Determination of recovered Cadmium and Nickel from spent alkaline batteries using acidic solutions and AAS measurements

This research include the recovery study of cadmium and nickel from spent alkaline batteries was conducted by two different acidic solutions. The first one is nitric acid, which was used for cadmium recovery; the other is sulfuric acid, which was used for nickel recovery. Many factors affected the recovery process were studied, such as concentration, volume, time, weight and temperature. The parameters which effect on the precipitation of metal ion from leaching solution were also studied, such as pH, time, concentration and temperature. The recovery percentages of metal ion were found to be 98.5% of cadmium using optimum conditions (5 M HNO3, 2 gm sample, 2 hr, and 20 ml acid volume) and 99% for nickel using (5 M H2SO4, 2 gm sample, 2 hr, and 20 ml acid volume). The precipitation processes were carried out using (2 M NaOH) solution. The precipitation percentages were found to be 98.6% and 99.1% of cadmium and nickel respectively. The purification processes were conducted using double distilled water. The purity of products Cd (OH)2 and Ni (OH)2 was found to be 98.08% and 98.23% respectively. The concentration of metal ion in the solutions was measured using AAS; the method was linear with R of (0.9995 and 0.9993) for Ni and Cd respectively.


Introduction
Cadmium -Nickel power supplies account for about 10% of all chemical current sources in use [1].Various conventional methods for the disposal of the spent batteries which were used in the recent past involve methods such as disposition, stabilization and recycling processes.[2].Recycling that constitutes the most generally acceptable environmentally friendly method of managing these wastes must be taken seriously, to minimize resources or on virgin materials for productions in the industry as well as for the sustainability of the natural resources [3].Any recycling technology that is developed should therefore be designed so as to fully recover these metals in the finished product, thus preventing the formation of gaseous emissions and keeping these metals out of waste water [4].Hydrometallurgical routes are commonly found more economical and efficient than pyrometallurgical ones.Hydrometallurgy has the advantage of working at low temperature for use of aqueous solutions generates little waste gas.The hydrometallurgical technologies that can be used for recycling mainly entail converting metals to a solution by basic or acid leaching.The metals can be recovered from the solution by precipitation, electrolysis, or liquid extraction [5 -9].In recent years, numerous studies on the treatment, recycling and determination of metals in batteries by hydrometallurgical processes and AAS mesurements have been performed [10 -22].In the present study a hydrometallurgical method for cadmium and nickel recovery from spending batteries was developed using an acidic medium for leaching process and basic medium for precipitation of recovered metals from leaching solutions as metal hydroxide.The obtained precipitates were purified using an aqueous solution.The more dilution solutions were preparation by dilution law.

-Recovery of electrode materials:
The components of spent alkaline batteries were separated manually.An anode (negative electrode) which contains cadmium was leaching with nitric acid, while the cathode (positive electrode) which contains nickel (Table 1, illustrate the chemical analysis of electrode powder ) was leaching using sulfuric acid.The leach solutions which contain (cadmium and iron) or (nickel and iron) were filtered and diluted.After dilution the pH of the solutions was adjusting up to 3 to remove iron from mother liquor solutions.The leach solutions which are iron free and contain cadmium or nickel were further used for the precipitation of Cd and Ni as hydroxide at pH 10.5 and 11 respectively, using 2 M sodium hydroxide solution.The hydroxides of metals were purified with double distilled water to remove sodium nitrate and sodium sulfate from precipitates.M were used for the recovery of Cd and Ni respectively (table 4 and figure 3).The obtained results indicate that the recovery percentages were increased as the concentration of solutions of acid was increased until reaching 5 M, after that the value of increasing being small or near constant value.This study was carried out using different volumes of acid (5, 10, 15, 20, 25 ml) which have a concentration of 5M.The results obtained are tabulated in table 5, which revealed that the recovery percentages were increased as the volume of solutions of acid was increased until reaching 20 ml, after that the value of increasing being small or near constant value as shown in figure 4.  6 and figure 5).The obtained results indicate that the recovery percentages were increased at the time of leaching was increased until reaching 120 min., after that the value of increasing being small.In this study the effect of leaching temperature on recovery of Cd and Ni was investigated.

Table. 5: the obtained results from solution volume study.
The solutions of nitric acid and sulfuric acid have a concentration of 5 M were used for the recovery of Cd and Ni respectively, at different temperatures (table 8 and figure 6).The obtained results indicate that the recovery percentages were increased as the temperature of leaching was increased until reaching 70 o C, after that the value of increasing being small or decreased due to the re-precipitation process which occurs at high temperature.11 and figure 9).The obtained results indicate that the precipitation percentages were increased as the time of precipitation was increased until reached 120 min., after that the value of increasing being small or near constant.12 and figure 10).The obtained results indicate that the precipitation percentages were increased as the temperature of precipitation was increased until reaching 25 o C, after that the value of increasing being small or decreased due to the re -solvation process which occurs at high temperature.
Table .12: the obtained results from temperature study.These studies were carried out using double distilled water to remove impurities such as sodium sulfate from nickel precipitate and sodium nitrate from cadmium precipitate.Many parameters affected the purification process such as (time, temperature and number of washing process) were studied.The results obtain are tabulated in table 13.The purity of products Cd (OH)2 and Ni (OH)2 was found to be 98.08% and 98.23% respectively.

ForTable. 2 :P 1 -Table. 3 : 1 . 2 -
determining the linearity, a series of solutions have a different metal ions concentration range of (1, 2, 3, 4, 5, 6, 8, 10, 12 and 15 ppm) were prepared by simple dilution of stock solutions.The absorbance of these solutions was measured at (228.8 and 236.0) nm for Cd and Ni respectively.The calibration curves were obtained by plotting absorbance versus known Vol: 13 No:2 , April 2017 DOI: http://dx.doi.org/10.24237/djps.1302.216CP-ISSN: 2222-8373 E-ISSN: 2518-9255 concentrations in ppm. Figure 1, illustrate the calibration graph Ni and Cd by Atomic absorption spectroscopy (AAS).The method were linear with an R 2 of (0.9995 and 0.9993) for Ni (II) and Cd (II) respectively.Linearity was determined by the regression analysis.The obtained results were tabulated in Table 2, shows that the value of tcal is larger than ttab value, and R 2 values are(0.9995and 0.9993), which indicating that there is a strong correlation between the variation of concentration and response.Summary of linear regression for the variation of absorbance with metal ions concentration using first degree equation of known form y = b[X] + a. No:2 , April 2017 DOI: http://dx.doi.org/10.24237/djps.1302.216CStudy of the leaching solution type: In this set of experiments the investigation of the leaching solution type was studied.Different types of solutions were used to carry out this study.The solutions have a concentration of 2 M (H2SO4، HNO3، HCl ،NaOH، NaHCO3, KOH، Na2CO3) was used for recovery of metal ion as shown in Table 3 and Figure 2. The results obtained revealed that the highest recovery values were occurring with the acidic solution, while the lowest values occurred with the basic solution.The highest recovery percentage of cadmium was found to be 61.2% of nitric acid solution, while the highest recovery percentage of nickel was 92.56% of sulfuric acid solution.The recovery percentage was calculated as follows: Recovery percentage of Nickel and Cadmium for several type of solution.No:2 , April 2017 DOI: http://dx.doi.org/10.24237/djps.1302.216CP-ISSN: 2222-8373 E-ISSN: 2518-9255 Effect of leaching solution concentration: In this study the effect of solution concentration on recovery of Cd and Ni was investigated.Different solutions of nitric acid and sulfuric acid have a concentration of(1,2,3,4,5,6)

1 -
Effect of pH on precipitation:In this set of experiments the precipitation of Ni and Cd from free iron leaching solution was investigated.A solution has concentration 2 M NaOH was used for selective precipitation of iron ion at different pH (Table10).The results obtained indicated that the precipitation percentages of Ni and Cadmium from leaching solutions were reached its highest precipitation values at pH 11 and 10.5 respectively.The lose percentages values of the metals were decreased as value of solution pH was increased, as shown in figure8.

Vol: 13
No:2 , April 2017 DOI: http://dx.doi.org/10.24237/djps.1302.216CP-ISSN: 2222-8373 E-ISSN: 2518-9255 2.2.2 -Effect of precipitation time: In this study the effect of precipitation time on the precipitating process of Cd and Ni was investigated.A solution of sodium hydroxide has a concentration of 2 M was used for the precipitation of Cd and Ni at different time (Table Fig: 8: relationship between pH Vs. % metals precipitate or lose