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.