Norman N. Li

Extraction of Copper by Liquid Membranes

Abstract Important variables governing the permeation of copper ion through liquid membranes and their effects on the separation process are described. These variables are membrane viscosity, treatment ratio (volume ratio of emulsion to feed in mixer), complexing agent concentration, internal droplet size, internal phase leakage, and copper concentration in the internal phase. The information is needed for scaling-up of equipment and further process development. The economic evaluation based on bench-scale pilot plant runs shows this process is 40% cheaper than solvent extraction.

Extraction of Uranium from Wet Process Phosphoric Acid by Liquid Membranes

Abstract The liquid membrane process can effectively separate and concentrate uranium from wet process phosphoric acid and is economically superior to solvent extraction systems. The paper describes the process, compares it to other extraction schemes, and shows how it can be used for uranium recovery. A mathematical model useful for design purposes is presented and the effect of important variables is discussed.

Extraction of phenolic compounds and organic acids by liquid membranes

Abstract Liquid membrane emulsions were used to extract phenolic compounds and organic acids from their aqueous solutions. The emulsions contained caustic as the reactive agent. When the phenolic compounds and organic acids permeated through the liquid membranes into the emulsion droplets, they reacted with caustic and became ionized. The ionized species could not permeate through the liquid membranes and therefore were held in the emulsion droplets. The conclusions of this recent investigation are: (1) More than 99% of phenol and cresols can be extracted in less than 1 minute. (2) Acetic and propionic acids can also be extracted but at much slower rates. However, if the amount of caustic is not sufficient to react with all the permeating compounds, the acids will be extracted preferentially to the phenols. (3) The acids can only be extracted at low pH (acidic) whereas the phenolic compounds can be extracted at pH of 7. (4) The extraction rates for phenol and acetic acid are the same in individual-compound and binary-mixture permeations. (5) The extraction can be described by a mass transfer model.

Facilitated Transport Through Liquid Membranes

Abstract Liquid membranes, developed by Li,1 offer a new and effective means for separation of mixtures. In order to maximize the utility of this concept, it is necessary to maximize the concentration gradient of the diffusion, species across the membrane.

Membrane Recovery in Liquid Membrane Separation Processes

Abstract The use of conventional electrostatic coalescers with bare metal electrodes for the separation of rich water-in-oil emulsions often causes the formation of a sponge-like emulsion. This effect was eliminated by the use of insulated electrodes in a coalescer that allow the application of high electric fields at the oil/water interface, resulting in a clean separation of oil from water.

Extraction of chromium and zinc from cooling tower blowdown by liquid membranes

Abstract Since the invention of liquid membrane technology in 1968, a number of potential applications have been investigated at Exxon Research and Engineering Company. This paper reviews the recovery of metal ions from an aqueous solution, with specific details of research on the simultaneous extraction of chromium(VI), chromium(III), and zinc from a cooling tower blowdown stream. The important factors affecting the extraction of chromium and zinc are discussed.

Separations of organic compounds by liquid membrane processes

By allowing a hydrocarbon mixture to permeate through a thin film of a liquid with which it is essentially immiscible, separation of the constituents of this mixture may occur. The phenomenon has been observed with both unsupported and supported liquid films. This paper discusses liquid membrane permeation (LMP) through unsupported liquid films, especially those present when an emulsion of two liquids is dispersed in the form of relatively coarse drops in a third liquid into which permeation is allowed to occur from within the drops. The mechanism underlying the separation phenomenon, differential permeation rates, can be used to formulate an actual separation process. Rate equations can be derived which allow sizing of equipment and comparison of LMP with other separation techniques. Possible improvements involving preferential complexing agents in the membrane phase, as well as potential applications to oil refining and other chemical processes, are discussed.