Methods for scavenging carbon disulfide (CS.sub.2) from hydrocarbon streams using treatment compositions comprising at least one CS.sub.2 scavenger and at least one phase transfer catalyst therein. The CS.sub.2 scavenger may comprise at least one polyamine with the general formula: H.sub.2N(R.sub.1NH).sub.xR.sub.2(NHR.sub.3).sub.yNH.sub.2 wherein R.sub.1, R.sub.2, R.sub.3 may be the same or different H, aryl or C.sub.1-C.sub.4 alkyl; and x and y may be integers from 0 to 10. A hydrocarbon product with a reduced concentration of CS.sub.2 therein.

Provided is a system for purifying biogas. The system for purifying biogas utilizes a separating unit for methane and carbon dioxide that connects to a separating unit for biogas and a separating unit for carbon dioxide to separate methane and carbon dioxide from the biogas. The separating unit for methane and carbon dioxide may separate the methane and the carbon dioxide. The separating unit for carbon dioxide may separate water and the carbon dioxide. The system for purifying biogas provides high concentration methane for use as fuel for motor vehicles and recycle the water to separate biogas repeatedly.

Methods for removing oxyanions from water according to the following steps: (i) dissolving an oxyanion precipitating compound into the aqueous source to result in precipitation of an oxyanion salt of the oxyanion precipitating compound; and (ii) removing the oxyanion salt from the water containing the oxyanion to result in water substantially reduced in concentration of the oxyanion; wherein the oxyanion precipitating compound has the following composition:

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wherein A is a ring-containing moiety and X.sup.m is an anionic species with a magnitude of charge m. The invention employs bis-iminoguanidinium compounds according to Formula (1a) as well as neutral precursor compounds according to Formula (1), which can be used for removing undesirable species from aqueous solutions or air, such as removal of sulfate from water and carbon dioxide from air.

A carbon dioxide absorbent composition is described, including (i) a liquid, nonaqueous silicon-based material, functionalized with one or more groups that either reversibly react with CO.sub.2 or have a high-affinity for CO.sub.2, and (ii) a hydroxy-containing solvent that is capable of dissolving both the silicon-based material and a reaction product of the silicon-based material and CO.sub.2. The absorbent may be utilized in methods to reduce carbon dioxide in an exhaust gas, and finds particular utility in power plants.

Methods of reducing the water content of a wet gas are presented. In one case, the method includes exposing the gas to an amine-terminated branched polymer solvent to remove a substantial portion of the water from the wet gas, exposing the diluted solvent to carbon dioxide to phase separate the solvent from the water, and regenerating the solvent for reuse by desorbing the carbon dioxide by the application of heat. In another case, the method includes exposing the gas to a cloud-point glycol solvent to remove a substantial portion of the water from the wet gas, heating the diluted solvent to above a cloud point temperature for the solvent so as to create a phase separation of the solvent from the water so as to regenerate the solvent for reuse, and directing the regenerated solvent to a new supply of wet gas for water reduction.

Materials, methods of making, and methods of using a stable and regenerable immobilized amine sorbents for rare earth element and heavy metal recovery from liquid sources. Embodiments of the invention relate to the novel combination of different polyamines, primarily polyethylenimine Mw=800 (PEI.sub.800), and an epoxysilane, namely 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane (ECTMS), covalently immobilizing the REE and heavy metal-adsorbing amine sites within low cost, porous silica particles.

A process to remove H.sub.2S from a stream comprising the steps of adding a dispersion of colloidal nanoparticles having surface functionality comprising Copper, Zinc, Iron, or Manganese, and a triazine. The stream is selected from the group consisting of Oil streams, Gas streams, CO.sub.2 point source purification streams, and Geothermal Energy System streams.

A system and a process for capturing Carbon Dioxide (CO.sub.2) from flue gases are disclosed. The process comprises feeding a flue gas comprising CO.sub.2 to at least one Rotary Packed Bed (RPB) absorber rotating circularly. A solvent may be provided through an inner radius of the RPB absorber. The solvent may move towards an outer radius of the RPB absorber. The solvent may react with the flue gas in a counter-current flow. The process further includes passing the flue gas through at least one of a water wash and an acid wash to remove traces of the solvent present in the flue gas. Finally, the solvent reacted with the CO.sub.2 may be thermally regenerated for re-utilizing the solvent back in the process.

A method and a system for the removal of carbon dioxide from solvents.

A process for removing sulfur dioxide from a feed gas stream, which comprises (i) contacting the feed gas stream with an aqueous lean absorbing medium comprising a chemical solvent comprising a regenerable absorbent, a physical solvent, and one or more heat stable salts. The regenerable absorbent is an amine. The ratio of the wt % of the physical solvent over that of the regenerable absorbent is 0.5 to 2.5. The ratio of the wt % of heat stable salts over that of the regenerable absorbent is 0.29 to 0.37. The pH of the lean absorbing medium is 6 or less. With the process SO2 can be selectively removed. When the absorbing medium is stripped, a reduced amount of energy is required as compared to known processes.