Photoswitchable guanidinium compounds for removal of oxyanions from liquid solutions
A compound having the following structure: wherein: R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 , and R 10 are independently selected from (i) hydrogen atom, (ii) hydrocarbon groups (R) containing 1-30 carbon atoms and optionally substituted with one or more fluorine atoms, (iii) —OR′ groups, (iv) —NR′ 2 groups, (v) —C(O)R′ groups, and (vi) halogen atoms, wherein R′ groups are independently selected from R groups and hydrogen atoms, and wherein the R group optionally includes a C(O), ether, or amino linkage; X m− is an anionic species with a magnitude of charge m, where m is an integer of at least 1; and n is a number, provided that n×m=1. Also described herein are methods for removing one or more oxyanions from a liquid source by use of the above compound or mono-pyridyl derivative thereof.
1 . A compound having the following structure:
wherein:
R 1 , R 2 , R 4 , R 5 , R 6 , and R 8 are hydrogen atom;
R 9 and R 10 are independently selected from hydrogen atom and methyl;
X m− is an anionic species with a magnitude of charge m, where m is an integer of at least 1;
R a and R b are linear or branched alkyl or alkenyl groups containing 1-30 carbon atoms; and
n is a number, provided that n×m=1.
2 . The compound of claim 1 , wherein R 9 and R 10 are hydrogen atoms.
3 . The compound of claim 1 , wherein X m− is a halide.
4 . The compound of claim 1 , wherein X m− is an oxyanion.
5 . A method for removing an oxyanion from a liquid source, the method comprising contacting said liquid source with an oxyanion precipitating compound having the following structure:
to result in precipitation of a salt of said oxyanion precipitating compound and oxyanion;
wherein:
R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 , and R 10 are independently selected from (i) hydrogen atom, (ii) hydrocarbon groups (R) containing 1-30 carbon atoms and optionally substituted with one or more fluorine atoms, (iii) —OR′ groups, (iv) —NR′ 2 groups, (v) —C(O) R′ groups, and (vi) halogen atoms, wherein R′ groups are independently selected from R groups and hydrogen atoms;
at least one of R 1 , R 2 , R 3 , and R 4 in Formula (2) is selected from groups (iii)-(vi) provided above;
X m− is an anionic species with a magnitude of charge m, where m is an integer of at least 1, provided that X m− is an anionic species exchangeable with the oxyanion in said liquid source before said oxyanion precipitating compound contacts said liquid source, and X m− is said oxyanion in said salt; and
n is a number, provided that n×m=1.
6 . The method of claim 5 , wherein said oxyanion is selected from the group consisting of sulfate, nitrate, selenate, tellurate, phosphate, arsenate, carbonate, bicarbonate, perchlorate, and metal oxyanions.
7 . The method of claim 5 , wherein said oxyanion is sulfate or phosphate.
8 . The method of claim 5 , wherein X m− is halide or nitrate before said oxyanion precipitation compound contacts said liquid source.
9 . The method of claim 5 , wherein the oxyanion precipitating compound has the structure of Formula (1).
10 . The method of claim 9 , wherein R 9 and R 10 are hydrogen atoms.
11 . The method of claim 9 , wherein at least one of R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 , and R 10 is selected from R, —OR′, —NR′ 2 , and —C(O)R′.
12 . The method of claim 9 , wherein at least one of R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , and R 8 is an —OR′ group.
13 . The method of claim 12 , wherein the compound has the following structure:
wherein R 1 , R 2 , R 4 , R 5 , R 6 , R 8 , R 9 , and R 10 are as defined in claim 1 , and R a and R b are linear or branched alkyl or alkenyl groups containing 1-30 carbon atoms.
14 . The method of claim 9 , wherein, following precipitation of the salt, the salt is removed from the liquid source, transferred to a second liquid, and the salt is exposed to electromagnetic radiation in the second liquid to isomerize the compound of Formula (1) to a closed (Z,Z) form having the following structure:
with simultaneous release of the oxyanion and dissolution of an uncomplexed form of the closed oxyanion precipitating compound according to Formula (1′) in the second liquid or partitioning of an uncomplexed form of the closed oxyanion precipitating compound according to Formula (1′) in a third liquid in contact with the second liquid.
15 . The method of claim 14 , wherein the uncomplexed form of the closed oxyanion precipitating compound is thermally converted back to the structure of Formula (1).
16 . The method of claim 15 , wherein, after thermal conversion, the oxyanion precipitating compound of Formula (1) is re-used in a subsequent process of removing an oxyanion from a liquid source.
17 . The method of claim 14 , wherein the electromagnetic radiation has a wavelength below 600 nm.
18 . The compound of claim 1 , wherein R a and R b are linear or branched alkyl or alkenyl groups containing 2-30 carbon atoms.
19 . The compound of claim 1 , wherein R a and R b are linear or branched alkyl or alkenyl groups containing 3-30 carbon atoms.