The invention belongs to field of waste water treatment be specifically related to a kind of method for preparing L (+)-23 dihydroxybutanedioic acid that reclaims from the L-methyldopa factory effluent.In the L-methyldopa factory effluent add the inorganic acid salt of calcium to react obtain L (+)-2 the precipitation of 3-dyhydrobutanedioic acid calcium (II) precipitation is used aqueous suspension then with the mineral acid effect obtain L (+)-2 the aqueous solution of 3-dyhydrobutanedioic acid (I) then through decolorizing with activated carbon hot filter concentrating under reduced pressure crystallization the centrifugal crude product that makes L (+)-23 dihydroxybutanedioic acid (I) make the elaboration of L (+)-23 dihydroxybutanedioic acid (I) after refining.The present invention is simple to operate the reaction conditions gentleness be easy to control products obtained therefrom purity is high and yield is high L (+)-2 in the L-methyldopa factory effluent have been solved thoroughly the pollution of 3-dyhydrobutanedioic acid sodium to environment realized recycling economy reduced production cost process stabilizing be applicable to suitability for industrialized production.

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