Treatment Of Endocrine Disruptor Prednisolone By UV/Chlorine Advanced Oxidation Process

Prednisolone?PDNN?was poorly eliminated by the traditional chlorine treatment,and the residual PDNN has potential ecotoxicity to aquatic fauna?fish,daphnia,etc.?,thus,UV/chlorine advanced oxidation technology?UV/Cl?was applied to degraded PDNN.The degradation of PDNN by UV/Cl was comprehensively explored and the study was divided into four sections,including kinetics,environmental factors,degradation mechanism,and toxicity assessment.The results are summarized as follows:?1?For the section of kinetics,the optimum chlorine dose was firstly determined to be 100?M in the UV/Cl process,a low chlorine??100?M?promoted the PDNN degradation,while a high chlorine dosage?>100?M?was adverse.Then UV/Cl was found to be the most efficient method for PDNN degration among UV/Cl,UV/H₂O₂,UV,and chlorine,furthermore,the EE/O_T?The electrical energy required to degrade PDNN by one order magnitude in unit volume of contaminated water?of UV/Cl was lowest among UV/Cl,UV/H₂O₂ and UV,which indicated that UV/Cl was a potential and prospect market application.In the UV/Cl system,free radicals quenched by tBuOH suggested that the PDNN degradation in UV/Cl process was involved in the participation of hydroxyl radical?·OH?and reactive chlorine species?RCS?.Additionally,based on the competitive kinetics experiments,the second-order rate constants of·OH with PDNN was determined to be 1.10×10⁹ M^-1 s^-1 and the relative contribution of·OH and RCS to the degradation of PDNN were calculated to be 17.84%and 6.21%,respectively.?2?The influence of environmental factors including pH,anions?Cl^-,Br^-,HCO₃^-and SO₄2^-?,NH₄⁺and fulvic acid?FA?were invested on the degradation of PDNN.The pH?4.0¹0.0?showed negligible effect,while the investigated anions?Cl^-,Br^-,HCO₃^-and SO₄2^-?,NH₄⁺and FA exerted negative impact on PDNN degradation.An inhibitory effect to PDNN degradation was observed in the synthetic urine by comparing with the other two aqueous circumstances,which showed that the influence of components in urine should be comprehensively considered when urine was used as the aqueous circumstance for residual pharmaceuticals elimination.?3?The possible degradation pathway of PDNN in UV/Cl was proposed based on the frontier orbitals calculation of PDNN from Gaussian and the results of HPLC-ESI-tqMS.The proposed pathway was mainly involving the addition of?,?-unsaturated ketone at C₁ or C₅,the photolysis of C₁₇ and H-abstraction of C₁₁.Moreover,?,?-unsaturated ketone moiety was proved to be the main reactive site of PDNN.The Microtox test of bacterium Vibrio fischeri and Ecological Structure-Activity Relationship Model?ECOSAR?program were employed to evaluate the acute toxicity and chronic toxicity of the degradation process and products of PDNN treated by UV/Cl.The results showed that UV/Cl can effectively and safely degrade PDNN and we can avoid the production of toxic intermediates?TP396?TP396-C₁Cl and TP396-C₅Cl?and TP414-C₁Cl-C₅OH?by strictly controlling the degradation time.