Preparation of hydrous graphene oxide for use as a concrete admixture
An aqueous dispersion of graphene oxide is prepared in an additive process by subjecting graphitic carbon, such as biochar, in water or an aqueous solution to a high-shear environment in the presence of a dispersing agent to exfoliate graphene oxide. An intercalating agent may be added to facilitate exfoliation, and optionally neutralized. The graphitic carbon may be pre-processed by wet milling prior to exfoliation. The aqueous dispersion of graphene oxide may be used as a concrete admixture in a concrete composition.
1 . A process for manufacturing an aqueous dispersion of graphene oxide, the process comprising:
subjecting biochar in a solvent, the solvent comprising water, to a high-shear rotor-stator mixing environment in the presence of a dispersing agent to exfoliate graphene oxide.
2 . The process of claim 1 , wherein the solvent is water, the process further comprising the step of adding the dispersing agent to the biochar in the solvent prior to subjecting the biochar to exfoliation in the high-shear rotor-stator mixing environment.
3 . The process of claim 2 , further comprising, prior to the step of adding the dispersing agent, the step of wet-milling the biochar.
4 . The process of claim 1 , further comprising the step of adding an intercalating agent to the biochar in the solvent prior to or concurrently with subjecting the biochar in the solvent to the high-shear rotor-stator mixing environment.
5 . The process of claim 4 , wherein the intercalating agent comprises a basic intercalating agent, and the intercalating agent is added prior to subjecting the biochar in the solvent to exfoliation in the high-shear rotor-stator mixing environment, the process further comprising the steps of performing a first exfoliation of the biochar in the solvent in the presence of the intercalating agent to provide exfoliated graphene oxide in the solvent and adding a neutralizing agent, prior to subjecting the exfoliated graphene oxide to the high-shear rotor-stator mixing environment in a further exfoliation step.
6 . The process of claim 5 , wherein the intercalating agent comprises at least one of potassium hydroxide, sodium hydroxide, and lithium hydroxide.
7 . The process of claim 6 , wherein the intercalating agent comprises potassium hydroxide.
8 . The process of claim 5 , wherein the neutralizing agent comprises an acid.
9 . The process of claim 8 , wherein adding the neutralizing agent comprises sparging the exfoliated graphene oxide in the solvent with carbon dioxide.
10 . The process of claim 1 , wherein the step of subjecting the biochar in the solvent to the high-shear rotor-stator mixing environment comprises circulating the biochar in the solvent through the high-shear rotor-stator mixing environment and a tank reactor using a pump, wherein the high-shear rotor-stator mixing environment comprises a high-shear wet mill.
11 . The process of claim 1 , wherein the solvent is water.
12 . The process of claim 1 , wherein the dispersing agent comprises lignosulfonate.
13 . The process of claim 1 , wherein the dispersing agent comprises polycarboxylate ether.
14 . The process of claim 1 , wherein the dispersing agent comprises a composition of at least polycarboxylate ether and lignosulfonate.
15 . The process of claim 10 , further comprising, after circulating the biochar in the solvent:
measuring a concentration or particle size distribution of graphene oxide in the aqueous dispersion; and
further circulating the graphene oxide in the aqueous dispersion into the high-shear rotor-stator mixing environment with additional biochar, additional dispersing agent, an intercalating agent, and/or a neutralizing agent in dependence on the measured concentration or particle size distribution.
16 . The process of claim 1 , further comprising:
prior to subjecting the biochar in the solvent to the high-shear rotor-stator mixing environment, receiving the biochar and the dispersing agent in predetermined proportions;
after subjecting the biochar in the solvent to the high-shear rotor-stator mixing environment to exfoliate graphene oxide:
measuring a concentration or particle size distribution of the graphene oxide in the solvent using at least one inline sensor of the high-shear rotor-stator mixing environment;
adding to the biochar in the solvent one or more of biochar, dispersing agent, an intercalating agent, or a neutralizing agent in dependence on the measured concentration or particle size distribution, and
further subjecting the biochar in the solvent to the high-shear rotor-stator mixing environment to further exfoliate graphene oxide and further measuring the concentration or the particle size distribution until the measured concentration or particle size distribution meets a target range.