Provided herein are methods and systems to form calcium carbonate comprising vaterite, comprising dissolving limestone in an aqueous base solution under one or more precipitation conditions to produce a precipitation material comprising calcium carbonate and a supernatant solution, wherein the calcium carbonate comprises vaterite.

The present invention aims to provide techniques for efficiently synthesizing inorganic microparticles. According to the present invention, inorganic carbonate microparticles can be synthesized by generating ultrafine bubbles containing carbonic acid gas by injecting a gas containing carbonic acid gas and a liquid into a reaction vessel through a nozzle to deposit an inorganic carbonate having an average primary particle size of 300 nm or less in the presence of the ultrafine bubbles.

The present invention provides a new method for fixing carbon dioxide. The method for fixing carbon dioxide of the present invention, includes: a contact step of bringing a mixed liquid containing sodium hydroxide and further containing at least one of a chloride of a Group 2 element or a chloride of a divalent metal element into contact with a gas containing carbon dioxide, wherein in the contact step, the mixed liquid and the gas are brought into contact with each other by feeding the gas into the mixed liquid, a concentration of the sodium hydroxide in the mixed liquid is 0.01 N or more and 0.2 N or less, and in the contact step, the feeding is performed by a motor-driven pump, and the motor is driven by utilizing power generated by photovoltaic power generation.

Aspects of the invention include methods of removing carbon dioxide (CO.sub.2) from a CO.sub.2 containing gas. In some instances, the methods include contacting CO.sub.2 containing gas with a bicarbonate buffered aqueous medium under conditions sufficient to produce a bicarbonate rich product. Where desired, the resultant bicarbonate rich product or a component thereof may then be stored or further processed, e.g., combined with a divalent alkaline earth metal cation, under conditions sufficient to produce a solid carbonate composition. Aspects of the invention further include systems for practicing the methods, as well as products produced by the methods.

Disclosed herein is an improved method of brine water treatment including the removal of calcium and/or magnesium-based hardness utilizing CO.sub.2 mineralization resulting in permanent sequestration of the CO.sub.2 via stable precipitates in conjunction with hydrogen and chlorine production from the electrolysis of brine water.

A method including reacting, at a jobsite, a total dissolved solids (TDS) water with a gas comprising carbon dioxide (CO.sub.2) in the presence of a proton-removing agent to produce a CO.sub.2-reduced gas and an aqueous product comprising water and a precipitate, wherein the TDS water comprises produced water, wherein the precipitate comprises one or more carbonates, and wherein the CO.sub.2-reduced gas comprises less CO.sub.2 than the gas comprising CO.sub.2; and separating at least a portion of the water from the aqueous product to provide a concentrated slurry of the precipitate and a TDS-reduced water, wherein the TDS-reduced water comprises less TDS than the TDS water.

Provided is a medical calcium carbonate composition that highly satisfies 1) tissue affinity, 2) in vivo resorbability, 3) reactivity, and 4) mechanical strength required for medical materials to be implanted in vivo, a medical calcium phosphate composition, a medical carbonate apatite composition, a medical calcium hydroxide porous structure, a medical calcium sulfate setting granules, and a bone defect regeneration kit related to the medical calcium carbonate composition, and methods for producing these. The medical composition calcium carbonate that highly satisfies the above described elements, and related medical compositions can be produced by controlling the polymorph or structure of calcium carbonate.

In this disclosure, a process of recycling acid, base and the salt reagents required in the Li recovery process is introduced. A membrane electrolysis cell which incorporates an oxygen depolarized cathode is implemented to generate the required chemicals onsite. The system can utilize a portion of the salar brine or other lithium-containing brine or solid waste to generate hydrochloric or sulfuric acid, sodium hydroxide and carbonate salts. Simultaneous generation of acid and base allows for taking advantage of both chemicals during the conventional Li recovery from brines and mineral rocks. The desalinated water can also be used for the washing steps on the recovery process or returned into the evaporation ponds. The method also can be used for the direct conversion of lithium salts to the high value LiOH product. The method does not produce any solid effluent which makes it easy-to-adopt for use in existing industrial Li recovery plants.

A method of increasing the strength of a carbonate rock is described. The carbonate rock may be located within a subterranean carbonate formation or may be located on a building exterior. The method involves contacting the carbonate rock with a composition comprising a zinc salt or a silicon alkoxide. This may increase the hardness of the carbonate rock by 10% or more.

A method of treating a sulphate-bearing stream which includes the steps of hydrolysing aluminium sulphate to produce a chemically-reactive aluminium trihydroxide and sulphuric acid, adding lime to immobilize the sulphuric acid as gypsum and using the aluminium trihydroxide to remove sulphate from the sulphate-bearing stream without interference of sulphate derived from the aluminium sulphate used as an aluminium source in the hydrolysis step.