Sodium Hydroxide (NaOH)

Sodium hydroxide is an inorganic compound with the formula NaOH with a molecular weight of 40 grams per mole. It is a white solid ionic compound consisting of sodium cations Na+ and hydroxide anions OH−.  Hepure provides a 25% sodium hydroxide solution in 560 pound drums (55 gallons), 2400 pound totes (275 gallons), and custom mixtures of any percentage.

Sodium hydroxide is usually applied by injection prior to addition of bioremediation or chemical oxidation supplements.  It will diffuse throughout the aquifer to optimize conditions for remediation.  Prior to the field injections, a soil buffering test is performed in the laboratory to determine the amount of sodium hydroxide needed to raise the pH of the soil.  Buffer capacity is the amount of acid or base a buffered solution can soak up before its pH will start to change significantly. The buffer capacity of a soil is important in determining how its pH will change.

 

Soil Remediation:

1. pH Adjustment: Sodium hydroxide can be used to raise the pH of acidic soils. Certain contaminants, like heavy metals, become less soluble and mobile in alkaline conditions, thereby reducing their bioavailability and potential for leaching into groundwater.
2. Enhanced Bioremediation: Some beneficial soil microbes thrive in neutral to slightly alkaline conditions. By adjusting the pH with sodium hydroxide, you may enhance the growth and metabolic activities of these microbes, promoting bioremediation of organic contaminants.
3. Desorption of Contaminants: Sodium hydroxide can facilitate the desorption of some contaminants from soil particles, making them more accessible for removal or degradation.

Water Remediation:

1. pH Adjustment: Similar to its use in soil remediation, sodium hydroxide can be used to raise the pH of acidic wastewater. This is often required for industrial wastewaters that are acidic due to the presence of acidic waste products.
2. Precipitation of Metals: At high pH, many heavy metals form hydroxide precipitates that are insoluble and can be easily removed from water via sedimentation and filtration. This is a common method used in the treatment of industrial wastewater to remove metals.
3. Neutralization of Acidic Wastewater: In industries that produce acidic effluents, sodium hydroxide can be used to neutralize the waste, making it safer for disposal or further treatment.

 

Sodium hydroxide is used in the environmental remediation business to adjust the pH of acidic soils and aquifers prior to remediation.  Many remediation methods such as bioremediation and chemical oxidation can be optimized by adjustment of the pH to a range which is more neutral, 6 to 9.  The oxidant sodium persulfate is more highly reactive when applied when the pH is above 10.5.

Various minerals in soil help to buffer against changes in pH when an acid or base is added. At high pH, calcium, magnesium and potassium oxides, together with carbonates, help to buffer pH changes; at acidic pH, aluminum oxides and iron hydroxides act as buffering agents; at intermediate pH levels, soil organic matter, mineral weathering and exchange reactions help to buffer the soil.

A higher buffer capacity means that the soil can absorb more acid and/or base without a significant change in PH. In general, clay soils have higher buffer capacity than sandy soils, and a higher organic matter content tends to increase buffering capacity.

John Brennan  https://www.hunker.com/12450132/buffering-capacity-of-soils

Cronk, G., Koenigsberg, S., and Schlott, D. Controlled Vadose Zone Saturation and Remediation (CVSR) Using Chemical Oxidation. Presentation at the Battelle 7th International Conference on Remediation of Chlorinated and Recalcitrant Compounds, May 24-27, 2010