Abstract
New technologies for iodine separation and recovery are required to decrease environmental pollution and improve iodine production. Separation and recovery of iodine (I2) in aqueous solution was achieved using permeation and chemical desorption (PCD) with a silicone rubber membrane (SRM). The SRM separated an aqueous feed solution from an alkaline or reducing recovery solution such as a mixture of sodium hydrate and sodium sulfate. The I2 crossed the membrane from the aqueous feed solution into the recovery solution, where it was converted into iodide (I–). Iodide in the recovery solution did not return to the feed solution across the SRM. An acidic feed solution promoted a high recovery of iodine. The permeation process followed first-order kinetics, allowing the overall mass-transfer coefficient and parameters related to permeation of I2 through the SRM to be determined. Permeability of I2 increased with temperature, and the apparent activation energy (Ea) for penetration of I2 through the SRM was determined. The value of Ea for I2 was of the same order of magnitude as those for phenols and anilines. The large membrane/aqueous distribution coefficient for I2 indicated that I2 had a high affinity toward the SRM. These results indicate that the PCD method is effective and powerful for separation and recovery of iodine from aqueous solutions.
Highlights
Iodine is used in many applications, such as X-ray contrast media [1] and disinfectants [2], because of its high reactivity
The I2 crossed the membrane from the aqueous feed solution into the recovery solution, where it was converted into iodide (I–)
These results indicate that the permeation and chemical desorption (PCD) method is effective and powerful for separation and recovery of iodine from aqueous solutions
Summary
Iodine is used in many applications, such as X-ray contrast media [1] and disinfectants [2], because of its high reactivity. Potassium iodide, which is essential to growth, is often added to table salt and feed to prevent iodine deficiency. Iodine and iodine compounds are used as photo-sensitizers, catalysts, stabilizers, polarizing films on liquid crystal displays, and reaction intermediates [3]. Iodine in brine is usually produced through a blowing-out process [3,4,5]. The iodine concentration in brine is 60 - 350 mg·L–1 (0.2 - 1.3 mM) [6], but the recovery of iodine from brine requires large-scale equipment. The development of new small-scale, energy-saving processes for iodine separation and recovery need to be developed to decrease environmental pollution and improve iodine production
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