Biosorption Of Selenium On Thiolated Eggshell Membrane And Its Applications In Selenium Speciation

Biosorption materials have been widely employed in the fields of sewage treatment and trace heavy metal preconcentration attributed to its low-cost, wide choice of the materials, various functional groups and favorable sorption capacity. Selenium is well-known as an essential element for human health, depending on its concentration and chemical forms. Considering that the content of selenium in real world samples is very low, thus, it is necessary to perform appropriate sample pretreatment in order to provide suitable detection sentivity for the quantification of selenium in environmental and biological samples.Eggshell membranes (ESMs) provide a unique, disulfide bond-rich surface. In this dissertation, thioglycolate reduction was used to generate thiol (-SH) groups on the ESM surface by S-S bond cleavage. The thiol bearing ESMs (TESMs) were characterized by scanning electron microscopy and Raman spectroscopy. The fibrous network structure of the ESM is retained in the TESMs. We have demonstrated that TESMs adsorb both Se(IV) and Se(VI) but by different mechanisms; Se(VI) is retained reversibly possibly via electrostatic interactions while Se(IV) is reduced to Se(0) and deposited on the surface of the TESMs. We thus demonstrate speciation of selenium species, by using samples (a) as such and after prior oxidation to Se(VI),(b) preconcentration on a TESM microcolumn,(c) elution by0.5M HNO3that only elutes Se(VI) and (d) detection by graphite furnace atomic absorption spectrometry. The Se(IV) amount is determined by difference.For a1.0mL sample, the enrichment factor was17.2, the S/N=3detection limit was0.06μg L-1and the precision was3.3%at0.50μg L-1. The linear range was0.25-2.50μg L-1. The procedure was validated by analyzing selenium in certified reference materials of human hair (GBW09101) and rice (GBW10010). We further demonstrate utility by speciation of inorganic selenium in a series of water samples.