Investigation of Electrodialysis Technology for Water Desalination

سال انتشار: 1396
نوع سند: مقاله کنفرانسی
زبان: انگلیسی
مشاهده: 350

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شناسه ملی سند علمی:

NRCCONF01_194

تاریخ نمایه سازی: 6 مهر 1397

چکیده مقاله:

Desalination is a process that removes dissolved minerals from seawater, brackish water, or treated wastewater. About 71% of the earth surface is covered by water which is in the form of the oceans, seas and the ices in the poles. However, only about 3% of water is fresh and suitable for drinking. The water of the oceans and seas is salty and thus not directly utilizable. Therefore, some special processes are needed to desalinate these waters. Meanwhile, copper, zinc, lead and chromium are Persistent, Bio accumulative and Toxic (PBT) chemicals. The PBT chemicals are of particular concern not only because they are toxic but also because they remain in the environment for long periods of time, are not readily destroyed, and build up or accumulate in body’s tissues. Relatively small releases of PBT chemicals can pose human and environmental health threats and consequently releases of these chemicals warrant recognition by communities. Hence, their eliminating from wastewater is of great importance. Pollution prevention has become a central part of the thinking for regulators, chemists, chemical engineers, process engineers and others in chemical manufacturing. Efforts have been undertaken to identify new processes that inherently produce less pollution to be used in tomorrow’s processing plants. New technologies such as membrane technologies to recover and reuse waste process streams are enjoying interest. ED with ion exchange membranes represents one of the most important membrane methods. It deals with the problems of desalination of salted waters, wastewater minimization, ultra-pure water production, concentration of dilute solutions, separation of electrolytes and non-electrolytes and production of acids and alkalis from their salts. The special features of electrodialysis are high water recovery, selective desalination, low chemical demand and low energy demand. The principle of electrodialysis involves the removal of ionic components from aqueous solutions through ion exchange membranes using the driving force of an electric field. The water to be treated is pumped through a membrane stack, which consists of alternately placed anionic and cationic selective membranes. Separated by gasket frames and spacers, the membranes are fixed between two end plates, which contain the electrodes producing the electric field. In order to transfer the electric current and to remove gases produced by the electrode reactions, the electrode chambers are rinsed with an electrolyte solution. In the compartments of the membrane stack, the ion content is diluted or concentrated according to the ion penetration through the membranes. Identical compartments are connected by a distributing and collecting system. Thus, the raw water is separated into a diluate and a brine stream. Both streams flow at the same velocity through the membrane stack. This cross-flow velocity has to be in a certain range, due to the ion transfer mechanisms to and from the membranes. As a rule, the water to be diluted passes the membrane stack once, whereas the brine stream is recycled. The brine concentration is adjusted by means of dilution with raw water. Thus, the brine stream is operated in a feed and bleed mode. In this study, application of electrodialysis technology in water desalination it was discussed.

نویسندگان

Hedieh Ahmadpari

M.Sc. Student of Irrigation and Drainage, University of Tehran

Maryam Taghavi

M.Sc. Student of Instrumental Analytical Chemistry, University of Duisburg-Essen Universitätsstraße ۵, ۴۵۱۴۱ Essen, Germany

Abed Tavazoei

M.Sc. Student of Instrumental Analytical Chemistry, University of Duisburg-Essen Universitätsstraße ۵, ۴۵۱۴۱ Essen, Germany