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Using Zeolite membrane instead of polymeric membrane in water reverse osmosis process

عنوان مقاله: Using Zeolite membrane instead of polymeric membrane in water reverse osmosis process
شناسه (COI) مقاله: IPEC03_212
منتشر شده در سومین کنگره ملی مهندسی نفت در سال 1390
مشخصات نویسندگان مقاله:

Rouzbeh Markazi Movaqar

خلاصه مقاله:
In water treatment using reverse osmosis polymeric membrane is used in the water input pressure is high. Furthermore, this type of membrane can not be recycled. In this project, using zeolite membrane, types A, Y, and MFI in water treatment is investigated. In addition the performance of polymeric and zeolite membranes to remove organic compounds will be investigated. Finally, the maximum TDS in input water will be examined. A study on the reverse osmosis desalination of aqueous solutions using α-alumina-supported MFI-type zeolite membranes. A Na+ rejection of 76.7% with a water flux of about 0.112 kg m−2 h−1 was obtained for a 0.1 M NaCl feed solution under an applied pressure of 2.07 MPa. For a complex feed solution containing 0.1 M NaCl + 0.1 M KCl + 0.1 M NH4Cl + 0.1 M CaCl2 + 0.1 M MgCl2, rejections of Na+, K+, NH4+, Ca2+, and Mg2+ reached 58.1%, 62.6%, 79.9%, 80.7%, and 88.4%, respectively, with a water flux of 0.058 kg m−2 h−1, after 145 h of operation at an applied pressure of 2.4 MPa. Because of the extremely stable chemical, mechanical, and thermal properties, zeolite membranes show great advantages in difficult situations such as operations in a strong solvent environment, or those requiring high temperatures and high pressures. The influencing factors, including operating pressure, temperature, and ion concentration, on the RO performance of zeolite membranes are investigated. The charge density, size, and apparent dynamic hydration number of the ion as well as the mobility of the hydrated ion were found to have critical influences on ion diffusion and water permeation through the polycrystalline zeolite membrane. Zeolites are microporous aluminosilicate materials with extremely uniform pores defined by crystal structures. The effective pore sizes of the familiar 12-member ring FAU, 10-member ring MFI, and 8-member ring A zeolites are 0.74 nm, 0.56nm, and 0.42 nm, respectively. These subnanometer channels are sufficiently large for transport of water molecules (dynamic size ~0.29 nm). In aqueous solutions, both cations and anions form hydrated complexes with ―cluster‖ sizes larger than the zeolite pores. For example, the hydrated Na+ ions,3[Na(H2O)n]+, have effective sizes of 0.8 – 1.0 nm, which is too large to enter the small-pore zeolites such as A and MFI types.

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