RECOVERY OF ACIDS FROM STAINLESS WASTE PICKLING SOLUTION WITH COLUMN EXTRACTOR

摘要

PURPOSE: A method of extracting free nitric and hydrogen fluoride from the waste pickling solution of the stainless steel by organic solution containing tributyl phosphate. The free nitric and fluoric acid in the organic solution is later reverse extracted by water to carry on the continuous recovery. The method has high recovery rate of the acid than the conventional stirring-separation method and the treatment volume is increased while the installation area is decreased. The method is a novel economical method of column extraction which recovers the acids from the waste pickling solution, minimizing the discharge of environmental pollutants. CONSTITUTION: The extraction method comprises: a first step of extracting free nitric and hydrogen fluoride in the waste pickling solution of stainless steel with an organic solution containing 60-80 %(v/v) of tributyl phosphate by column extractor wherein the pulse velocity (AxF) is 150-170 cm/min, while the phase equilibrium of the waste acid wash/organic solution (A/O) is 1/3-2/3, total flow rate based on the phase equilibrium (A/O) being 3-4.2 mL/min per cm¬2 and a second step of reverse extracting nitric and fluoric acid from the above organic solution by water, wherein the pulse velocity (AxF) is 140-160 cm/min. while the phase equilibrium of the waste acid wash/organic solution (A/O) is 2/3-2, total flow rate based on the phase equilibrium (A/O) being 1.5-2 mL/min per cm¬2.