H2S scavenger can be used specifically for brine-base fluid systems to remove H2S. Recommended treatment levels are 1 gal/100 bbl (0.29 kg/m3). Use higher concentrations where higher levels of H2S exist in the mud to be treated. Under optimal conditions, each pound per barrel (2.85 kg/m3) of H2S scavenger can consume 800 mg/L of dissolved H2S. H2S scavenger has been used successfully to treat water-base fluids where zinc cannot be used for environmental reasons. Another popular treatment for H2S is to rely on high pH to neutralize the acidic hydrogen sulfide (also known as hydro sulfuric acid) and render it non-volatile.
H2S + OH– -» H2O + HS–
This can be done in a completely solids-free way, and any base can do it; however, treatment with base raises the pH of the fluid. Getting enough sodium hydroxide in solution to provide a large capacity for scrubbing requires a very high pH, approximately 12 to 13. Lime is somewhat better in this regard because it has limited solubility at high pH. This allows additional capacity to scrub H2S to be built up in the system in the form of undissolved lime. Organic amines, such as ethanolamine, can also provide a high pH sink for H2S, while buffering the pH around 10.