Kinetics of transport extraction based on solvent sublation

Abstract

The kinetics of this transport extraction has been studied in a 13112 -N-cetylpyridinium chloride complex pair model system under static conditions with a stagnant aqueous phase and a stationary organic solvent. Using N2 carrier gas at a flow rate of 60 cm3/min, separation efficiencies up to 95% were obtained within 2 hr. with a 400-fold preconcentration of radioiodine into 10 cm 3 of benzene from 4 dm 3 model samples of deionized, tap and river waters. Relevant equations have been derived, from which the separation efficiency, the mass-transfer rate constant and the separation half-time can be calculated in dependence on time for various experimental conditions. The mass distribution constant of solute between the surface of the carrier gas bubbles and aqueous phase of the process can also be evaluated. Introduction Sublation as a separation technique based on the adsorptive bubble (adsubble)processes, is a collection process opposite to precipitation, in which surface-active solutes, or solutes made surface active with a suitable surfactant, are separated from water. Solvent sublation is an option to ion-flotation, where the sublate formed between solute (colligend) and an oppositely charged surface active agent (collector) is adsorbed on the bubble surfaces of an ascending gas stream and collected into an immiscible organic solvent layer placed on top of the water column [1][2][3][4][5]. This technique can be recognized as an alternative to normal, equilibrium solvent extraction and viewed as a non-equilibrium transport extraction. In transport extraction, the transfer of the hydrophobized solutes from a stagnant bulk aqueous phase into the stationary organic phase takes place only at the relatively small interface of the phases, where true equilibrium distribution of the solute between phases is only established [4,5]. Therefore, in the separation of solutes from relatively large volumes of water (i.e., with high preconcentration factor), the kinetics of the transport extraction may play a considerable role in the separation performance, e.g., in comparison with conventional solvent extraction, where the separation of solute takes place in the bulk aqueous phase through immeasurable large contact surface area of the phases during their intensive mixing.The aim of this paper was to investigate the kinetics of the transport extraction under static conditions from a stagnant aqueous phase into a stationary organic phase (benzene), using a 13112-N-cetylpyridinium chloride (CPC) cationic surfactant complex pair model system [6,7]. Both liquid-liquid transport extraction and polyurethane foam (PU) supported transport extraction were applied. Relevant kinetic equations have been derived, from which the separation efficiency, the mass-transfer rate constant and the separation half-time of the process can be calculated in dependence

The removal of humic acids from water by solvent sublation

“…Recently both the mechanism and kinetics of solvent sublation were investigated by Palagyi et al [21,22]. They have proposed an ionic associate formation mechanism and second-order kinetics in the separation of iodide from water by solvent sublation with CPC (N -cetylpyridinium chloride) into benzene.…”

Studies on the mechanism of Indigo Carmine removal by solvent sublation

“…Recently Palagyi [17,18] has proposed an ionic associate formation mechanism and second order kinetics in the separation of iodide from water by solvent sublation with CPC (N -cetylpyridinium chloride) into benzene. However, studies of both the kinetics and thermodynamics of the solvent sublation are few [19][20][21].…”

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