Research On Pretreatment Of P-toluene Sulfonic Acid Wastewater

P-toluene sulfonic acid, which is the main component of doxycyclin dewatering mother liquor, has strong biological toxicity and inhibitory effect, and that is the main reason why doxycyclin dewatering mother liquor was difficult to treat with biological treatment. Based on the researches of p-toluene sulfonic acid simulated wastewater being treated with alkaline hydrolysis and Fenton oxidation process, the effects of dewatering mother liquor which was pretreated by the process of calcium salt precipitation-alkaline hydrolyzing and calcium salt precipitation-alkaline hydrolyzing-Fenton oxidation were emphatically studied. and the mechanisms of p-toluene sulfonic acid simulated wastewater being pretreated with alkaline hydrolyzing and Fenton oxidation process were discussed.The result showed that both alkaline hydrolysis and Fenton oxidation process showed good removal efficiencies for p-toluene sulfonic acid simulated wastewater, sulfonic acid group fell off and transformed to SO42- after Fenton oxidation, whereas didn't fall off after alkaline hydrolyzing. For the raw simulation wastewater whose COD was 924 mg/L and BOD5/COD was 0, when being alkaline hydrolyzing for 4h, the COD in the effluent was 963 mg/L, BOD5/COD is 0.61; while after being axidated by Fenton reagent, p-toluene sulfonic acid removal rate was 98%, COD removal was 85%, BOD5/COD was rised to 0.5.Calcium salt precipitation-alkaline hydrolyzing process was proved to be an effective pretreatment process for doxycyclin dewatering mother liquor. With the influent F" 13160 mg/L,COD 112425 mg/L,BOD5/COD 0.074, the effluent F- could be reduced to 140 mg/L by calcium salt precipitation when dosage of Ca (OH)2 was 150% and reaction time was 40 min. After being pretreated by calcium salt precipitation-alkaline hydrolyzing, the effluent COD was 104000 mg/L,BOD5/COD was 0.6, then COD could be reduced to 60 mg/L again in the following biological treatment. After being pretreated by calcium salt precipitation-alkaline hydrolyzing-Fenton oxidation, the effluent COD was 104000 mg/L, but BOD5/COD was decreased from 0.6 to 0.48, What's more, COD was reduced just to 200 mg/L with the following biological treatment, which was significantly higher than the former pretreatment.Hydrolysis product of P-toluene sulfonic acid under the alkaline condition was proved to be hydroxyl benzene sulfonic acid. The oxidation mechanism was devided into two stages, with the small dosage of H2O2, it generates benzene quinone,hydroquinone,formic acid,acetic acid and other intermediate products, these intermediate products complexed with ferric salt and hinded further reaction. When dosage of H2O2 was increased to a certain value, the reaction rate was accelerated and those intermediates generated in the first stage were degradated for water and carbon dioxide.