Paper Title
Non-Toxic Organic Diluents for Nickel (II) Extraction from Aqueous Solution: Optimization by Response Surface Methodology (RSM)

In order to promote a friendly environment for separation processes, the application of non-toxic diluents to nickel (II) extraction was investigated. Sunflower oil, soybean oil and rice bran oil were used as the diluents. Each non-toxic diluent was mixed with an extractant viz. Di-(2-Ethylhexyl) Phosphoric Acid (D2EHPA). Their utilization was operated by a Liquid-Liquid Extraction (LLE) system. The optimum conditions for the influencing parameters such as pH of aqueous solution and nickel (II) concentration were examined using Response Surface Methodology (RSM) based on Face-Central Composite Design (FCCD). Under optimum conditions as determined, the toxic diluent of kerosene was employed in the nickel (II) extraction system. Thereafter, the extraction efficiency of non-toxic diluents was compared with that of the toxic one. Results showed that the diluent of rice barn oil provided maximum percentage of nickel (II) extraction at 90.33 % under optimum conditions: namely, aqueous pH 4.64 and 5 ppm of nickel (II) concentration. Comparative results indicated that all the non-toxic diluents provided higher extraction percentages than that of the toxic diluent. Keywords - Nickel (II), Non-toxic Diluents, Response Surface Methodology, Liquid-Liquid Extraction.