Heavy Metallic and Organometallic Ions Scavenging Using Silica‐Based Adsorbent Functionalized with Ligands Containing Sulfur and Nitrogen Elements

Abstract

A variety of silica-based solid phases, whose surfaces are functionalized with ligands containing sulfur and nitrogen elements, are used as self-supporting adsorbents for environmental remediation evaluation and potential separation application. Each adsorbent is tested for its ability to scavenge five metallic ions: Hg 2+ , Cu 2+ , Cd 2+ , Mn 2+ , Pb 2+ , and two organometallic ions: ethylmercury and phenylmercury, from independent homoionic solutions at both neutral and acidic pH values. The results indicate that the percentage of these ions scavenged by a given adsorbent varies, and is found to be highly related to the structural environment in the vicinity of the sulfur and nitrogen elements on the ligand. It is believed that the scavenging of metallic ions is a result of the complexation formation between the metallic ions and the ligands containing sulfur and nitrogen elements, and is not due to the irreversible association chemistry with the sulfur or nitrogen element itself. In the case of organometallic ions, a p-p interaction is thought to be involved in the adsorption with ligands containing an aromatic moiety in addition to the aforementioned forces. The time needed to reach the maximum percent of adsorption decreases as the amount of adsorbent increases. The longer the adsorption time, the higher percent of ion is removed. Other factors, such as the temperature and the acidity in the liquid phase of the matrix affect the percentage of ions scavenged as well.

Adsorption of Pesticidal Compounds Bearing a Single Carboxyl Functional Group and Biogenic Amines by Humic Fraction-Immobilized Silica Gel

“…Considering the nature of the analyte, the time required to reach the maximum percentage of adsorption decreased as the amount of adsorbent increased. The longer the elapsed time, the higher the percentage of analyte adsorbed as shown in Figure , all of which indicate that the adsorption process, in the case of both pesticidal compounds and biogenic amines, was surface-oriented and similar to that in a previous study . Except for the number of accessible interaction sites on the adsorbent, the viscosity of the liquid phase and the types of interactions between analyte and adsorbent are believed to affect the time required to reach the maximum percentage of adsorption.…”

“…the case of both pesticidal compounds and biogenic amines, was surface-oriented and similar to that in a previous study. 28 Except for the number of accessible interaction sites on the adsorbent, the viscosity of the liquid phase and the types of interactions between analyte and adsorbent are believed to affect the time required to reach the maximum percentage of adsorption.…”

Adsorption of Organophosphate Pesticides with Humic Fraction-Immobilized Silica Gel in Hexane

“…Regarding the variations among other elemental compositions between humic fractions collected under acidic and basic conditions, the possible explanation has been provided elsewhere. 37,41 The percentage of oxygen for the humic fractions collected under acidic conditions was always higher (Table 2), compared to those obtained under basic conditions. Previous studies have indicated that the oxygen elements in HA exist mainly in the form of carboxyl groups determined according to the IR signal intensity.…”

“…In addition, the procedure for its chemical immobilization was efficient and reliable, which was essential for the adsorption evaluation with such a small amount of adsorbent (i.e., 10 mg) in the study. Regarding the variations among other elemental compositions between humic fractions collected under acidic and basic conditions, the possible explanation has been provided elsewhere. , …”

Adsorption and Desorption of Plasticizers with Humic-Fraction-Immobilized Silica Gel in Hexane: A Facile Approach to Pre-concentration

“…The results indicated that the time required to reach the maximum adsorption percentage may shorten as more adsorbent is used in the process (not shown). Furthermore, the low viscosity of hexane, a highly specific interaction resulting from the two functional carboxylate groups of analyte, and a significant interaction enhancement in hexane all contributed to the surface-oriented rapid adsorption, which was 80% complete in less than 40 min. ,,− None of these results was reproducible or observable when using other organic solvents, such as ether, or when performed in an aqueous environment.…”