Abstract
Implementation of the "bulk liquid membrane" (BLM) system was investigated in terms of its efficiency for selective removal of heavy metal ions from natural resources and industrial wastewater. In this paper, the removal of lead (II) ions through a liquid membrane system and factors that influence the process were examined. The research was performed using the homemade transport cell. Two organic solvents were used as liquid membranes: 1,2-dichloroethane and chloroform. Metal ion concentration in aqueous phases was monitored by flame atomic absorption spectrophotometry, after 4 hours of experiment. Macrocyclic ether (dicyclohexano-18-crown-6) was used as ligand for Pb (II) ions. The effects of nonionic surfactants (Triton X-100, Triton X-45 and Triton X-405) added in the receiving phase of BLM system were investigated. The results showed significant increase in transport rate compared to systems without surfactants. Considering the surfactant structure, transport rate of Pb (II) ions followed the order: TX-100 >TX-45>TX-405. Presence of TX-100 increased transport of Pb (II) ions up to 78% through chloroform and 58% through 1,2-dichloroethane. Â
Highlights
Possibility for removal of heavy metal ions was investigated by many scientists, considering the high toxicity of these ions for living organisms and their tendency to accumulate in the body
The influence of nonionic surfactants added in the receiving phase of the Bulk liquid membrane (BLM) system, were investigated
Investigation was based on the expectation for the interactions between metal ions and nonionic surfactants to occur at the MP/RP interface, enhancing the release of cations into the RP and increasing the removal rate
Summary
Possibility for removal of heavy metal ions was investigated by many scientists, considering the high toxicity of these ions for living organisms and their tendency to accumulate in the body. The liquid membrane is considered as a green technology due to its green characteristics, such as being eco-friendly and its low consumption of organic solvent (Chang et al 2010). The simplicity of this transport technique is reflected in simultaneous processes of: extraction, diffusion and re-extraction of analyte and attracts great attention among researchers (Shokrollahi et al 2009). The first step is to extract metal ions from the SP to the MP. The receiving phase is required to contain suitable stripping agent for successful re-extraction step. Some significant solvent parameters are given for dichloromethane (DCM), 1,2-dichloroethane (1,2-DCE), nitrobenzene (NB) and chloroform (CH) in Table 1 (Kakhki et al 2011)
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