Alumina physically loaded by thiosemicarbazide for selective preconcentration of mercury(II) ion from natural water samples

• Published in: Journal of hazardous materials Vol. 156; no. 1; pp. 521 - 529
• Main Author: Ahmed, Salwa A.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15-08-2008; Elsevier
• Subjects: Alumina; Aluminum Oxide - chemistry; Applied sciences; Continental surface waters; Exact sciences and technology; Freshwater; Hydrogen-Ion Concentration; Mercury - isolation & purification; Mercury(II); Natural water pollution; Natural waters; Pollution; Preconcentration; Semicarbazides - chemistry; Sensitivity and Specificity; Spectrophotometry, Atomic; Spectrophotometry, Infrared; Thiosemicarbazide; Water Pollutants, Chemical - isolation & purification; Water treatment and pollution; Africa, Nile R; Thiosemicarbazide; Preconcentration; Mercury(II); Alumina; Natural waters; Ligand; Metal ion; Enrichment factor; Batchwise; Chlorides; Lead; pH; Stream; Selective extraction; Stability; Distilled water; Thermodesorption; Tap water; Uptake; Heavy metal; Iron III; Surveillance; Surface water; Aqueous solution; Sorbent; Mercury; Atomic absorption spectrometry
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2007.12.049

The multifunctional ligand, thiosemicarbazide, was physically loaded on neutral alumina. The produced alumina-modified solid phase (SP) extractor named, alumina-modified thiosemicarbazide (AM-TSC), experienced high thermal and medium stability. This new phase was identified based on surface coverage determination by thermal desorption method to be 0.437
±
0.1
mmol
g
−1. The selectivity of AM-TSC phase towards the uptake of different nine metal ions was checked using simple, fast and direct batch equilibration technique. AM-TSC was found to have the highest capacity in selective extraction of Hg(II) from aqueous solutions all over the range of pH used (1.0–7.0), compared to the other eight tested metal ions. So, Hg(II) uptake was 1.82
mmol
g
−1 (distribution coefficient log
K
d
=
5.658) at pH 1.0 or 2.0 and 1.78, 1.73, 1.48, 1.28 and 1.28
mmol
g
−1 (log
K
d
=
4.607, 4.265, 3.634, 3.372 and 3.372), at pH 3.0, 4.0, 5.0, 6.0 and 7.0, respectively. On the other hand, the metal ions Ca(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Pb(II) showed low uptake values in range 0.009–0.720
mmol
g
−1 (log
K
d
<
3.0) at their optimum pH values. A mechanism was suggested to explain the unique uptake of Hg(II) ions based on their binding as neutral and chloroanionic species predominate at pH values ≤3.0 of a medium rich in chloride ions. Application of the new phase for the preconcentration of ultratrace amounts of Hg(II) ions spiked natural water samples: doubly distilled water (DDW), drinking tap water (DTW) and Nile river water (NRW) using cold vapor atomic absorption spectroscopy (CV-AAS) was studied. The high recovery values obtained using AM-TSC (98.5
±
0.5, 98.0
±
0.5 and 103.0
±
1.0) for DDW, DTW and NRW samples, respectively based on excellent enrichment factor 1000, along with a good precision (R.S.D.% 0.51–0.97%,
n
=
3) demonstrate the accuracy and validity of the new modified alumina sorbent for preconcentrating ultratrace amounts of Hg(II) with no matrix interference.