AOX Reduction Through Increased Oxidation Potential in the First Caustic Extraction Stage, 1991 Pulping Conference Proceedings

The reduction of AOX in the effluent from the caustic extraction stage has been found to increase as the standard oxidation potential of the reinforcing agent in the first caustic extraction stage increased. A brownstock pulp was chlorinated under uniform conditions to produce a base level of chloro-organic material entering the caustic extraction stage. The chlorinated pulp was treated with a standard caustic extraction (E), an oxygen reinforced caustic extraction (Eo), and a peroxide - oxygen reinforced extraction stage (Eop). The brownstock study obtained up to 30% AOX reduction in the peroxide reinforced extraction stage effluent.

In addition to the brownstock work, a series of tests using oxygen, potassium permanganate, hydrogen peroxide with oxygen, and ozone with oxygen reinforced caustic stages were also run using two different model lignin compounds. In all cases, increasing the oxidation potential of the rein-forcing agent resulted in a reduction of the AOX detected in the effluent.