Abstract
Electrospun polystyrene fibres incorporating potassium salts of pyrazole-1-carbodithioate and imidazole-1-carbodithioate were employed as sorbents for heavy metals from aqueous environments. The equilibrating time, initial metal concentrations and sorbent mass for optimal adsorption were 40 min, 5 mg/ℓ and 8 mg, respectively. The optimal pH for metal ion uptake was between 6.3 and 9.0 and was found to be dependent on the basicity of the ligands. Protonation constants for the ligands in aqueous solutions were determined potentiometrically; pK of the imidazole was 6.82 while that of the pyrazole was 3.36. The efficiencies of adsorption and desorption of metals on the imidazolyl-incorporated sorbents were more than 95%, up to the fifth cycle of usage. The limits of quantification were ≤ 0.0145 mg/ℓ for all the metals. Accuracy of the determinations, expressed as relative error between the certified and observed values of certified reference groundwater samples was ≤ 0.2% with relative standard deviations < 3%. Electrospun polystyrene fibres incorporating imidazoles proved to be efficient sorbents for divalent heavy metal ions in aqueous environments as their efficiencies exceeded those of chitosan microspheres, ion-imprinted composites, amino-functionalised mesoporous materials and most of the biomass-based sorbents previously reported on.Keywords: electrospinning, polystyrene, heavy metals, diazole
Highlights
Heavy metal ions are widespread in the human environment and very often occur, at low concentrations, in surface waters (Akoto et al, 2008)
Their concentrations in environmental samples are low, heavy metal ions tend to bioaccumulate through the food chain (Gundacker, 2000; Pourang, 1995) and exert various health effects in humans and animals
Preliminary experiments showed that a mixture of DMF:THF (4:1 v/v) was a suitable solvent system for dissolving polystyrene into solution
Summary
Heavy metal ions are widespread in the human environment and very often occur, at low concentrations, in surface waters (Akoto et al, 2008). The metal ions adsorbed could be released for quantification by placing the sorbent in an acidic solution. The influence of the initial concentrations of the metal ions was investigated for a range (0–10 mg/l) of standard solutions.
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