Recovery and purification of acetic acid from extremely diluted solutions using a mixed bed ion exchange resin -...

A downstream process for the recovery and purification of acetic acid (AA) from an extremely diluted solution (100 mg L^-1) also containing a mixture of contaminating inorganic salts in the form of bicarbonates, phosphates, sulfates and chlorides (DPM medium) has been developed, showing its technical feasibility. The process involves two successive steps based on the use of a mixed bed ion exchange (IEX) resin. The first step, a demineralization treatment to remove the inorganic anions that could potentially interfere with the recovery and purification of AA, involves a combined treatment of calcium precipitation, acidification with the Amberlite IR-120 resin and treatment with the Amberlite MB20 mixed bed resin. This treatment allows the total removal of phosphate and sulfate (and likely bicarbonate) and 90% removal of chloride, while still retaining 91% of AA in solution. In the second step the demineralized medium is treated again with the Amberlite MB20 mixed bed resin in batch to completely remove AA and chloride remaining in solution and, finally, the anion-loaded resin is step-eluted with a low volume of diluted H₂SO₄ to selectively elute AA, obtaining a purified (68.5-82.2% recovery yield and 96.9-99.2% purity) and concentrated (>1500 mg L^-1) solution of the acid.