Introduction
Man’s activities such as industrialization, have led to increase
of heavy metals in the environment and this poses great threat to
humans, as well as the land and sea animals. Complete removal or
reasonable reduction in concentration of heavy metals like mercury,
silver and lead in industrial wastes (both liquids and solids) before
disposal is an eco-friendly practice. Several techniques have been
utilized effectively for remediation of heavy metal contamination; such
techniques include: immobilization, extraction, adsorption, chemical
precipitation, ion exchange, reverse osmosis, electrodialysis,
ultrafiltration, nanofiltration, coagulation, flocculation, floatation,
etc.[1,2].
Enhanced removal of heavy metals can be achieved by functionalization of
the extracting solvent, adsorbent or membrane with a sulfur-containing
group like the thiol moiety. While the exact interactions between
various sulfur functionalities and heavy metals are not clearly
understood, it is generally accepted that sulfur functionality has a
strong affinity for heavy metals[3–7]. Murray et al. [4]
discovered that solid, liquid or gaseous materials contaminated with
heavy metals can be treated by contacting such materials with
thiol-functionalized fatty acid or thiol-functionalized ester of fatty
acids (sulfur-modified bio-oil) for a while, under certain conditions
effective for the sequestration of the metal species by the modified
bio-oil. Before then, several researches [8–11] on heavy metal
remediation have been carried out by treatment with sulfur-modified
agents. Bantchev et al. [12] have effectively synthesized (in
presence of ultraviolet radiation at wavelength, λ < 325 nm)
and characterized thioether-functionalized vegetable oil (TF-VO) and the
molecular composition as well as reaction scheme is as shown in Equation
1 [12].
Vegetable oil + Alkanethiol Thiolated oil (1)
This work is aimed at comparing the selective liquid-liquid sorption
capacities of normal and thiolated: palm oil (PO), palm kernel oil (PKO)
and soybean oil (SBO), respectively, in the extraction of silver ions
from synthetic (self-induced) wastewater. This work is justified by the
fact that it supports a healthy ecosystem. Meanwhile, bio-oil is an
environmentally sustainable and renewable material.