Acta Chim. Slov. 2004, 51, 793-798. 793 Technical Paper ELECTROLYTIC RECOVERY OF NICKEL FROM INDUSTRIAL HYDROGENATED VEGETABLE OIL (GHEE) WASTE Sirajuddin,a* Lutfullah Kakakhel,b Ghosia Lutfullah,c and Rafi Ullah Marwatd a National Center of Excellence in Analytical Chemistry, University of Sindh, Jamshoro, Sindh, Pakistan * National Center of Excellence in Physical Chemistry University of Peshawar, NWFP, Pakistan c Center of Biotechnology, University of Peshawar, NWFP, Pakistan d Government Degree College, Laki Marvvat, NWFP, Pakistan Received 25-05-2004 Abstract Solid waste of hydrogenated vegetable oil locally called ghee waste obtained from Bara Ghee Mills (pvt.) Ltd. Khyber Agency (tribal area) NWFP has been first de-oiled and then digested with 20% sulphuric acid in order to get the nickel dissolved into aqueous medium for electrolytic recovery. A 65% nickel with metallic, magnetic and shining properties has been recovered at a celi potential of 3.7 V, pH, 3.8, and addition of 3.2 ml of 6M NH3 using stainless steel static sheet electrodes as a result of just 15 minutes electrolytic deposition. Key words: ghee waste, stanless steel electrodes, electrolytic nickel recovery. Introduction Several workers1"3 have electrolytically removed or recovered heavy metals such as Cr, Ni, Cd, Cu, Zn, Ag, Au, Co, Pb, Sn, Fe, etc. from different types of samples. Vergonova and Genkin4 have investigated and recommended the use of Ti electrodes together with steel electrodes for the removal of Ni, Zn and Cu from waste water containing these metals. A review with 29 references has been presented by Bergmann and Lourtchouk5 to discuss the removal of nickel from processing solution as a standard requirement in operating electroplating baths. The present work is concerned with the rapid recovery of metallic nickel using different types of static sheet electrode couples in a simple celi at different parameters in a short period of electrolysis. Experimental Preparation of solutions Standard solutions were prepared from analytical (Merck) grade salts of respective material. Distilled water was used for final washings and preparation of ali solutions. Sirajuddin, L. Kakakhel, G. Lutfullah, R. U. Manvat: Electrolytic Recovery of Nickel From Industrial... 794 Acta Chim. Slov. 2004, 51, 793-798. Oil extraction by sohxlet extractor6 A weighed quantity of well chopped and thoroughly mixed solid waste of hydrogenated vegetable oil (ghee waste) collected from Bara Ghee Mills (Pvt) Ltd. was placed in a thimble of filter paper kept inside the extraction chamber of Sohxlet extractor. A reflux condenser was fitted to the upper end while a one liter volumetric flask containing sufficient petroleum ether and acetone in 50% v/v ratio as solvent mixture to the lower end of the chamber. The whole assembly was vertically set in an electrothermally controlled mantle and heated to boiling at controlled temperature. After 10-20 cycles, the oil extracted from the sample was collected in the recovery flask which was separated from solvent mixture by simple distillation method. The de-oiled sample was first dried at room temperature and then in an oven at 110 °C for 10-15 minutes. It was then cooled in a desiccator and reweighed. Nickel determination The de-oiled sample (1 g) from above treatment was digested with 20% H2S04 solution for about one hour according to the same procedure as described for HN03 digestion.9 The final volume was adjusted to lOOOml mark with distilled water. Nickel was analyzed by three methods, i.e. volumetrically,7 photometrically8 and voltammetrically.9 The actual weight (average of three weights) was 724 ppm nickel. This solution was used as a stock standard for preparing dilute solutions of nickel ions whenever required. On a percentage basis the weight of different contents were; oil, 43.95%; nickel 40.60% and other solids 15.45%. Electrolytic recoveij of nickel10 100 mL of 200 ppm nickel ions containing solution having sufficient amount of 20% H2S04 and 6M NH3 was taken in electrolytic celi. The celi may contain different types of static sheet metallic electrode couples used for electro-winning. The stirring bar was put inside the celi already placed on a hotplate adjusted at 300 revolutions per minute (RPM). Pre-weighed electrodes (anode and cathode) were fixed in a holder at a 3 cm distance from one another and hung in the solution at fixed depth. The electrodes were then connected to a power supply. The electrolytic deposition of nickel was started by starting the power supply and stirring of solution at once. Sirajuddin, L. Kakakhel, G. Lutfullah, R. U. Manvat: Electrolytic Recovery of Nickel From Industrial... Acta Chim. Slov. 2004, 51, 793-798. 795 As soon as the electrolysis was over, the current flow and stirring were stopped. The electrodes were taken out of the celi, detached from wires and holder and dried in an oven at 110 °C for 10 minutes. The electrodes were then cooled to room temperature in a desiccator and reweighed. The difference in two weights gave the quantity of deposited nickel. The mean of three replicate runs gave the actual value. Results and discussion The recoverv of nickel on steel cathode and anodic deposition of nickel oxide (NiO) at different celi potentials using 6M NH3 and 20% sulphuric acid for pH adjustment and as mixed electrolvtic medium at some constant parameters like, pH, 7.0, volume of each electrode, 1.8×5.7×0.03 cm3, deposition tirne, 15 min and room temperature, 30 ±1 °C (mostly same for other figures) are evident from Figure 1. 60 50 ^ 40 30 -20 -10 0 -*-% cathodic Ni recovery| -A— % anodic NiO recoverv 1.5 2 2.5 3 Cell potential (V ) 70 -j 60 50 -40 -30 -20 10 -i 0 23456789 pH Figure 1. Effect of cell potential on cathodic Ni/ Figure 2. Cathodic Ni recovery/ dissolution of steel anodic NiO recovery using steel electrodes couple. anode at different pH values. The best recovery of 51.5% nickel with a standard deviation value of ±0.9 occurs at an optimum potential of 3.7 V with no deposition of NiO which is quite comparable with the value of 3.0 V, as described by Veraraghavan and Dambal12 for best Ni recovery using steel electrodes couple. Figure 2 shows the cathodic nickel recovery and dissolution of steel anode at different pH values at a potential of 3.7 V. The results teli that a maximum recovery of 64% is obtained at a pH value of 3.8 and a constant celi potential of 3.7 V with least value of ±0.1 standard deviation. The pH value of 3.8 is in good accordance with the pH ranges of 3-6 and 2-3 as mentioned in ref 5 and ref 12 respectively for maximum Ni recovery. Sirajuddin, L. Kakakhel, G. Lutfullah, R. U. Manvat: Electrolytic Recovery of Nickel From Industrial... 796 Acta Chim. Slov. 2004, 51, 793-798. A 0.6 mg dissolution of anode also takes place at this pH, however, this value is less than other dissolution values. Figure 3 describes the cathodic nickel recovery and anodic dissolution at different volumes of 6M NH3 addition at optimized pH and potential values of 3.8 and 3.7 V respectively using steel electrodes. The highest recovery of 66.5% nickel takes place at 3.1 ml addition of 6M NH3 with 0.5 mg dissolution of anodic steel. To avoid the danger of anodic dissolution/ NiO deposition, 3.2 ml of 6M NH3 was selected as optimum value which gives a 65% nickel recovery. /0 -, 60 - 50 - 40 - 30 - 20 - 10 - 0 - -¦— % cathodic Ni recovery -A— Anodic dissolution A A A A—A A A 23 45 67 Volume of NH3 (ml) 60 50 40 -30 -20 10 0 ¦ % cathodic Ni recoverv -% anodic NiO recovervl 2 2.5 3 3.5 Cell potential ( V ) 4.5 Figure 3. Dependence of cathodic Ni recovery / Figure 4. Effect of cell potential on cathodic Ni/ anodic dissolution on different volumes of NH3 anodic NiO recovery using steel anode with copper added. cathode. The results also show a minimum standard deviation value of ±0.1 as compared to other values. The literature lacks such studies, in čase of nickel; however, these values may be betterly described in the light of results reported by Jerzy et al.11 who studied the effect of amount of ammonium hydroxide on silver recovery. Another example is the use of 0.2-0.3% NaCN solution in čase of gold recovery.13 The use of copper cathode and steel anode couple electrodes has also been studied for the nickel recovery and NiO deposition at different celi potentials and pH, 7.0 with the remaining conditions same as for steel electrodes (see Figure 4). The results teli that 44.0% nickel is recovered in just 15 minutes of electrolysis with a standard deviation of ±0.8 at a celi potential of 3.2 V, as compared with 100% Ni recovery in 10 hours electrolysis on steel electrodes as reported.12 The electrolytic recovery of cathodic Ni and anodic NiO using steel anode and copper cathode couple was also studied at different pH values. Fortunately, the optimum Sirajuddin, L. Kakakhel, G. Lutfullah, R. U. Manvat: Electrolytic Recovery of Nickel From Industrial... Acta Chim. Slov. 2004, 51, 793-798. 797 pH value obtained was also 7.0 with a maximum value of 44.0% cathodic Ni recovery. So the values are not indicated to simplify the study and avoid repetition of data. This pH value is close to the pH range of 3-6 described in5 but quite different from pH range of 2-3, as cited earlier12 for maximum nickel recovery. Our value of pH, 7 is however, advantageous by providing a neutral medium, which is helpful to minimize anodic dissolution. Furthermore, the NiO deposition in such studies protects anodic steel against dissolution, but its significant value can create concentration polarization thus decreasing the rate of cathodic nickel recovery. Acknowledgements We do highly acknowledge the authorities of Bara Ghee Mills (pvt.) Ltd, Bara, Khyber Agency, NWFP for providing us the sample of hydrogenated vegetable oil (ghee) waste. We also appreciate the Director and Staff members of National Center of Excellence in Physical Chemistry University of Peshawar, NWFP, for giving us ali facilities required to complete this study. Conclusion The overall results show that nickel recovery in case of using steel electrodes is superior to that of using copper cathode and steel anode due to best magnetic properties, metallic nature, greater recovery (65% as compared to 44.5%) and easily scratchable deposit. References 1. S. Horold, Galvanotechnik 1983, 73(6), 589-593. 2. G. Diaz, C Frais, J. Palma, Global Symp. Recycl. Waste Treatment Clean. Technol., Proč, Madrid, Spain 1999, 1, 681-690. 3. A. G. Tyson /* Heavy Met. Environ. Int.Conf. Edinbourgh, UK 1983, 2, 988-991. 4. R. V. Vergunova, V. E. Genkin, Chem. Abstract 1991, 114, 253405b. 5. H. Bergmann, T. Lourtchouk, Galvanotechnik 2000, 91(6), 1710-1715. 6. A. E. Greenberg, R. R. Trussell, L. S. Clesceri, Standard Methods for Examinations ofJVater and JVaste Waterl9%5. 7. A. I. Vogel, Text Book of Quantitative Inorganic Analysis Including Elementary Industrial Analysis John Willy and Sons, Inc. New York, London, Sydney, Toronto, 1978, pp 630. 8. A. Mumtaz, Determination of Nickel in Ghee Samples, M. Phil Thesis 1994, 45-46, National Center of Excellence in Physical Chemistry, Peshawar, Pakistan. 9. T. R. Peter, S. J. Melinda, W. G. Gordon, Electroanalysis 1989, 1(6), 541-547. 10. K. Lutfullah, Sirajuddin, L. Ghosia, A. Hamid, M. Rafiullah, and H. Arshad, Pak. J. Phys. Chem. 2003, 14, 37-44. Sirajuddin, L. Kakakhel, G. Lutfullah, R. U. Manvat: Electrolytic Recovery of Nickel From Industrial... 798 Acta Chim. Slov. 2004, 51, 793-798. 11. S. Jerzy, H. Irena, D. Wladyslaw, Arch. Metali. 1989, 34(2), 217-237. 12. R. Veeraraghavan, R. D. Dambal, J. Electrochem. Soc. India 1982, 31(2), 27-32. 13. Pakistan-Gold Exploration and Mineral Analysis Project, Metallurgical Testing Procedure Manual, Volume II. MT Leyshon Gold Mine Ltd., Pageless attachment No. 6, 1988. Povzetek Podan je postopek za izolacijo niklja iz odpadka po pridobivanju olja iz rastlinskega materiala. Razoljen odpadek se izlužuje z 20%-no žveplovo (VI) kislino, dobljeno nikljevo lužnico uravna na pH 3,8 z dodatkom 6 M raztopine amoniaka ter elektrolizira z elektrodami iz nerjavnega jekla pri 3,7 V. Dobitek niklja je že po 15 minutah elektrolize 65%, produkt pa je lahko odstranljiv nikelj s kovinskim leskom in dobrimi magnetnimi lastnostmi. Obravnavan je tudi problem odlaganja nikljevega oksida na anodo in raztapljanja le-te. Sirajuddin, L. Kakakhel, G. Lutfullah, R. U. Marwat: Electrolytic Recovery of Nickel From Industrial...