Determination of trace levels of uranium in waste solutions by energy dispersive X‐ray fluorescence following adsorption on graphene oxide

Abstract

This paper proposes a rapid X-ray fluorescence (XRF)-based screening method for the determination of trace uranium in solutions. In this method, uranium present in a solution was adsorbed onto graphene oxide (GO), which was collected and subjected to XRF analysis. Upon increasing the sodium ion concentration, the aggregation of GO was promoted, facilitating its collection. Since the GO-collecting membrane filter was significantly larger than the X-ray irradiation field of the XRF spectrometer, it was folded to 1/3 of its original length and width. The folded membrane filter was sealed to prevent uranium from

X-ray-Fluorescence-Based Screening Method for Uranium in Contaminated Brackish Water Using Graphene Oxide Nanosheets

“…A GO nanosheet (size ~600 nm, 4 mg mL −1 , dispersed in H 2 O, Merck & Co., Inc., Rahway, NJ, USA) was used to adsorb uranium. Similarly to our previous studies [ 17 , 22 , 23 , 24 ], the multielement standard XSTC-1407 (Spex CertiPrep Inc., Metuchen, NJ, USA), containing 10 μg mL −1 of each element (Co, Cs, Cu, Th, and U), was employed to adjust the uranium concentration in the standard sample. To obtain the fitting parameter for the Br Kβ peak, a 0.05 mol L −1 bromine solution (FUJIFILM Wako Pure Chemical Corporation, Osaka, Japan) was used.…”

“…The preparation method employed herein was based on our previously reported study [ 17 ], and is summarized in Figure 2 . Initially, sodium perchlorate monohydrate was added to 75, 150, 225, and 300 mL of pure water until the salinity meter reading reached 3% ( n = 6).…”

“…Even though highly saline samples, such as seawater and brackish water, cannot be subjected to analysis by inductively coupled plasma mass spectrometry (ICP-MS) [ 16 ], X-ray fluorescence (XRF) analysis can be employed. Indeed, we recently proposed a new method for the XRF-based analysis of trace uranium in sodium perchlorate aqueous solutions with added uranium [ 17 ]; specifically, we proposed that the uranium present in the sample solution adsorbs onto the surface of graphene oxide (GO) nanosheets in the presence of sodium perchlorate, thereby promoting GO aggregation [ 18 , 19 , 20 , 21 , 22 ] and preventing pore blockage during subsequent sample collection using a membrane filter. Our previous study indicated that the optimal amount of sodium perchlorate resulted in a salinity reading of 3–4% [ 17 ].…”

“…Indeed, we recently proposed a new method for the XRF-based analysis of trace uranium in sodium perchlorate aqueous solutions with added uranium [ 17 ]; specifically, we proposed that the uranium present in the sample solution adsorbs onto the surface of graphene oxide (GO) nanosheets in the presence of sodium perchlorate, thereby promoting GO aggregation [ 18 , 19 , 20 , 21 , 22 ] and preventing pore blockage during subsequent sample collection using a membrane filter. Our previous study indicated that the optimal amount of sodium perchlorate resulted in a salinity reading of 3–4% [ 17 ]. It should be noted that salinity is generally expressed as a dimensionless quantity in permillage; however, the readings of the salinity meter employed in this study are displayed as “% ( w / w )”.…”

“…Subsequently, the correlation between salinity and the signal intensity of the U Lα peak was investigated, and a method was developed to confirm whether the uranium concentration in brackish water increased. In our previous study [ 17 , 22 ], small sample volumes were employed; by contrast, relatively large volumes of brackish water were collected for the current study. Furthermore, we investigated the optimal quantity of dispersed GO required for uranium adsorption.…”