Study On Photosensitized Degradation Of β-Blocker Drugs In Aqueous Fulvic Acid Solutions

It’s well known that with the increasing consumption of β-blocker drugs, the waterpollution resulted from β-blocker drugs was increasingly urgent. Fulvic acid is amulti-functional group ploymers presented in the environment naturally, which has theabilty to absorb spectrum and produce reactive oxidizing substances （ROS）, The ROS cancontribute to the degeadation of organic pollutants degradated in the natural environmentslowly. The aim of the paper which supported by Natural Science Foundation of HubeiProvince was to study the effect and mechanism of fulvic acid photosensitizeing β-blockerdrugs. Besides, structures of different molecular weight and its degradation of propranololwere investigated by exposing the samples to the simulated sunlight. The main contentreaearched and results obtained were as following:In the simulated sunlight, the relationship between fulvic acid and atenolol （AT） andmetoprolol （MT） were studied, besides, the impact of the initial concentration of atenololand metoprolol, pH value, fulvic acid concerntion and metal ion concentrations on thephotosensitization of atenolol and metoprolol were investigated. Results suggested:（1）with the initial concentration of atenolol and metoprolol increasing from2μM to80μM,the reaction rate constants decreased form0.2029min^-1and0.0959min^-1to0.0118min^-1and0.0048min^-1.（2） the photodegradation of atenolol and metoprolol increased withincreasing pH in the alkaline solutions ranging from6¹0, which corresponded toincrease of the fractions of deprotonated forms of the substrates.（3） the photosensitizeddegradation of atenolol and metoprolol increased with increasing concentration of FA at0²4mg/L, until it reached almost a plateau at24mg/L.（4） the inhibition effect wasassociated with the paramagnetic property of the metal ions, four kinds of diamagneticproperty metal ions: Mg²⁺, Ca²⁺, Zn²⁺and Al³⁺showed negligible effect on thephotodegradation of β-blockers, the inhibition of photodegradation increased in the orderof Cr³⁺<Fe³⁺<Cu²⁺<Mn²⁺in deoxygenated FA solutions, which was in good agreementwith the increase of log K of these metal ions.Mechanism betwween fulvic acid and atenolol and metoprolol photo-sensitizeddegradation was investaged by virious quenching reactions, and it was determined by LC- MS product detection. The result displayed that triplet3FA*was considered to be the minereason for the degradation of atenolol and metoprolol （5μM）, which explored under thesunlight of filtered xenon lamp. The occurrence of the degradation of of atenolol andmetoprolol depended on a non-bonding electron transferring from the N atoms of atenololand metoprolol to triplet³FA^*The chemical composition and structure of five fulvic acid fractions wereinvestigeted by term of elemental analysis, UV-visible spectroscopy （UV-Vis）, fouriertransform infrared spectroscopy （FT-IR） and three-dimensional excited/emission matrix（3DEEM） fluorescence spectroscopy. Besides, the photodegradation of propranolol wasdiscussed in the role of different fulvic acids fraction. The studies illustrated that:（1） thelower molecular weight fractions possesss more aromatic C=C content, oxygen-containingfunctional groups and fluorescent chromophores;（2） with the increasing of molecularweight, the aromaticity of fractions diminished, the content of oxygen-containingfunctional groups and fluorescent chromophore gradually reduced, fatty carbon structuregrowed;（3） each fulvic acid fractions has the ability to produce³FA^*under the exposureof sumilated sunlight and UF3has the largest quenching constant because of the morearomaticity and oxygen content;（4） fulvic acid fractions possessing more oxygen contentand fluorescent chromophore exert great influence on the fate of β-blocker pollutants innatural waters.