Barium-EDTA chelate

Thennodynamic inhibitors are complexing and chelating agents, suitable for specific scales. For example, for scale inhibition of barium sulfate, common chemicals are ethylenediaminetetraacetic acid (EDTA) andnitrilotriacetic acid. The solubility of calcium carbonate can be influenced by varying the pH or the partial pressure of carbon dioxide (CO2). The solubility increases with decreasing pH and increasing partial pressure of CO2, and it decreases with temperature. 

Acid cleaning agents such as hydrochloric, phosphoric, or citric acids effectively remove common scaling compounds. With cellulose acetate membranes the pH of the solution should not go below 2.0 or else hydrolysis of the membrane will occur. Oxalic acid is particularly effective for removing iron deposits. Acids such as citric acid are not very effective with calcium, magnesium, or barium sulfate scale in this case a chelatant such as ethylene diamine tetraacetic acid (EDTA) may be used. 

Ba 2.2.2 )2 is more stable than the barium chelates of the polyanionic ligands EDTA and EGTA (85). 

Other scales, such as calcium sulfate (CaSO and barium sulfate (BaSO ) are only slightly soluble in acid. Both are soluble in complexing agents such as EDTA and other carboxylic acid-type chelating agents. Barite can be very hard and thus chemically impenetrable, or it can be fine and soft, thereby enabling mechanical removal or partial chemical removal. Barite sometimes occurs in mixed-scale deposits, wherein an acid-soluble portion (e.g., calcium carbonate) can be removed, along with subsequent physical removal of the barite portion. 

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