Construction Of Ethanol-salt Aqueous Two-phase System And Its Application On The Extraction Of Spiramycin

During the preparation of isovalerylspiramycin,large amount of wastewater containing spiramycin is produced.If the wastewater is directly discharged,it will lead to disordered spread of antibiotics and serious environmental pollution.Spiramycin is an antibiotic with excellent antibacterial properties and it can also be used for the synthesis of acetylspiramycin.It will cause the waste of resources if the wastewater is disposed by emisson or biodegradation.So it is of great environmental significance and economic value to recover spiramycin from the wastewater.In this paper,a method for the separation of spiramycin using ethanol-salt aqueous two-phase extraction was established.The influencing factors of extraction and recovery of phase-forming materials were investigated.The aqueous two-phase extraction method is easy to separate spiramycin from extraction solution without back-extraction,and ethanol and salt can be recycled.This method can not only solve the problem of environmental pollution caused by antibiotics,but also can recover spiramycin.The main research and conclusions of this paper are as follows.(1)The ability of twenty-four salts to form aqueous two-phase system with ethanol was investigated.The bimodal data at 25 ? of ten systems that can form aqueous two-phase system with ethanol were measured and fitted.According to the theory of effective excluded volume,the salting out ability of salts,anions and cations was compared.(2)The separation characteristics of the extraction of spiramycin by ethanol-K2HPO4 aqueous two-phase system were investigated and the thermodynamic data of the extraction process were calculated.By studying the influence of operating parameters on the partition coefficient and extraction efficiency,the optimized extraction operating conditions were determined.The optimal operating conditions were K2HPO4 mass fraction of 20%,ethanol mass fraction of 16%,extraction temperature of 25 ?,and system pH of 9.2?9.5.Under the conditions,the partition coefficient and extraction efficiency were over 36.66 and 97.11%,respectively.The results of ?G<0,?H>0,and AS>0 indicate that the extraction process is spontaneous,endothermic and entropy increasing.Spiramycin preferentially distributes into the alcohol-rich phase.(3)The recovery of K2HPO4 in two phases and the stability of spiramycin in alcohol-rich phase were studied.The optimal operating condition for the recovery of K2HPO4 in the lower phase is to adjust pH = 4.0 and add one-fifth lower phase volume of ethanol.The recovery of K2HPO4 reached 97.39%.In the upper phase,the recovery of K2HPO4 was over 74.08%when pH at 5.0?6.0.The remaining K2HPO4 can be further recovered when ethanol is distilled.Spiramycin can stably exist for a long time without degradation in the alcohol-rich phase at 25? with pH of 4.0?10.0,and at 50? with pH of 4.0?5.0.The partition coefficient and extraction efficiency of spiramycin were high using ethanol-K2HPO4 aqueous two-phase extraction,and spiramycin can be recovered by adjusting the pH.The phase-forming materials ethanol and K2HPO4 can be reused by distillation and crystallization,respectively.This method can avoid secondary pollution and reduce raw materials cost.A new method is provided for the treatment of isovalerylmycin production wastewater containing spiramycin.