Cyanobacterium metallothionein decorated graphene oxide nanosheets for highly selective adsorption of ultra-trace cadmium

• Published in: Journal of materials chemistry 2012-11, Vol.22 (41), p.21909-21916
• Main Authors: Yang, Ting, Liu, Lan-hua, Liu, Jia-wei, Chen, Ming-Li, Wang, Jian-Hua
• Format: Article
• Language: English
• Subjects: Cyanobacteria
• ISSN: 0959-9428; 1364-5501
• DOI: 10.1039/c2jm34712a

Graphene oxide (GO) nanosheets were decorated with a cysteine-rich metal-binding protein, cyanobacterium metallothionein (SmtA). The SmtA-GO composites were characterized by means of FT-IR, AFM and TGA, giving rise to a SmtA binding amount of 867 mg g super(-1). The SmtA-GO composites exhibit ultra-high selectivity toward the adsorption of cadmium, i.e., the tolerant concentrations for the coexisting metal and anionic species were 1-800 000 fold improved after SmtA decoration with respect to bare GO. The SmtA-GO composites were then assembled onto the surface of cytopore microbeads and used for highly selective adsorption and preconcentration of ultra-trace cadmium. In comparison with bare GO (carboxyl-rich GO) loaded cytopore (GO[at]cytopore), SmtA-GO loaded cytopore (SmtA-GO[at]cytopore) shows a 3.3-fold improvement over the binding capacity of cadmium, i.e.7.70 mg g super(-1) for SmtA-GO[at]cytopore compared to 2.34 mg g super(-1) for that by GO[at]cytopore. A novel procedure for selective cadmium preconcentration was developed using SmtA-GO[at]cytopore beads as a renewable sorption medium incorporated into a sequential injection lab-on-valve system, with detection by graphite furnace atomic absorption spectrometry (GFAAS). The cadmium retained on the SmtA-GO surface was eluted with a small amount of nitric acid. An enrichment factor of 14.6 and a detection limit of 1.2 ng L super(-1) were achieved within a linear range of 5-100 ng L super(-1) by using a sample volume of 1 mL. The procedure was validated by analyzing cadmium in certified reference materials and a series of environmental water samples.