Surface Interactions and Mechanisms Study on the Removal of Iodide from Water by Use of Natural Zeolite-Based Silver Nanocomposites

Abstract

In this work a natural zeolite was modified with silver following two different methods to derive Ag2O and Ag0 nanocomposites. The materials were fully characterized and the results showed that both materials were decorated with nanoparticles of size of 5–25 nm. The natural and modified zeolites were used for the removal of iodide from aqueous solutions of initial concentration of 30–1400 ppm. Natural zeolite showed no affinity for iodide while silver forms were very efficient reaching a capacity of up to 132 mg/g. Post-adsorption characterizations showed that AgI was formed on the surface of the modified zeolites and the amount of iodide removed was higher than expected based on the silver content. A combination of experimental data and characterizations indicate that the excess iodide is most probably related to negatively charged AgI colloids and Ag-I complexes forming in the solution as well as on the surface of the modified zeolites.

Effect of Exchangeable Ions in Natural and Modified Zeolites on Ag Content, Ag Nanoparticle Formation and Their Antibacterial Activity

“…Although the observed binding energy for Ag 3d was higher than that reported for metallic Ag (368.3 and 374.3 eV for Ag3d 5/2 and Ag3d 3/2 ) and silver oxides (Ag3d 5/2 367.5–368 eV) [ 49 ], we assumed the signals of nanocomposites were due to both species Ag(0) and Ag(I) which was supported by the Auger parameter as well. Peaks of Ag3d 5/2 at 368.5–369.7 eV for Ag–loaded zeolites were also reported in the literature [ 12 , 23 , 50 ]. The small difference between the binding energies of Ag(0) and Ag(I) and the narrow Ag3d peaks made the assignment difficult and ambiguous.…”

“…Natural zeolites are well-known and low-cost exchangers for heavy metal removal from waste waters [ 5 ]. Furthermore, based on the selective adsorption and natural availability of zeolites, investigations have been carried out for many years to explore their application in water treatment [ 6 ], agriculture [ 7 ], pharmaceuticals [ 8 ], and drug delivery [ 9 ] and to enhance their properties, such as adsorbing cations [ 10 , 11 ], anions [ 12 ], and gaseous molecules [ 13 ] as well as catalytic activity [ 14 ]. The sorption properties of natural zeolites can be tailored by modification using chemical reagents (acids, bases, salts) that change the cation transfer ability, porosity and even Si/Al ratio in the zeolite framework that alters the ion-exchange capacity [ 15 , 16 ].…”

Efficacy of a Graphene Oxide/Chitosan Sponge for Removal of Radioactive Iodine-131 from Aqueous Solutions

“…The UV–vis absorption spectra of different NaI concentrations are shown in Figure 6 a. The maximum absorption was found at a wavelength of 226 nm [ 25 ]. A calibration curve was established to determine the concentration of NaI derived from the absorbance by using the regression equation y = 0.7834x + 0.1373, as shown in Figure 6 b.…”

Removal of Cr(VI) from wastewater by silver-loaded natural clinoptilolite

“…wastewater from various industrial activities or of groundwater intended to be brought to domestic water quality. Since the number of studies using Ag + -modified zeolites for removing anionic pollutants is relatively low [23,33], in our opinion, a study on their ability to remove anions deserves the efforts.…”