Selective separation of Chromium (III) from electroplating effluents by ion-exchange processes
Advancing the chemical engineering fundamentals
Electrochemical Engineering - I (T2-14a)
Keywords: Ion-exchange; Chromium; Equilibrium; Diphonix
Chromium is a common pollutant found in a variety of industrial effluents as Cr(III) or Cr(VI), including those from metal working industries such as the electroplating. The separation and recovery of the chromium from of these effluents should be assured for environmental protection and economic reasons. Indeed, from the environmental viewpoint, this metal is usually considered very toxic for humans, animals and even plants, being the hexavalent form potentially carcinogenic when inhaled. The World Health Organization has set maximum tolerable limits of 0.05 mg/l for Cr(VI) and 0.17 mg/l for Cr(III) in drinking water. As regards the economic issue, the chromium can be recovered from the treatment of electroplating rinses and wastewater of high concentration in order to be reused in the process and as a result this it is possible to improve the global process economy.
The conventional techniques in use for metal control are based on chemical precipitation coupled to pre- or post-oxidation/reduction and followed by filtration. The main disadvantage of these techniques is the production of solid residues (sludges). Ion-exchange processes have been frequently used as an effective alternative technique for the treatment of industrial effluents containing heavy metals and for the recovery of the valuable components. Various studies have been published reporting the chromium removal using ion-exchange resins.
The present work reviews the application of this technology to treat industrial effluents containing heavy metals and presents results on the uptake of Cr (III) from aqueous solutions using the polyfunctional chelating exchange resin Diphonix. Batch equilibrium experiments were carried out to evaluate the sorption capacity of the resin. The effects of temperature and pH on the adsorption equilibrium were studied. Moreover, saturation and regeneration experiments in column were also performed in order to study the dynamic behaviour of the process. The chromium solutions employed in these experiments were industrial effluent samples and synthetic solutions.
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Presented Tuesday 18, 11:20 to 11:40, in session Electrochemical Engineering - I (T2-14a).
