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An in-situ mitigation method for forward osmosis membrane fouling based on removal of calcium and magnesium ions

A technology of forward osmosis membrane and calcium and magnesium ions, applied in the direction of osmosis/dialysis water/sewage treatment, semi-permeable membrane separation, chemical instruments and methods, etc., can solve problems such as not fully applicable to FO membranes, focus on ectopic control, etc., and achieve Removes effects with good effect, reduces processing cost, removes effects with high efficiency

Active Publication Date: 2020-04-17
JIANGNAN UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Therefore, the relatively mature MF or UF membrane fouling control methods, such as chemical cleaning, can alleviate FO membrane fouling to a certain extent, but they are not completely suitable for FO membranes.
In addition, the existing FO membrane pollution control methods all focus on the way of ex-situ control

Method used

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  • An in-situ mitigation method for forward osmosis membrane fouling based on removal of calcium and magnesium ions
  • An in-situ mitigation method for forward osmosis membrane fouling based on removal of calcium and magnesium ions
  • An in-situ mitigation method for forward osmosis membrane fouling based on removal of calcium and magnesium ions

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0044] Embodiment 1: (the absorption of calcium by DGT technology)

[0045] The object of this embodiment is the FO membrane polluted by sodium alginate-calcium sulfate (calcium ion concentration is 1mM, 15mM, 35mM), and its operating performance after DGT adsorption is: the DGT adsorption rate can reach up to 62.83%. Water flux has been increased by up to 70%. The specific operation steps are as follows:

[0046] (1) Prepare the polluted FO membrane in the FO sewage treatment plant.

[0047] (2) Prepare the DGT adsorption device, and soak the adsorption film in 0.03M NaCl at 4°C for 16 hours to complete the activation process.

[0048] (3) Install the DGT adsorption device, and install the adsorption membrane, diffusion membrane and filter membrane in order from top to bottom.

[0049] (4) DGT was used to remove calcium ions in pollutants in situ. The filter membrane in the DGT device was in contact with the FO-contaminated membrane surface for 48 hours.

[0050](5) Perfo...

Embodiment 2

[0056] Embodiment 2 (EDTA membrane is to the adsorption performance of calcium ion)

[0057] The object of this example is the FO membrane polluted by sodium alginate-calcium sulfate (calcium ion concentration is 1mM, 15mM, 35mM), and its operating performance after being adsorbed by EDTA membrane is: EDTA adsorption rate can reach up to 93.51% , the highest recovery of water flux is 77.1%. The specific operation steps are as follows:

[0058] (1) Prepare the polluted FO membrane in the FO sewage treatment plant.

[0059] (2) Preparation of EDTA adsorption film: add 1 wt% EDTA-2Na to water at 95°C, add 3 wt% agar, stir evenly, and cool to prepare EDTA adsorption film.

[0060] (3) The EDTA adsorption membrane was used to remove the calcium ions in the pollutants in situ, and the adsorption time was 24h.

[0061] (4) Perform in-situ backwashing on the FO contaminated membrane after EDTA adsorption, using 0.5M sodium chloride solution as the raw material solution, deionized w...

Embodiment 3

[0067] Embodiment 3 (EDTA membrane is to the adsorption performance of calcium ion)

[0068] The preparation method of the EDTA membrane in this example is: dissolve 2wt% EDTA-2Na in water at 95°C, add 4.5wt% agar, stir evenly, and cool the prepared EDTA adsorption membrane. The remaining operations and conditions are the same as in Example 2 same.

[0069] Taking the FO membrane polluted by sodium alginate-calcium sulfate (1mM calcium ion concentration) as an example, the water flux of the FO membrane after EDTA adsorption can recover up to 35.2%, and the adsorption rate of the EDTA adsorption membrane can reach up to 42.35%. The pollutant structure on the surface of the FO-contaminated membrane after adsorption changed, the membrane pores became loose, and the average biomass content on the membrane surface decreased.

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Abstract

The invention discloses a method for relieving forward osmosis (FO) pollution in situ based on calcium magnesium ion removal, and belongs to the technical fields of sewage treatment and membrane separation. The invention provides an FO membrane pollution control method for removing calcium magnesium ions from membrane surface pollutants in situ on the basis of consensus that the calcium magnesiumions reinforce FO membrane pollution. In particular, the calcium magnesium ions are extracted from the FO membrane surface pollutants in situ by virtue of a gradient film diffusive gradient thin filmtechnology (DGT) and the chelating effect on metal ions by ethylene diamine tetraacetic acid (EDTA), the content of the calcium magnesium ions in the membrane surface pollutants is reduced and the porosity of the membrane pollution layer is increased, so that the membrane surface resistance is reduced and the cleaning effect of the pollution membrane is improved. Compared with the traditional membrane pollution control measures, the method for relieving the FO membrane pollution in situ based on calcium magnesium ion removal is simpler to operate and avoids damage to the membrane; and the removing materials such as DGT and EDTA can be reused.

Description

technical field [0001] The invention relates to an in-situ method for alleviating forward osmosis membrane fouling based on the removal of calcium and magnesium ions, and belongs to the technical fields of sewage treatment and membrane separation. Background technique [0002] With the increasing water shortage problem, the forward osmosis (FO) process has received a lot of attention all over the world. FO membrane has outstanding advantages such as good retention performance, low energy consumption, and small pollution tendency. However, long-term operation and severe membrane fouling under anaerobic conditions have become bottlenecks restricting the popularization and application of FO membranes and related combined processes. [0003] FO membrane fouling mainly includes inorganic fouling, organic fouling and biological fouling. The fouling type is the same as that of traditional microfiltration (MF) or ultrafiltration (UF) membranes, but due to the difference in driving...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): B01D65/08C02F1/44
CPCB01D61/002B01D65/08B01D2321/04C02F1/445C02F2303/14C02F2303/22
Inventor 王新华李玲李秀芬任月萍
Owner JIANGNAN UNIV