NF has properties between RO and UF, which can enable separation in the molecular range of 100–1000 Da [71] and [72], as well as high salt rejection caused by the charge effect [73] and [74]. The charge effect can result in the removal of ions (most of which are multivalent), while uncharged organic components may be separated by size exclusion [75]. In the past years, the application of NF has become popular, because of offering a variety of advantages such as low operating pressure, relatively low capital and maintenance cost, and high rejection rates for multivalent salts [72] and [76]. For example, as high as 99% rejection rate for divalent salts in solution could be achieved by NF [77].
Tan and Ng [78] investigated the suitability of NF to recover selected DSs (i.e., MgCl2, MgSO4, Na2SO4, C6H12O6) after FO. A water flux of ∼10 LMH in both FO and NF processes could be observed. The salt rejection rates for the selected DSs could achieve a maximum of 97.9%. The product water obtained had a total dissolved solids (TDS) content of 113.6 mg/L and met the drinking water TDS standard of 500 mg/L set by the World Health Organization [78]. Zhao et al. [79] employed NF to regenerate divalent DSs (e.g. Na2SO4 or MgSO4) after FO. Results demonstrated that this hybrid FO–NF process could offer many benefits over the standalone RO process for desalination of brackish water, such as lower operating pressure, less flux decline caused by membrane fouling, higher flux recovery after cleaning, higher permeate quality, and obviated requirement for pretreatment and chemical cleaning. Su et al. [80] used NF to recover the dilute sucrose with a large molecule size to produce clean water after FO for wastewater treatment. As high as 99.6% rejection of sucrose could be achieved by the NF process. Preferably, the production rates of FO and NF processes could be balanced. Hau et al. [32] indicated that the NF recovery (pressure of 5.5 bar) of EDTA sodium salts exhibiting high charged compounds performed well, and had a high salt rejection of 93%. Ge and Chung [31] also used NF to regenerate hydroacid complexes after FO, which had expanded configurations and charged groups. A low pressure of 10 bar was utilized in the NF cell, and a high rejection of more than 90% was achieved. In general, the NF process for recovery may be a good option especially when the DSs with multivalent ions are used due to its relatively low operating pressure and high salt rejection.
NF มีคุณสมบัติระหว่าง RO และ UF ซึ่งสามารถช่วยให้แยกในช่วงโมเลกุลของ 100 – 1000 ดา [71] [72], และการปฏิเสธเกลือสูงที่เกิดขึ้นด้วยผลค่า [73] [74] ผลค่าอาจส่งผลในการกำจัดประจุ (ซึ่งส่วนใหญ่เป็น multivalent), ในขณะที่ส่วนประกอบอินทรีย์ uncharged อาจแยกจากกัน โดยแยกขนาด [75] ในปีผ่านมา แอพลิเคชันของ NF ได้กลายเป็นที่นิยม เนื่องจาก มีข้อดีเช่นความดันต่ำทำงานหลากหลาย ค่อนข้างต่ำทุน และต้นทุนการบำรุงรักษา และอัตราการปฏิเสธสูง multivalent เกลือ [72] และ [76] ตัวอย่าง สูงเท่าอัตราการปฏิเสธ 99% เกลือ divalent ในโซลูชันอาจทำได้ โดย NF [77]Tan and Ng [78] investigated the suitability of NF to recover selected DSs (i.e., MgCl2, MgSO4, Na2SO4, C6H12O6) after FO. A water flux of ∼10 LMH in both FO and NF processes could be observed. The salt rejection rates for the selected DSs could achieve a maximum of 97.9%. The product water obtained had a total dissolved solids (TDS) content of 113.6 mg/L and met the drinking water TDS standard of 500 mg/L set by the World Health Organization [78]. Zhao et al. [79] employed NF to regenerate divalent DSs (e.g. Na2SO4 or MgSO4) after FO. Results demonstrated that this hybrid FO–NF process could offer many benefits over the standalone RO process for desalination of brackish water, such as lower operating pressure, less flux decline caused by membrane fouling, higher flux recovery after cleaning, higher permeate quality, and obviated requirement for pretreatment and chemical cleaning. Su et al. [80] used NF to recover the dilute sucrose with a large molecule size to produce clean water after FO for wastewater treatment. As high as 99.6% rejection of sucrose could be achieved by the NF process. Preferably, the production rates of FO and NF processes could be balanced. Hau et al. [32] indicated that the NF recovery (pressure of 5.5 bar) of EDTA sodium salts exhibiting high charged compounds performed well, and had a high salt rejection of 93%. Ge and Chung [31] also used NF to regenerate hydroacid complexes after FO, which had expanded configurations and charged groups. A low pressure of 10 bar was utilized in the NF cell, and a high rejection of more than 90% was achieved. In general, the NF process for recovery may be a good option especially when the DSs with multivalent ions are used due to its relatively low operating pressure and high salt rejection.
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