Interference free ultratrace beryllium determination in alkaline effluents of beryllium processing plants by graphite furnace atomic absorption spectrometry after a novel graphene oxide-assisted dispersive micro solid phase extraction without using a chelating agent

Abstract

A novel graphene oxide (GO) mediated dispersive micro solid phase extraction procedure is developed for the extraction of ultratrace beryllium from effluents of beryllium processing plants. These effluents are alkaline in nature due to the extraction of Be as Be(OH)₂. In this process, GO and 1-octanol are used as micro sorbant and extracting agents, respectively. In alkaline effluents, the negative charges on GO nanosheets help in enhancing the dispersibility and sorption capacity. These highly dispersed GO nanosheets effectively interacted with the targeted Be species instantaneously and Be is sorbed quantitatively from the aqueous phase onto their reactive solubilizing sites. The separation and preconcentration of Be sorbed GO are achieved by reducing its hydrophilicity. This is achieved by the addition of an electrolyte, NaCl, which initiates the cation-induced surface charge neutralization of GO. Due this process the π–π interactions dominate over electrostatic repulsion between GO nanosheets, resulting in coagulation and the formation of bulky GO aggregates. These aggregates are easily extracted quantitatively from the bulk aqueous phase into a small 1-octanol phase through hydrophobic interactions. Ultrasonic back extraction of Be is carried out into dilute nitric acid from 1-octanol. The levels of Be in dilute nitric acid are quantified using GFAAS. Under optimized conditions, the preconcentration factor and limit of detection are 100 and 0.002 ng mL⁻¹, respectively, for 50 mL sample. The recoveries are in the range from 90 to 112% at 50–200 pg mL⁻¹.