In an embodiment a method includes loading an absorbent with a carbon dioxide in a first device, wherein a hydrogen carbonate-containing solution is formed, feeding the hydrogen carbonate-containing solution from the first device into an electrolysis unit, electrolyzing the hydrogen carbonate-containing solution in the electrolysis unit to release carbon dioxide, wherein a carbonate-rich solution is formed in the electrolysis unit, forming oxygen, hydrogen and carbon dioxide in the electrolysis unit, and recycling the carbonate-rich solution from the electrolysis unit to the first device.

Slurries and methods of making slurries for modifying and extending relative humidity control ranges. The slurries may include a saturated aqueous salt and one or more other reagents selected to provide a controlled modifiable narrow range of relative humidity. The saturated aqueous salt may be one or more of sodium chloride, potassium chloride, potassium citrate, sodium formate, and/or magnesium chloride, and the one or more other reagents may be one or more of a lactate salt, glycerol, and/or an acetate salt, for example.

A treatment composition includes a scavenger, an amine, and optionally a booster amine. A treatment composition may be contacted with an H.sub.2S rich stream by direct addition of the composition to the H.sub.2S rich stream, or by bubbling the H.sub.2S rich stream through the composition. The H.sub.2S rich stream may be e.g. a produced gas, a biogas, a crude oil, or a produced water. The treated streams have a reduced amount of H.sub.2S (and/or another sulfhydryl compound) therein, when compared to the amount of H.sub.2S in the stream prior to the treatment. The compositions and methods of treating are characterized by a substantial absence of, or reduction in the amount of precipitate formed thereby, when compared to methods and compositions of the prior art.