A graphene oxide decorated with triethylenetetramine-modified magnetite for separation of chromium species prior to their sequential speciation and determination via FAAS

We describe a fast and sensitive method for sequential speciation and separation of chromium(VI) and chromium(III) using dispersive magnetic solid phase extraction prior to determination by FAAS. The sorbent (mf-GO) was obtained by functionalizing a graphene oxide decorated with magnetite which was modified with triethylenetetramine. The sorbent was characterized by scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray analysis, FTIR and elemental analysis. The use of mf-GO results in fast removal of chromium(VI) (10 min) and of Cr(III) (30 min). The sorption capacity is 16.4 mg∙g‾¹ for Cr(VI) and 9.6 mg∙g‾¹ for Cr(III). Effective chromium speciation is demonstrated by simply tuning the pH value of the solution. Following batch sorption, the particles can be magnetically separated. The method was validated under optimized conditions. Linear dynamic range of calibration plot extends from 5 to 100 μg L⁻¹, and their detection and quantification limits are 1.4 and 4.5 μg L⁻¹ for Cr(VI) and 1.6 and 5.2 μg L⁻¹ for Cr(III), respectively. Accuracy was established by analyzing the SRM JSS (513–4) chromium steel Standard Reference Material. Recoveries of (spiked) analyte range from 96 to 102 %. The method was applied to speciate and quantifies chromium in tannery wastewater, electroplating wastewater, and (spiked) river water. [Figure not available: see fulltext.]