An extensive study of Fischer-Tropsch synthesis (FTS) on alumina-supported cobalt catalysts with different amounts of cobalt is reported. Up to 40 wt % of cobalt, is added to the catalysts by impregnation method. The effect of the cobalt loading on the reducibility of the cobalt oxide species, dispersion of the cobalt, average clusters size, water-gas shift (WGS) activity and activity and selectivity of FTS is investigated. Increasing the cobalt loading resulted in increasing the average cobalt cluster size, improvements in the reducibility of Co3O4, decreasing the cobalt surface interaction with the support and decreasing the dispersion of cobalt. The maximum concentration of active surface Coo sites and FTS activity are achieved for the 34 wt% cobalt loading. While the maximum WGS activity is achieved for the 40 wt % cobalt loading. The methane selectivity in the catalyst with 40 wt % of cobalt loading was about 43.7 % less compared to that of the less reducible 8 wt % cobalt catalyst. The C5+ selectivity for the 40 wt % cobalt catalyst was 60.8% higher than that of the 8 wt % Cobalt catalyst.

An approach to recycle precious metals of cathode materials from spent lithium cobalt oxide batteries by using organic citric acid and hydrogen peroxide has been studied in this paper. The effects of molar ratio, solid-liquid ratio, reaction time and temperature on leaching efficiency of cobalt were investigated respectively. Meanwhile the leaching kinetics equation of cobalt was established, and the apparent activation energy of leaching reaction of cobalt was calculated out. The results show that when the molar ratio of citric acid to lithium cobalt oxides is 4:1, solid-to-liquid ratio is 15 g/L, the reaction temperature is 90 oC, the reaction time is 5 h and concentration of H2O2 is 1.0 vol. %, the leaching efficiency could be up to 99.07%. The apparent activation energy of cobalt leaching reaction is 45.724 KJ/mol, and by means of conducting fitting test for the relationship between lithium cobalt oxides powder with different particle sizes and leaching efficiency, it can be concluded that the reaction of lithium cobalt oxides using citric acid and hydrogen peroxide is chemical reaction control.

The aim of this study was to determine the effects of cobalt concentration on cell growth, some biochemical composition, and fatty acids profile of the marine microalga Tetraselmis subcordiformis. Cobalt deprivations did not cause a considerable change in growth photosynthesis activity as compared to the control group. Induction of maximum lipid production was achieved using 0.001 mg L-1 of cobalt-deprived T. subcordiformis. The highest crude protein content (33.75 mg L-1) was observed in 0.001 mg L-1 cobalt. The highest and lowest lipid accumulation in T. subcordiformis was observed in 0.001 mg L-1 and 10 mg L-1 cobalt, respectively. Under cobalt deficient conditions, T. subcordiformis produced a large quantity of saturated fatty acids and iodine and saponification value. Biodiesel characteristics were enhanced with Co+2 reduction. Also, biodiesel quality decreased with increase of cobalt. The results showed that the maximum and minimum carotenoids were observed in 0.1 and 10 mg L-1 cobalt, respectively.

In ruminants, cobalt is essential for synthesis of vitamin B12 by rumen microflora. Emaciation and anemia are the most important consequences of cobalt deficiency in ruminants. This study aimed to investigate the relationship between cobalt, iron, zinc, and manganese levels of soil and forage with each other and with serum levels of cobalt, zinc, and vitamin B12 in emaciated and normal sheep of Ramhormoz city. Eight soil and 8 forage samples were taken from four areas in Ramhormoz city. The soil and forage samples were analyzed. Blood samples were collected from 25 (15 emaciated and 10 normal) and 43 sheep (28 emaciated and 15 normal) from areas with more and less than 0.07 μg cobalt/Kg of DM forage, respectively and were analyzed to determine serum cobalt, zinc, vitamin B12 values and some hematological parameters. The forage cobalt value in Plim (0.052±0.02 mg/kg dry matter (DM)) and Larkiabad (0.054±0.00 mg/kg DM) regions was lower than the standard value. The mean soil iron value (15767±1333 mg/kg arid soil) was more than its critical level in Ramhormoz. The highest soil manganese values in Larkiabad and Plim regions were associated with the lowest forage cobalt values. There was no statistically significant difference between serum levels of cobalt, zinc, and vitamin B12 in the emaciated and normal sheep. It is possible that the high amounts of soil iron and manganese, due to their chelating effects, could reduce the cobalt bio-availability of forage. Contrary to the available literature, the presence of 0.05 μg cobalt/Kg of DM forage is capable of providing sufficient amounts of cobalt and vitamin B12 for sheep in the region.

Removal of cobalt from zinc electrolyte solution is one of the most important and difficult steps in zinc production using hydrometallurgy method. The impact of initial concentrations of cobalt, manganese, and Fe and amounts of potassium permanganate on the efficiency of cobalt removal by potassium permanganate from zinc electrolyte solution was investigated in this research. The results indicated that the higher the initial concentration of cobalt, manganese, and Fe is, the lower the cobalt removal amount will be; however, as the amount of potassium permanganate increases, the efficiency of cobalt removal will enhance. It was also found that, in order to make a permissible level of the dissolved cobalt, the consumption of potassium permanganate should be increased as the concentration of cobalt, Fe, and manganese increases. If the concentration of manganese is more than 500 mg/L, it can impact the reduction of the efficiency of cobalt removal to a great extent; but when the initial concentration of cobalt is high, the significance of the impact of the initial amounts of manganese would decrease. Additionally, if the manganese concentration is less than 200 mg/L, the optimal removal of cobalt (less than 2 ppm) will not occur under any circumstances. The results also indicate that if the potassium permanganate concentration is 1 g/L or lower, the Fe ions in the solution will drastically reduce the cobalt removal efficiency.

In this research, the effects of cysteine on alleviation of heavy metal stress in purple basil plants were studied and some parameters such as fresh weight of shoot and root, chlorophyll a and b content, carotenoids, anthocyanin, and total phenolic compounds and reducing sugar was measured. Research was conducted in two separate trials for the two group pre-treated cysteine and cysteine -cobalt combined treatments. The treatments containing of 0, 500 and 2500 mM cysteine and 0, 100 and 500 mM cobalt was used. Higher concentrations of cobalt decreased photosynthetic pigments, leaf, root and shoot length, fresh weight of roots and shoots while cobalt stress increased, caused reducing sugars, anthocyanins and total phenolics content. Cysteine reduced the fresh weight of roots, reduction sugar, anthocyanins, and total phenolics of plants compared to plant treated with cobalt treatments without cysteine. Thus, this amino acid improved leaf area, root and shoot length, shoot fresh weight and photosynthetic pigments in stress conditions. Generally, the results showed that pre-treatment of cysteine could alleviate low concentrations of cobalt stress effects than higher amounts application of this heavy metal, while combined treatments containing cysteine was more effective at higher concentrations of cobalt.

Conventionally, a film of TiO2 particles of ~300 nm size is employed in DSCs as the back reflector film to enhance the light harvesting. In this study, two electrolytes with different transparencies, iodide-based and cobalt-based electrolytes, were used to investigate the transparency effect of electrolytes on light back-scattering from back scattering layer and also to study its effect on the performance of DSCs. The use of cobalt-based electrolyte is recommended from the view point of optical properties as due to the light absorption in electrolytes, the current density losses are 2.9mA/cm2 and 4.2 mA/cm2 in cobalt- and iodide-based electrolytes, respectively, and the transmission of 100% is observed for cobalt-based electrolyte in 500-600 nm in spite of iodide-based electrolyte. Use of light back-scattering layer, unlike iodide-based cell, causes external quantum efficiency in cobalt-base cell to increase for the wavelengths lower than 350 nm since cobalt-base electrolyte has transparency in this region. In addition, optical calculations demonstrate that in the range 400-500 nm, in which dye has a noticeable absorption, absorption loss is 40% and 30% for iodide- and cobalt-based electrolytes, respectively.

In this research, nanostructured cobalt oxide and nickel cobalt oxide active materials were successfully synthesized by a hydrothermal route. Structural characterizations of the prepared active materials were performed using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and elemental analysis (EDS). The results of these experiments showed that nickel has been successfully doped in the cobalt oxide spinel structure. Also, the microscopic examination showed the nano-rod morphology for the cobalt oxide and nickel cobalt oxide, which yields the high specific surface area for electrochemical reactions, leading to increase energy storage capacitance. Energy storage performance of the prepared active materials was investigated using electrochemical experiments of cyclic voltammetry and galvanostatic charge-discharge in a solution of 6 M KOH in Swagelok standard cell. The specific capacitance of nickel containing cobalt oxide sample (1624 F g-1) was obtained higher than that of cobalt oxide (1020 F g-1) at a current density of 2 A g-1.

In the present study, for the first time, the effect of pyrolysis temperature on the structure of carbon aerogel synthesized at ambient conditions as a support and methods of cobalt-doped carbon aerogel on its physicochemical properties have been investigated. Carbon aerogel was synthesized by resorcinol and formaldehyde precursors at pyrolysis temperatures of 550 °C, 700 °C and 900 °C and cobalt-doped carbon aerogel was prepared by the following three different methods (i) cobalt impregnation on the carbon aerogel, (ii) cobalt impregnation on the organic resorcinol-formaldehyde aerogel, and (iii) addition of cobalt precursor to the initial resorcinol-formaldehyde mixture before carbon aerogel polymerization process. The results indicated that pyrolysis at 700 °C led to mesoporous carbon aerogel with a specific surface area of 483.8 m2/g. High cobalt dispersion and particle size controllability have been seen in the impregnation method, while in the third method, the cobalt precursor catalyzes the polymerization process and leads to the formation of microparticles.

The effects of changing ligand structures of cobalt complexes as electrolytes on the performance of the dye-sensitized solar cell were investigated. In this paper, cobalt(II/III) tris(2,2′-bipyridine), cobalt(II/III) tris(4,4′-dimethyl-2,2′-bipyridine) and cobalt(II/III) tris(4,4´-dimethoxy-2,2′-bipyridine) complexes as electrolytes in conjugate with organic dye D149 were investigated to consider the correlation of the cobalt complexes structural on the efficiency of the dye-sensitized solar cell. The Voc values of the prepared cells are related to the redox potential of their complexes and the maximum Voc was observed with cobalt(II/III) tris(2,2′-bipyridine) electrolyte. The obtained results represented that the cobalt(II/III) tris(4,4´-dimethyl- 2,2′-bipyridine) electrolyte has the highest efficiency in the solar cell compared with other cobalt complexes. These observed results have been interpreted by a possible interaction between the dye and cobalt complexes, which is more pronounced in the cobalt(II/III) tris(4,4´-dimethoxy- 2,2′-bipyridine) cell. This interaction should be fine-tuning with the structure of dye and complex to increase the efficiency of the dye-sensitized solar cell. In addition, the results demonstrated that a thinner layer of the TiO2 film decrease both the effects of mass transport issues and the charge recombination, therefore, it has significant advantages for cobalt electrolyte.