PhD Student, Indian Institute of Technology Guwahati
Separation of Hexavalent Chromium through Supported Liquid Membrane
The current research mainly dealing with separation of heavy metals (Cr(VI), Zn, Ni etc.) using liquid membrane techniques. Liquid membrane is a homogeneous, thin film of liquid (membrane phase) interposed between two other liquid phases, viz. feed (or source) phase and receiving (or strip) phase. The membrane liquid must be immiscible with feed/receiving phase. Feed phase mainly contain solute which need to be transported across the thin film of liquid membrane to the receiving phase.
Abstract: In this study, a competitive transport procedure was used for transport process of Cr(III), Cu(II), Co(II), Cd(II), Ag(I), Pb(II), and Zn(II) metal cations across bulk liquid membrane (BLM) using phenylaza- 15-crown-5 and cryptand 222 as carriers and dichloromethane (DCM), chloroform (CHCl3), nitrobenzene (NB), 1,2-dichloroethane (1,2-DCE) and CHCl3–NB, DCM–1,2-DCE binary solvent solutions as extracting solvents. Atomic absorption spectrometry was used for determination of the concentration of the studied metal cations in source and receiving phases. The experimental results show that maximum transport rate is for silver(I) cation in the presence of the other metal cations using phenylaza-15-crown-5 as carrier and no transport was observed for the seven metal cations by cryptand 222 in all membrane systems. The effect of various parameters on the transport process was investigated. The effect of solvent on the transport efficiency of silver(I) cation was found to be in the order: NB > DCM > 1,2- DCE > CHCl3. The results also showed that the transport process of silver(I) cation through CHCl3–NB and DCM–1,2-DCE bulk liquid membranes is sensitive to the solvent composition. A non-linear relationship was observed between the transport rate of silver(I) ion and the composition of these binary mixed solvents. The influence of some fatty acids as surfactant in the membrane phase on the transport of the metal cations was also investigated.
Pub.: 25 Oct '15, Pinned: 24 Aug '17
Abstract: Removal of cadmium as a hazardous heavy metal is studied by applying a new design of hybrid cell for liquid membrane process. Tri-iso-octyl amine (TIOA) is used as the carrier in the organic phase. The concentration of cadmium in the samples is measured by atomic absorption spectroscopy. The effect of various parameters including type of supporting membrane, pH of feed and stripping phases, initial concentration of cadmium, carrier concentration, solvent nature, and also organic film resistance on mass transfer rate and removal efficiency are studied. The effect of temperature on mass transfer flux is studied by proposing a prediction model. The optimum carrier concentration is found to be about 0.05 M. The appropriate values of pH for feed and stripping phases are about 3 and 13, respectively.
Pub.: 12 Jan '10, Pinned: 24 Aug '17
Abstract: This work highlights the role of synthetic carrier (ionophore) in the separation of heavy metal ions. A new series of ionophores; 4,4′-nitrophenyl-azo-O,O′-phenyl-3,6,9-trioxaundecane-1,10-dioate (R1), bis[4,4′nitro-phenylazo-naphthyl-(2,2-dioxydiethylether)] (R2) 1,8-bis-(2-naphthyloxy)-3,6-dioxaoctane (R3), 1,11-bis-(2-naphthyloxy)-3,6,9-trioxaunde-cane (R4), 1,5-bis-(2-naphthyloxy)-3-oxa-pentane (R5) have been synthesized and used as extractant as well as carrier for the transport of various metal ions (Na+, K+, Mg2+, Ni2+, Cu2+ and Zn2+) through liquid membranes. Effect of various parameters such as metal ion concentration, ionophore concentration, liquid–liquid extraction, back extraction, comparison of transport efficiency of BLM and SLM and different membrane support (hen’s egg shell and PTFE) have been studied. In BLM ionophores (R2–R5) transport Zn+ at greater extent and the observed trend for the transport of Zn2+ is R2 > R4 > R3 > R5 respectively. Further transport efficiency is increased in SLM. In egg shell membrane ionophores (R2–R5) transport Zn+ due to their non-cyclic structure and pseudo cavity formation while ionophore R1 transports Cu2+ ions at greater extent due to its cyclic structure and cavity size. Among the membrane support used egg shell membrane is found best for the transport of zinc ions because of its hydrophobic nature and exhibits electrostatic interactions between positively charged zinc ions and –COOH group of egg shell membrane. Thus structure of ionophores, hydrophobicity and porosity of the membrane support plays important role in separation of metal ions.
Pub.: 20 Nov '11, Pinned: 24 Aug '17