Selectivity assessments of a sequential extraction procedure for potential trace metals' mobility and bioavailability in phosphate rocks from Jordan phosphate mines

Abstract

A modified six-step sequential extraction procedure was used to fractionate and determine the following trace metals: U4+, As5+, Cd2+, Cr+2, Cu2+, Ni2+, Pb2+, Zn2+, and V5+ in three different phosphate rocks from mines in Jordan. The mean values of uranium in the samples investigated were 98 ± 6 mgkg-1, 92 ± 3 mgkg-1, 215 ± 6 mgkg-1, and 159 ± 13 mgkg-1, respectively. The sequential extraction results obtained showed that most of the U4+ in these samples was strongly bound with 87%, 93%, 97%, and 93% of the total content, respectively, remaining in the samples after the sequential extraction steps were performed. Hence, 13%-7% and 3%-7%, respectively, of the U4+ is distributed in the most labile form, indicating that the majority of the U4+ in these samples was highly incorporated within the apatite present in the samples. The aforementioned was in agreement with the XRD and SEM-EDX results obtained. The apparent mobility of U4+, As5+, Cd2+, Cr+2, Cu2+, Ni2+, Pb2+, Zn2+, and V5+ (using all six extraction steps) from the Al-Abied and Al-Hasa samples was as follows: As5+ (30.17%)> Cu2+ (6.55%)> Zn2+(4.34%)> Cd2+ (3.84%) Cr+2 (3.66%)> Pb2+ (2.57%)> V5+ (53%)> Ni2+ (1.71%)> U4+ (0.99%). The mobility of As5+, Cd2+, Cu2+, Cr+2, Ni2+, Pb2+, U4+, Zn2+, and V5+ (using all six extraction steps) from Eshidiya samples was as follows: As5+ (17.32%)> Cr+2 (4.84%)> Zn2+ (4.25%)> Pb2+ (4.19%)> Cu2+ (3.49%)> V5+ (1.42%)> Cd2+ (0.78) U4+ (0.09%)> Ni2+ (0%)