جستجوی مقالات مرتبط با کلیدواژه « purification » در نشریات گروه « فنی و مهندسی »

Using natural colors in the food and pharmaceutical industries is very important. Natural colorants obtained from animals, plants and microorganisms are a promising alternative to artificial food colors because synthetic colors have a negative effect on human health in the long term. Phycocyanin is used as a natural blue and water-soluble colorant instead of artificial blue food dyes, which, in addition to coloring food, have potential useful properties as antioxidants and anticancer agents and have received scientific and industrial attention. Phycocyanin is extracted from microalgae such as spirulina and has a health-giving role against various conditions such as cancer, anemia, inflammation, diabetes, obesity and neurological disorders. It has also gained popularity due to its various applications in various food and pharmaceutical industries. This research has discussed an overview of the biotechnological production of phycocyanin edible blue colorant from spirulina microalgae, microbial culture, extraction, purification, stability methods, and its applications.

Froth flotation is an effective method for separating fine solid particles from aqueous solutions based on surface properties. The most important phenomenon in this issue is the formation of solid-gas bubble accumulation. Appropriate selection of operating conditions such as size, shape, charge and hydrophobicity of nanoparticles, concentration, pH solution, flow rate and gas velocity, bubble size and flotation reagents such as surfactants for hydrophobicizing particles is essential to increase absorption by gas bubbles and collect them in the froth. In this article, an attempt has been made to examine the potential and limitations of the process of flotation of nanoparticles and their separation from solutions, or the use of nanoparticles as collectors, reinforcements and stabilizers of the froth, and the existing challenges and solutions to overcome them should be explained. According to the progress made in the field of equipment and reagents used, the flotation method could be a promising method to remove, separate, recover and purify nanoparticles from the solution.

Wastewaters containing heavy metals produced by industries has detrimental effects on the environment. One of the effective methods for removal of heavy metals is the use of adsorption method by nanoparticles. The aim of this study was to remove zinc and nickel elements from effluents of Tarom industrial Town of Zanjan using modified multi-walled carbon nanotubes. In this  descriptive-analytical study, effect of effective parameters such as contact time, adsorbent content, pH, temperature and concentration of metal ions on the removal efficiency of metals from Ni(II) and Zn(II) from wastewater and isotherm, kinetics and thermodynamic models of adsorption process was investigated. SEM and FTIR spectrums were taken to prove nanotubes and to determine adsorbent factor groups before and after preparation, respectively. The results of study showed that the absorption of Zn and Ni metals is highly dependent on pH. Study results showed that by increasing the pH of effluent up to the range of 8, and 7 for Ni(II) and Zn(II) metals, respectively, the removal percentage of metal ions increased and then decreased. By increasing in the adsorbent amount and contact time, the removal percentage of metal ions increased and by increasing the reaction temperature and concentration of metal ions in the effluent, the removal percentage of metal ions decreased. So that, the highest removal percentage of Ni(II) and Zn(II) ions was obtained in adsorbent value of 2 mg/L, contact time of 120 min, concentration of 100 mg/L and temperature of 15 °C. The results also showed that the adsorption of Ni(II) and Zn(II) metals from effluent follows Langmir isotherm absorption model and the adsorption kinetics is adapted to the second-order pseudo-reaction (R2>0.98), this mechanism is controlled by adsorption. Also, based on the obtained results, with increasing temperature, the free energy of Gibbs system standard decreased, which indicates the adsorption process is done spontaneously. The maximum adsorption capacity of nickel and zinc metals was 43 and 54 mg/g, respectively. According to the results, it is concluded that modified multi-walled carbon nanotubes have good ability to remove nickel and zinc from effluents and can be used in wastewater treatment containing heavy metals.

Dimethyl amino ethane azide (DMAZ) is a good replacement of hydrazine derivatives in aerospace industries. It is produced from the reaction between dimethyl amino ethyl chloride and aqueous sodium azide. DMAZ is formed in organic phase with a purity of at least 90%. High pure DMAZ is necessary for aerospace utilization. Thermal sensitivity of DMAZ leads the purification procedure to be performed at low temperatures. So, the Distillation at sub-atmospheric pressures is a good choice for this purpose. In this paper, effect of various parameters such as temperature and pressure on the distillation time and loss of material and final purity of DMAZ was studied in regular packed column, known as vigorous column, and optimized conditions were found.