Academia.eduAcademia.edu

Figure 6 – uploaded by souad djerad

See full PDFdownloadDownload figure
clear difference is observed between the results obtained with the three leachants. This is probably related to the nature of the anion of each acid.

Figure 6 clear difference is observed between the results obtained with the three leachants. This is probably related to the nature of the anion of each acid.

Related Figures (10)

in the form of nickel sulfate by leaching with sulfuric acid under the following conditions (sulfuric acid concentration of 80%, 50 min of reaction and 70°C). Al-Mansi and Abdel Monem [17] recovered 99% of nickel from Egyptian spent catalysts under the following experimental parameters (50% sulfuric acid concentration, a solid- to-liquid ratio of 1:12 g/g and a contact time over 5 h). Abdel-Aal and Rashad [14] recovered 94% of nickel after leaching spent nickel oxide catalysts with sulfuric acid under the conditions (-200 + 270 mesh spent particle size, 85°C, 150 min, sulfuric acid concentration of 50% and solid/liquid ratio of 1:20 g/mL).
in the form of nickel sulfate by leaching with sulfuric acid under the following conditions (sulfuric acid concentration of 80%, 50 min of reaction and 70°C). Al-Mansi and Abdel Monem [17] recovered 99% of nickel from Egyptian spent catalysts under the following experimental parameters (50% sulfuric acid concentration, a solid- to-liquid ratio of 1:12 g/g and a contact time over 5 h). Abdel-Aal and Rashad [14] recovered 94% of nickel after leaching spent nickel oxide catalysts with sulfuric acid under the conditions (-200 + 270 mesh spent particle size, 85°C, 150 min, sulfuric acid concentration of 50% and solid/liquid ratio of 1:20 g/mL).
Kinetic data for pure minerals are important as the data may then be used to evaluate leaching of more complex systems containing several mineral constituents such as in ores or spent catalysts. The work described in this paper is an attempt to optimize a leaching process to recover nickel from NiO/a-Al2Os fresh catalyst by testing 5 reagents under the same conditions: three inorganic acids (HCl, HNOs and HSQ.) and two alkaline solutions ((NHa)2CO3 and CH3COONHsg). To the best of our knowledge, no comparative studies were found dealing with the leaching of nickel oxide with the selected solutions. The aim was to address the factors governing the leaching process and to determine the most efficient and/or an alternative leachant for this system. Fig. 2 - Effect of liquid/solid ratio on nickel dissolution with the three acids after 30 min of reaction.
Kinetic data for pure minerals are important as the data may then be used to evaluate leaching of more complex systems containing several mineral constituents such as in ores or spent catalysts. The work described in this paper is an attempt to optimize a leaching process to recover nickel from NiO/a-Al2Os fresh catalyst by testing 5 reagents under the same conditions: three inorganic acids (HCl, HNOs and HSQ.) and two alkaline solutions ((NHa)2CO3 and CH3COONHsg). To the best of our knowledge, no comparative studies were found dealing with the leaching of nickel oxide with the selected solutions. The aim was to address the factors governing the leaching process and to determine the most efficient and/or an alternative leachant for this system. Fig. 2 - Effect of liquid/solid ratio on nickel dissolution with the three acids after 30 min of reaction.
The process conditions studied included the nature of the leachants, their concentration, liquid/solid ratio, stirring speed, temperature, mixture of acids, the addition of anions and time.
The process conditions studied included the nature of the leachants, their concentration, liquid/solid ratio, stirring speed, temperature, mixture of acids, the addition of anions and time.
needed to reach high dissolution efficiency was decreased with increasing temperature. In the case of HCI, the dissolution efficiency increased from 58.6% at 50°C to 100% at 80°C after 30 min of reaction. With HNO3 and H2SOu, 8.27% and 7.92% of NiO were dissolved, respectively, at 50°C after 30 min of reaction and increased up to 77.15% and 46.12%, respectively, after the same period of time at 80°C. Even after prolonging reaction time, nitric and sulfuric acids did not reach the dissolution efficiency of HCl since 77.3% with HNOs and 72.8% with H2SOs were registered as maximum at 80°C after 180 min of reaction. Fig. 4 - Effect of temperature on nickel dissolution with the three acids.
needed to reach high dissolution efficiency was decreased with increasing temperature. In the case of HCI, the dissolution efficiency increased from 58.6% at 50°C to 100% at 80°C after 30 min of reaction. With HNO3 and H2SOu, 8.27% and 7.92% of NiO were dissolved, respectively, at 50°C after 30 min of reaction and increased up to 77.15% and 46.12%, respectively, after the same period of time at 80°C. Even after prolonging reaction time, nitric and sulfuric acids did not reach the dissolution efficiency of HCl since 77.3% with HNOs and 72.8% with H2SOs were registered as maximum at 80°C after 180 min of reaction. Fig. 4 - Effect of temperature on nickel dissolution with the three acids.
fig.5 - Effect of the mixture of acids at 2M (a) and 4M (b) on nickel dissolution.
fig.5 - Effect of the mixture of acids at 2M (a) and 4M (b) on nickel dissolution.
concentration of nitric acid may form a passive film that protects metal surface from protons attack while in diluted nitric acid nitrate ion may play the role of corrosion promoter [26]. Our experiments were carried out under concentrated conditions and it seems from the results that the building of passive film was more rapid than the rate of its dissolution. Sulfuric acid was the weakest leachant regardeless of the conditions used. In this case, also sulfate anion seems to be the cause of the weak efficiency of H25O.. It was reported that sulfate ions because they are doubly charged have a strong adsorptive affinity for solid surface hampering consequently its dissolution [27]. Fig. 7 - Effect of ammonium carbonate (a) and ammonium acetate (b) concentration on NiO leaching after 180 min of reaction.
concentration of nitric acid may form a passive film that protects metal surface from protons attack while in diluted nitric acid nitrate ion may play the role of corrosion promoter [26]. Our experiments were carried out under concentrated conditions and it seems from the results that the building of passive film was more rapid than the rate of its dissolution. Sulfuric acid was the weakest leachant regardeless of the conditions used. In this case, also sulfate anion seems to be the cause of the weak efficiency of H25O.. It was reported that sulfate ions because they are doubly charged have a strong adsorptive affinity for solid surface hampering consequently its dissolution [27]. Fig. 7 - Effect of ammonium carbonate (a) and ammonium acetate (b) concentration on NiO leaching after 180 min of reaction.
Fig. 8 - Effect of temperature on NiO leaching with ammoniacal solutions.
Fig. 8 - Effect of temperature on NiO leaching with ammoniacal solutions.
carbonate and acetate under the same conditions (2 M of ammoniacal solution, 350 rpm, 80°C, L/S = 200 mL/g).
carbonate and acetate under the same conditions (2 M of ammoniacal solution, 350 rpm, 80°C, L/S = 200 mL/g).
It is likely that carbonate anion plays a role in this result as with anions in inorganic acids.
It is likely that carbonate anion plays a role in this result as with anions in inorganic acids.
Related topics:
Mineral acids
580 California St., Suite 400
San Francisco, CA, 94104
© 2025 Academia. All rights reserved