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

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.

Lack of water is considered the most important threat to the survival of human beings and natural ecosystems. Food and energy security, health and industrial progress, which are the main components of the sustainable development of societies, depend on water more than anything else. Water consumption in Loshan power plant is 2600 L/MWh raw water, which is very high compared to the production capacity and is due to having a tower in its cooling system. Considering the high volume of water consumed in this power plant compared to the production efficiency and on the other hand, reducing the amount of rainfall and droughts that have occurred, it is necessary to provide a solution to modify the consumption pattern for this power plant. Considering the special position of this power plant, solutions to modify the water consumption pattern by recycling clean drains (blow down of boilers, back wash of sand filters and water sampling), purification and recycling the blow down of cooling towers into the water cycle and optimization of cooling towers (replacing drippers, replacing nozzles and optimizing water distribution to increase efficiency, using a rotating nozzle to increase the time and speed of the water droplets hitting the air in order to transfer more heat) are suggested. According to the experimental data, the conductivity of boiler blowdown is about 10 μs/cm and the expenses of recycling the blowdown of boiler by using heat exchanger is estimated about 324.425.000 Rials.

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.