Highly efficient extraction of phenolic compounds by use of magnetic room temperature ionic liquids for environmental remediation

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A hydrophobic magnetic room temperature ionic liquid (MRTIL), trihexyltetradecylphosphonium tetrachloroferrate(III) ([3C 6PC 14][FeCl 4]), was synthesized from trihexyltetradecylphosphonium chloride and FeCl 3·6H 2O. This MRTIL was investigated as a possible separation agent for solvent extraction of phenolic compounds from aqueous solution. Due to its strong paramagnetism, [3C 6PC 14][FeCl 4] responds to an external neodymium magnet, which was employed in the design of a novel magnetic extraction technique. The conditions for extraction, including extraction time, volume ratio between MRTIL and aqueous phase, pH of aqueous solution, and structures of phenolic compounds were investigated and optimized. The magnetic extraction of phenols achieved equilibrium in 20min and the phenolic compounds were found to have higher distribution ratios under acidic conditions. In addition, it was observed that phenols containing a greater number of chlorine or nitro substituents exhibited higher distribution ratios. For example, the distribution ratio of phenol (D Ph) was 107. In contrast, 3,5-dichlorophenol distribution ratio (D 3,5-DCP) had a much higher value of 6372 under identical extraction conditions. When compared with four selected traditional non-magnetic room temperature ionic liquids, our [3C 6PC 14][FeCl 4] exhibited significantly higher extraction efficiency under the same experimental conditions used in this work. Pentachlorophenol, a major component in the contaminated soil sample obtained from a superfund site, was successfully extracted and removed by use of [3C 6PC 14][FeCl 4] with high extraction efficiency. Pentachlorophenol concentration was dramatically reduced from 7.8μgmL -1 to 0.2μgmL -1 after the magnetic extraction by use of [3C 6PC 14][FeCl 4]. © 2011 Elsevier B.V.

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Journal of Hazardous Materials

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