Removal methods for sulfur dioxide & hydrogen sulfide

Written by rebecca macken | 13/05/2017
Removal methods for sulfur dioxide & hydrogen sulfide
Sulphur dioxide and hydrogen sulphide are produced under natural and manmade conditions. (Stockbyte/Stockbyte/Getty Images)

Sulphur dioxide and hydrogen sulphide are sulphur-based chemical gases produced both through natural and industrial processes. High levels of both gases are believed to contribute to a variety of health and environmental issues. There are steps you can take to help reduce and remove these gases from the home and the larger environment.

About Sulfur Dioxide

Sulphur dioxide (SO2) is colourless and noxious with a powerful smell and can be present as either a liquid or gas. Created in nature through volcanic activity, it is most often produced through the processing of fossil fuels in industrial and power capacities. The Environmental Protection Agency (EPA) classifies sulphur dioxide as a "highly reactive" gas and has developed industry standards to curb the amount of gas released into the atmosphere. Sulphur dioxide's effects range from the production of acid rain to individual respiratory ailments. However, sulphur dioxide is not all bad; in small levels the chemical is used as a fruit preservative and actually occurs naturally in the body, with the average human body containing an average of 1,000 mg per day. The body is equipped with enzymes capable of breaking down the chemical, but too much of the chemical can still have adverse effects.

About Hydrogen Sulfide

Created through the deterioration of sulphur-comprised proteins, hydrogen sulphide (H2S) is naturally contained in volcanic and natural gases, crude petroleum oil, hot springs, animal and human waste, and as a by-product of sulphur bacteria. Hydrogen sulphide is also produced during industrial processing operations including sewage treatment, food processing and oil refineries. Characterised by its rotten egg-type odour, hydrogen sulphide affects various body systems with low level exposure resulting in short-term respiratory problems, decreased appetite, dizziness, and headaches, and in high concentrations resulting in death.

Removing Sulfur Dioxide with Calcium Oxide

Neutralising through changing the chemical construction of sulphur dioxide is one option for removing the gas from industrial and power facility emissions. Experiments illustrating the effects of combining sulphur dioxide with soda lime, which is comprised of calcium oxide and sodium hydroxide, have been shown to be effective in converting sulphur dioxide into calcium sulphide. The conversion occurs due to the reaction of the sulphur dioxide to the calcium oxide, not only changing the chemical composite, but also reducing the pressure of the gas.

Removing Sulfur Dioxide with Scrubbers

Used in the removal of gas particles from industrial smokestacks, scrubbers work to remove the sulphur dioxide and other gases before they are released into the environment. Non-regenerative and regenerative scrubbers are used to remove sulphur dioxide, with the particles removed by the regenerative scrubber recycled into usable materials. The most common form of scrubber used for sulphur dioxide removal is the non-regenerative wet scrubber, which soaks the flue gases with water slurry and limestone. Like the soda lime combination noted above, this process alters the chemical compound and creates calcium sulphate, also known as gypsum, which is then disposed of or recycled as wallboard or fertiliser. Another scrubber method employs a regenerative scrubber which combines sodium sulphite with the sulphur dioxide which results in sodium bisulfite. The sodium bisulfite is then reduced to sodium sulphite and sulphur using alkali, with the sulphur being used to make sulphuric acid.

Removing Hydrogen Sulfide from Drinking Water

Hydrogen sulphide in drinking water is not an uncommon occurrence and often has no ill health effects, but can affect the taste and smell as well as corrode household items. While water heaters can sometimes be the culprit due to the insertion of a magnesium rod during manufacturing that is meant to protect the heater against deterioration, natural occurrences of sulphur bacteria in water can also be to blame. These bacteria feed on the sulphur in rocks, soil and decomposing plants, and hydrogen sulphide is the by-product. There are three effective methods for removing hydrogen sulphide from drinking water which include chlorination, aeration and carbon filters. Chlorination involves the addition of a small amount of chlorine to the water system which then converts the hydrogen sulphide into yellow sulphur particles which are then filtered out. Aeration involving the addition of compressed air into the water system also results in the conversion of the chemical to yellow sulphur. Carbon filters are most effective with only minor amounts of hydrogen sulphide, as the hydrogen sulphide must be absorbed by the filters.

Removing Hydrogen Sulfide with Pressurized Oxidation

Used in the removal of hydrogen sulphide from well water, pressurised oxidation converts the hydrogen sulphide into water and sulphur through the application of high pressure oxygen. When the oxygen comes into contact with the hydrogen sulphide in the water, the oxygen creates a chemical reaction which results in the breakdown of the hydrogen sulphide into hydrogen and sulphur, with the hydrogen combing with the oxygen to create water. An inductor pumps the oxygen into the well water and as the reaction takes place, the remaining sulphur will shift to the bottom of the well tank.

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