Rare-earth metal based adsorbents for effective removal of arsenic from water: A critical review

Abstract

Arsenic contamination is a global environmental problem due to arsenic’s high toxicity, bioaccumulation in human body and food chain, and severe carcinogenicity to humans. Development of cost-effective remediation technologies is of importance due to the implementation of stricter regulation for drinking water. This review article focuses on the chemical properties and applications of three rare-earth metals (REMs, lanthanum, cerium, and yttrium) based adsorbents for arsenic removal. Among them, cerium (IV) based adsorbents are more efficient for simultaneous adsorption and oxidization of As(III) from the aqueous solutions, while the yttrium based adsorbents adsorb more arsenic than other REM based adsorbents. A series of studies has demonstrated that higher removal efficiency of arsenic can be obtained by the adsorbents that are fabricated by combination of the REMs with less costly and commonly existing metals such as iron and manganese. Faster adsorption can be achieved by using the REM doped support materials that have larger specific surface areas and greater porosity. Ligand exchange, and surface complexation play key roles in the adsorption. It is concluded that the REM based adsorbents can greatly outperform the conventional metal based adsorbents for the industrial applications of treatment of arsenic containing wastewater.

Abbreviations

• 3-D: Three dimensional; CHT: Chitosan; CNB: cellulose ultrafine nanobioadsorbent; CNT: Carbon nanotube; EDX: energy dispersive X-ray spectroscopy; EXAFS: extended X-ray absorption fine structure spectroscopy; E^o: standard electrode potential; FESEM: field emission scanning electron microscopy; FTIR: Fourier transform infrared spectroscopy; GNP: graphene nano-platelet; GO: graphene oxide; HCO: hydrous cerium oxide; HREEs: heavy rare-earth elements; LREEs: light rare-earth elements; M: metal; Max.: maximum; MCL: maximum contaminant level; PAC: powdered activated carbon; Pu: Pumice; PVA: polyvinyl alcohol; Ref.: Reference; REM: rare-earth metal; Rs: Red scoria; TEM: transmission electron microscopy; USEPA: United States Environmental Protection Agency; XPS: X-ray photoelectron spectroscopy.

KEY WORDS:

• Adsorption
• applications
• arsenic
• ligand exchange
• rare-earth metal
• surface complexation

Acknowledgments

YY and KYK thank National University of Singapore providing President’s Graduate Fellowship for their PhD study. LY and CHW would like to give appreciation to NUS for the 4-year PhD scholarship.

Additional information

Funding

This research project is partially supported by the National Research Foundation, Prime Minister’s Office, Singapore under its Campus for Research Excellence and Technological Enterprise (CREATE) program.