. 2023 Mar 26;13(4):379. doi: 10.3390/membranes13040379

Table 2.

Overview of the physicochemical characteristics of draw agents utilized in FO applications.

Type of Membrane	Type of Draw Agent	Concentration	Osmotic Pressure	Configuration	FO Performance		Regeneration Methods	Application	Advantages	Disadvantages	Reference
Type of Membrane	Type of Draw Agent	Concentration	Osmotic Pressure	Configuration	Jw; LMH	Js; gMH	Regeneration Methods	Application	Advantages	Disadvantages	Reference
CA	Polyacrylic acid sodium salt (PAA-Na (Mw = 1200))	0.72 g/mL	44 atm	AL–DS	22	0.17	UF	Wastewater treatment	High water flux, low RSF, and high water solubility	High viscosity, low solute diffusion, expensive precursors, and UF requires energy	[10]
CTA	Sodium alginate sulfonate	600 gNaLS/kg	78 bar	AL–FS AL–DS	8.5 15	12.3 27	NF	Desert Restoration	High osmotic pressure	Limited applications and relatively low water flux	[11]
TFC	Na₃PO₄	0.2 M	580 mOsm/kg	AL–FS AL–DS	9.02 16.2	0.95 1.3	MD	Activated sludge	Low RSF and high water solubility	Relatively low FO performances, complicated and energy-intensive recovery	[22]
CTA	EDTA sodium (pH = 8)	0.8 M	—	AL–DS	12.9	0.32	NF	Sludge dewatering	Low energy consumption, high water flux, and low RSF	Expensive solute and low solute rejection with NF recovery	[25]
CTA–non-woven	MgCl₂	1 M	—	AL–FS	6.3	—	—	Secondary treated effluents	High water flux and high rejection for nutrients up to 97%	High viscosity, high ICP, low diffusion coefficient, and contain scale precursor ions ( ${Mg}^{2 +}$ )	[26]
CTA–woven	Triethylenetetramine hexapropionic acid sodium (TTHP-Na (pH = 8))	0.5 g/mL	165 bar	AL–FS AL–DS	12.87 23.07	0.7 0.75	NF	Dye wastewater treatment	High osmotic pressure and average water flux	NF requires energy	[47]
CTA	KHCO₃	1.4 M	2.8 MPa	AL–FS	5.54	1.2	RO	Desalination	Low RSF	Limited applications, and contain scale precursor ions ( ${CO}_{3}^{2 -}$ ) and not easily recovered by RO	[102]
CTA	KBr	0.6 M	2.8 MPa	AL–FS	10.22	22	RO	Desalination	—	Very high RSF and high replenishment cost	[102]
CTA–nylon mesh	NH₄HCO₃	3.6 M	—	AL–FS AL–DS	7 9	—	Moderate heating	Desalination	High osmotic pressure capable of desalinating seawater and high FO performances	Low solubility and ammonia smell in water, high RSF, contain scale precursor ions ( ${CO}_{3}^{2 -}$ ), high replenishment cost, and not thermally stable	[105]
CTA–polyester screen	NaCl	0.6 M	27.44 bar	AL–FS	6.3	7.25	—	Desalination	High osmotic pressure, high solubility, low viscosity, and low cost	High RSF and high fouling tendency	[106]
CTA–polyester screen	NaHCO₃	0.72 M	26.91 bar	AL–FS	5.81	2.85	—	Desalination	Low cost	Low water solubility and contain scale precursor ions ( ${CO}_{3}^{2 -}$ )	[106]
CTA	KCl	2 M	89.3 bar	AL–FS	15.2	26.8	Direct fertigation	Fertilizer	High osmotic pressure, high solubility, low viscosity, and low cost	High RSF and high fouling tendency	[107]
TFC–polyamide	NH₄Cl	0.5 M	21.881 atm	AL–FS AL–DS	9.87 15.37	—	—	Desalination	Diluted draw solution could be directly used in irrigation	High RSF	[108]
TFC–polyamide	NaNO₃	0.5 M	21.3 atm	AL–FS AL–DS	7.97 14.26	—	—	Desalination	Diluted draw solution could be directly used in irrigation	High RSF and high biofouling tendency	[108]
TFC–polyamide	KNO₃	0.5 M	20.125 atm	AL–FS AL–DS	9 13.83	—	—	Desalination	Diluted draw solution could be directly used in irrigation	High RSF, high biofouling tendency, toxic and energy-intensive	[108]
TFC–polyamide	NH₄NO₃	0.5 M	17.764 atm	AL–FS AL–DS	7.9 11.88	—	—	Desalination	Diluted draw solution could be directly used in irrigation	High RSF and contain scale precursor ions ( ${CO}_{3}^{2 -}$ )	[108]
TFC–polyamide	Ca(NO₃)₂	0.5 M	26.491 atm	AL–FS AL–DS	8.21 15.41	—	—	Desalination	Diluted draw solution could be directly used in irrigation	Contain scale precursor ions ( ${Ca}^{2 +}$ ), high replenishment cost, and poor water extraction capacity	[108]
TFC–polyamide	CaCl₂	0.5 M	34.983 atm	AL–FS AL–DS	8.8 16.32	—	—	Desalination	High water flux and diluted draw solution could be directly used in irrigation	High RSF and contains scale precursor ions ( ${Ca}^{2 +}$ )	[108]
TFC	Na₂SO₄	1 M	—	AL–FS AL–DS	15.7 23.26	4.9 7.1	—	Desalination	High water flux	High RSF and contain scale precursor ions ( ${SO}_{4}^{2 -}$ )	[109]
TFC–polyamide	MgSO₄	1 M	—	AL–FS	11	1.32	Direct fertigation	Fertilizer	Higher diffusivity and does not require energy for recovery	Low FO performances, high viscosity, low water solubility, contain scale precursor ions ( ${SO}_{4}^{2 -}$ ) and reaction products are toxic and expensive reagents	[110]
TFC–polyamide	Mg(NO₃)₂	1 M	84 bar	AL–FS	30.8	24.18	Direct fertigation	Fertilizer	High osmotic pressure, high water flux, and does not require energy for recovery	High RSF	[110]
CA–polyester woven	(NH₄)₂SO₄	2 M	92.1 atm	AL–FS	19.41	2.6	Direct fertigation	Fertilizer	High osmotic pressure and does not require energy for recovery	Contains scale precursor ions ( ${SO}_{4}^{2 -}$ ) and high replenishment cost	[111]
CA–polyester woven	NH₄H₂PO₄	2 M	86.3 atm	AL–FS	16.65	28.7	Direct fertigation	Fertilizer	Diluted draw solution could be directly used	Low water flux and high biofouling tendency	[111]
CA–polyester woven	(NH₄)₂HPO₄	2 M	95 atm	AL–FS	14.01	4.6	Direct fertigation	Fertilizer	Diluted draw solution could be directly used	Low water flux and high biofouling tendency	[111]
CTA	NaH₂PO₄	22 g/L	23.73 bar	AL–FS	2.63	0.12	Direct fertigation	Fertilizer	Low RSF and does not require energy for recovery	Low water flux	[112]
CA	Sucrose	1 M	26.7 atm	AL–FS	12.9	—	NF	Wastewater treatment	Large molecule and high water solubility	Low osmotic pressure, low water flux, NF requires energy and relatively low FO performances	[113]
CA	Glucose	—	—	—	—	—	—	—	Large molecule and high water solubility	Low osmotic pressure, high ICP effect, and used only for emergency water supply	[114]
TFC	Poly(maleic acid) sodium (PMAS)	0.5 mol/kg	143 bar	AL–FS AL–DS	23.5 30.6	0.6 0.68	NF	Desalination	High osmotic pressure, big molecular size, high FO performance, and negligible RSF	NF requires energy	[115]
TFC–polyamide	Cobaltic complex (Na-Co-CA)	1 M	—	AL–FS	11.5	—	MD or NF	Heavy metal wastewater treatment	High osmotic pressure, high water flux, low RSF, low replenishment cost, minimize TDS in FS, and efficiency of waste water treatment	Recovery requires energy	[116]
CA	Cu complex (Cu-CA)	1 M	—	AL–FS AL–DS	8.53 15.16	0.08 0.11	—	Seawater desalination	High FO performance and negligible RSF	Complicated preparation	[117]
CA	Fe complex (Fe-CA)	1 M	—	AL–FS AL–DS	10.78 21	0.12 0.14	—	Seawater desalination	High FO performance and negligible RSF	Complicated preparation	[117]
TFC	Poly(aspartic acid sodium salt) (PAsp-Na)	0.3 g/mL	51.5 atm	AL–FS AL–DS	8.13 16.62	1.64 2.28	MD and NF	Wastewater reclamation Brackish water desalination	Low RSF, inhibits the scaling formation, and nontoxic	Average FO performances and recovery require energy	[118]
TFC	Polyamidoamine with terminal carboxyl groups (PAMAM-COONa (2.5 G))	0.5 g/mL	3603 mOsm/kg	AL–DS	29.7	7.5	MD	Wastewater treatment and protein enrichment	High osmotic pressure, low viscosity, relatively large molecular size, and low RSF	Low water flux tested only in AL–DS mode and not feasible	[119]
TFC	Poly(sodium4-styrene sulfonate) (PSS (Mw = 1200))	0.24 g/mL	—	AL–DS	18.2	5.5	UF	—	High osmotic pressure, low viscosity and high water flux	High RSF, lower diffusion coefficient, more severe CP, 40% water flux reduces after the regeneration and requires energy for UF	[120]
CTA	Poly(isobutylene-alt-maleic acid) sodium salt (PIMA-Na)	0.375 g/mL	—	AL–DS	34	0.196	MD	Seawater desalination	Low RSF and nontoxic	Relatively low FO performances, high viscosity, and low water flux when tested with seawater	[121]
CTA	Thermo-responsive PNIPAM/γ-PGA/PEG hydrogel	—	—	AL–FS	1.99	—	Heat in a water bath at 40 °C	Desalination	Low energy consumption and negligible RSF	Poor water flux	[122]
CTA-polyester mesh	Electric-responsive HA/PVA hydrogel (6 V)	—	—	AL–FS	25.49	—	Electric field at 6 V	Desalination	High water flux, negligible RSF, and more safe and efficient when regenerating drinking water	___	[123]