Mercury uptake by biogenic silica modified with L‐cysteine

Abstract

Contaminated sediments provide the main source of mercury for methylation by bacteria in lakes and waterways. In situ capping has been used to remediate these sediments, but traditional reactive materials have very low affinity for Hg(II). This study investigated the mercury uptake by biogenic silica modified with L-cysteine, as a potential material to be used for in situ remediation technologies. The adsorbent was obtained from rice hull ash by extraction as sodium silicate and acid hydrolysis through the sol-gel process; it was then modified with L-cysteine by impregnation from aqueous solution. The unmodified and modified biogenic silica showed structural and chemical properties suitable for mercury sorption from aqueous medium. The cysteine affected the structural properties of the unmodified silica, decreasing the specific surface area and pore volume by eightfold. On the other hand, cysteine increased the silica adsorption capacity, resulting in mercury uptake similar to that of the unmodified silica. The Hg(ll) specific adsorption by unmodified and modified silica was 0.20 mmol/g and 0.19 mmol/g SiO2, respectively, from an aqueous solution of 1 mmol/L Hg(II). The pH range of 3-7did not have an effect on Hg(II) adsorption. However, the presence of chlorine, added as HgCl2, seems to have limited the mercury adsorption, especially at high concentrations of Hg(II). The mercury adsorbed on the silica surface could not be recovered using HCl even from concentrated solutions.

Biosorption of Mercury (II) from Aqueous Solutions onto Fungal Biomass

“…Although the percentage of adsorption decreased, when ions concentration increased. A similar type of trend was reported for the removal of Hg (II) from aqueous solution by sorption on R. oligosporus [21], B. subtilis [24], Pleurotus sapidus [25], biogenic silica modified with L-cysteine [26], and activated carbon prepared from agricultural byproduct/waste [6]. These results may be explained to be due to the increase in the number of ions competing for the available binding sites and also because of the lack of active sites on the biomass at higher concentrations [6].…”

Removal of Hg(ii) in aqueous solutions through physical and chemical adsorption principles

“…Marcia et al fabricated a novel mackinawite modied with L-cysteine as an active adsorbent for Hg(II) removal. 72 Xu et al added Sn and Fe into manganese oxide to obtain a novel Fe-Sn-MnO x composite as an effective adsorbent for capturing mercury from coal-red ue gas through chemical adsorption. 73 The adsorption performance of the composite was remarkably enhanced due to the synergetic effect of Fe-Sn and MnO x .…”

Hybrids and biohybrids as green materials for a blue planet

“…More simply, N-pyrazole could be anchored on a silica gel surface for mercury elimination [69]. A green chemistry route to efficient Hg(II) sorbent was also described using gels obtained from natural silica functionalized with the amino acid L-cysteine [70]. In parallel, some natural products such as tannins were also immobilized over silica beads in order to enhance the material capacity to remove Cr(III) from aqueous solution [71].…”