MWNT eventually decreased from 94 to 86% due to the desorption of Fe 3+ ion from the basic reactive sites of PAni with longer stirring time …”