Evaluation of Recovering Nickel Ions by Supported Liquid Membrane with Strip Dispersion
Date Issued
2010
Date
2010
Author(s)
Lin, Ko-Chih
Abstract
In terms of the residual wastewater contains no fully reacted nickel ions in electroless nickel process, recover the valuable nickel ions could not only reduce environmental pollution but also reuse them in electroless nickel process. The main purpose of this research is to develop a technique that could be used to recover nickel ions from an aqueous solution and concentrates them to be reusable in electroless nickel process. The feed solution contains 1000-3000 mg/L nickel ions (1000 mg/L, mainly) simulated electroless nickel wastewater of anions (sulfate).
In this process, we chose D2EHPA as extractant with diluent Isopar-L. At first, we recovered nickel ions by supported liquid membrane with strip dispersion (SLMSD). The feed solution pH value was 6. Once the process proceeded, the feed solution pH suddenly decreased to 2-3. By using 0.6 M D2EHPA extractant, the concentration of nickel ions could only be decreased from 1000 mg/L to about 700 mg/L in four hours operation. In the first 50 minutes the process could extract 200 mg/L nickel ions, after 50 minutes the extraction rate was much slower. We observed feed solution pH value decrease to calculate how the hydrogen ion exchange to aqueous solution and found out the reason why feed solution pH value decreased drastically was that the small volume hydrogen ions could let the feed solution pH value decreases drastically. We realized that the whole system is very sensitive to the pH value. We used sodium carbonate to increase the feed pH, the feed solution of nickel ions 1000 mg/L completely extracted to the organic phase. 3000 mg/L of nickel ions could also be effect for the complete extraction.
We used the supported liquid membrane with strip dispersion to recover nickel ions and 5M H2SO4 aqueous solution as a strip. We expected to get highly concentrated nickel ions by using sulfuric acid, but we found that even though we could fully extract nickel ions via adding base into 1000mg/L concentration nickel ions feed solution to increase pH in the process, we could not meet stripping phase to 5 fold concentration (Actually, 3 fold or so). We conjectured the reasons that broke nickel ions concentration conservation were difficult to stripping and water transfer effect. We improved the efficiency by lower sulfuric acid concentration and results in higher recovery. Finally, we could approach nickel ions concentration to 5 fold.
Subjects
Nickel
Electroless nickel
D2EHPA
SLMSD
Sodium carbonate
water transfer
SDGs
Type
thesis
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