Super-adsorbing porous thermo-responsive desiccants
Thermo-responsive hydrogel composite (TRHC) desiccants having high adsorption capacities, fast adsorption/desorption rates, and low regeneration temperatures (T reg ) compared to traditional desiccants. TRHC desiccants may be synthesized by freeze drying. The porous structures resulting from freeze drying copolymers of thermo-responsive polymers and/or hygroscopic agents may be combined with hygroscopic inorganic salts, resulting in TRHC desiccants having superior performance properties.
1. A composition of a thermo-responsive desiccant, the composition comprising:
a thermo-responsive polymer comprising N-isopropylacrylamide (NIPAAm);
a hygroscopic agent comprising sodium acrylate (SA); and
a crosslinker comprising N,N′-methylenebisacrylamide (MBAA); wherein:
the thermo-responsive desiccant has a lower critical solution temperature (LCST) transition,
the thermo-responsive desiccant is configured to adsorb a water at a temperature below the LCST transition,
the thermo-responsive desiccant is configured to desorb the water at a temperature above the LC ST transition, and
the LCST transition is approximately 50° C.
2. The composition of claim 1 , wherein:
a main chain comprising the thermo-responsive polymer is covalently bonded to a plurality of side chains comprised of the hygroscopic agent forming a grafted polymer.
3. The composition of claim 1 , wherein:
the thermo-responsive polymer is interlaced with the hygroscopic agent forming an interpenetrating network, and
the hygroscopic agent is not covalently bonded to the hygroscopic agent.
4. The composition of claim 1 , wherein:
the thermo-responsive polymer is covalently bonded to the hygroscopic agent, resulting in a copolymer.
5. The composition of claim 1 , wherein the thermo-responsive polymer further comprises at least one of poly[2-dimethylamino]ethyl methacrylate, hydroxypropylcellulose, poly(vinylcaprolactame), poly-2-isopropyl-2-oxazoline, or polyvinyl methyl ether.
6. The composition of claim 1 , wherein the hygroscopic agent further comprises an inorganic salt.
7. The composition of claim 6 , wherein the inorganic salt comprises at least one of calcium chloride (CaCl 2 ), lithium chloride (LiCl), aluminum chloride (AlCl 3 ), sodium chloride (NaCl), sodium nitrate (NaNO 3 ), sodium hydroxide (NaOH), potassium nitrate (KNO 3 ), potassium chloride (KCl), potassium carbonate (K 2 CO 3 ), potassium sulfate (K 2 SO 4 ), a potassium phosphate, potassium hydroxide (KOH), magnesium chloride (MgCl 2 ), magnesium nitrate (Mg(NO 3 ) 2 ), magnesium sulfate (MgSO 4 ), magnesium iodide (MgI 2 ), calcium chloride (CaCl 2 ), calcium nitrate (Ca(NO 3 ) 2 ), zinc chloride (ZnCl 2 ), zinc nitrate (ZnNO 3 ), zinc sulfate (ZnSO 4 ), iron chloride (FeCl 3 ), lithium bromide (LiBr), or lithium chloride (LiCl).
8. The composition of claim 1 , wherein the hygroscopic agent further comprises at least one of poly(sodium 4-styrenesulfonate), chlorine-doped polypyrrole (PPy-Cl), a sodium polyacrylate, poly(ethylene oxide), an alginate, or a cross-linked bipolar polymer.
9. The composition of claim 1 , wherein the crosslinker further comprises at least one of N,N′-ethylenebisacrylamide, N,N′-propylenebisacrylamide, polyethylene glycol diacrylate, divinylbenzene (para, ortho, meta), bis(2-methacryloyl)oxyethyl disulfide, 1,4-Bis(4-vinylphenoxy)butane, or triethylene glycol dimethacrylate.
10. The composition of claim 1 , wherein:
the thermo-responsive desiccant has an adsorption capacity between about 1.5 g moisture/g composition and about 4 g moisture/g composition when at a temperature below the LCST transition.
11. The composition of claim 1 , wherein:
the thermo-responsive desiccant has an adsorption rate between greater than 0 g moisture/g composition-hour and about 3 g moisture/g composition-hour when at a temperature below the LCST transition.
12. The composition of claim 1 , wherein:
the thermo-responsive desiccant has a desorption rate between greater than 0 g moisture/g composition-hour and about 3 g moisture/g composition-hour when at a temperature above the LCST transition.
13. A device configured to remove a water from a substantially continuous sheet, the device comprising:
a thermo-responsive desiccant; and
a drum comprising the thermo-responsive desiccant; wherein:
the thermo-responsive desiccant comprises:
a thermo-responsive polymer comprising N-isopropylacrylamide (NIPAAm);
a hygroscopic agent comprising sodium acrylate (SA); and
a crosslinker comprising N,N′-methylenebisacrylamide (MBAA); wherein:
the thermo-responsive desiccant has a lower critical solution temperature (LCST) transition,
the thermo-responsive desiccant is configured to adsorb a water at a temperature below the LCST transition,
the thermo-responsive desiccant is configured to desorb the water at a temperature above the LCST transition,
the LCST transition is approximately 50° C.,
the drum is configured to rotate and direct the substantially continuous sheet through a first zone and a second zone,
while in the first zone, the thermo-responsive desiccant is configured to adsorb at least a portion of the water contained in the substantially continuous sheet at a temperature below the LCST transition,
while in the second zone, the thermo-responsive desiccant is configured to desorb the water at a temperature above the LC ST transition, and
the water is desorbed in a liquid phase.
14. The device of claim 13 , wherein the substantially continuous sheet is a paper pulp.
15. A device configured to remove a water from a granular material, the device comprising:
a thermo-responsive desiccant;
a first drum comprising the thermo-responsive desiccant;
a second drum comprising the thermo-responsive desiccant; wherein:
the thermo-responsive desiccant comprises:
a thermo-responsive polymer comprising N-isopropylacrylamide (NIPAAm);
a hygroscopic agent comprising sodium acrylate (SA); and
a crosslinker comprising N,N′-methylenebisacrylamide (MBAA); wherein:
the thermo-responsive desiccant has a lower critical solution temperature (LCST) transition,
the thermo-responsive desiccant is configured to adsorb a water at a temperature below the LCST transition,
the thermo-responsive desiccant is configured to desorb the water at a temperature above the LCST transition,
the LCST transition is approximately 50° C.,
the first drum and the second drum are positioned adjacent to each other to form a gap between the first drum and the second drum,
the first drum rotates in a clockwise direction and the second drum rotates in a counterclockwise direction,
the gap is configured to receive the granular material,
each drum is configured to be operated at a temperature below the LCST while at least in the gap, such that at least a portion of the water adsorbed by the thermo-responsive desiccant and removed from the granular material,
each drum is configured to rotate and direct the substantially continuous sheet through a first zone and a second zone,
while in the first zone, the thermo-responsive desiccant is configured to adsorb at least a portion of the water contained in the substantially continuous sheet at a temperature below the LCST,
while in the second zone, the thermo-responsive desiccant is configured to desorb the water at a temperature above the LCST,
each drum is configured to rotate to the second zone operated at a temperature above the LCST, such that the water is desorbed from the thermo-responsive desiccant, and
the water is desorbed in the liquid phase.
16. The device of claim 15 , wherein:
the granular material comprises a food product.