Efficient adsorption of multiple heavy metals with tailored silica aerogel-like materials

ABSTRACT

Recently developed tailored adsorbents for heavy metal uptake are studied in batch tests with Cu, Pb, Cd, Ni, Cr and Zn, in order to decontaminate polluted environments where these heavy metals are found in solution – water courses and groundwater. The adsorbents feature mercapto or amine-mercapto groups that are capable of complexating the cations. Through the use of equilibrium tests it is found that a remarkably high heavy metal uptake is obtained for all metals (ranging from 84 to 140 mg/g). These uptake values are quite impressive when compared to other adsorbents reported in the literature, which is also due to the double functionalization present in one of the adsorbents. For the best adsorbent, adsorption capacities followed the order Cu(II) > Pb(II) > Zn(II) > Cr(III) > Cd(II) > Ni(II). With these adsorbents, the removal process was fast with most of the metals being removed in less than 1 h. Competitive sorption tests were performed in tertiary mixtures that were based on real world polluted sites. It was found that although competitive sorption occurs, affecting the individual removal of each metal, all the cations in solution still interact with the adsorbent, achieving removal values that make this type of material very interesting for its proposed application.

GRAPHICAL ABSTRACT

KEYWORDS:

• Heavy metals
• adsorption
• amine
• mercapto
• co-precursor method
• aerogel-like materials

Acknowledgements

The authors acknowledge Prof. Artur Valente, of the Department of Chemistry of University of Coimbra, for the fruitful discussion on the adsorption mechanisms.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

Work developed under the project ‘AeroMCatch – Silica Aerogels for Remediation of Soils Contaminated with Heavy Metals’ (Process No. 141735), by João Vareda and University of Coimbra, funded by Calouste Gulbenkian Foundation (Portugal), through the ‘Programa de Estímulo à Investigação 2015’.