Copper Oxides Activated Persulfate For Pharmaceuticals Removal

Persulfate activation technology is an advanced oxidation technology based on sulfate radical(·SO4-).Because of its strong oxidizing ability and wide application range,it has broad application prospects in solving environmental sewage.Efficient and fast activation of persulfate is the focus of persulfate advanced oxidation technology.There are many methods for the activation of persulfate.In contrast,the activation of persulfate with transition metal oxides is easy to operate,consumes less energy,and has obvious advantages.However,the mechanism and key parameter are still unclear.In this work,three different morphologies of CuO catalysts were synthesized by simple hydrothermal method and used to degrade pharmaceuticals.The catalytic reaction mechanism was explored.The main content is summarized as the following three parts:(1)In this chapter,CuO nanoparticles was synthesized by a simple hydrothermal method and investigated as a heterogeneous activator of persulfate for the degradation of cephalexin and ofloxacin.X-ray photoelectron spectroscopy and hydrogen temperature-programmed reduction measurements reveal that CuO contains two types of Cu2+:one has more electron deficiency(named as Cu2+-h)and the other has relatively higher electron density(named as Cu2+-1).Electron paramagnetic resonance and radical scavenger experiments demonstrate that·SO4-and·O2-are responsible for the efficient degradation of cephalexin and ofloxacin,respectively.·SO4-can be produced through the electron transfer from Cu2+-1 to PS and the cleavage of peroxy bond,while·O2-can be produced via the electron transfer from PS to Cu2+-h and the cleavage of S-O bond.Finally,the degradation intermediates were identified by liquid chromatograph-mass spectrometry.This study proposed a novel mechanism for the activation of persulfate with CuO,which is useful for the rational design of persulfate activator for controlling the production of active species.(2)In this paper,CuO nanorods synthesized by a hydrothermal method was used to activate persulfate(PS)for removing ciprofloxacin(CIP)in water.The influences of reaction parameters and coexisting substances on this process were studied.Under the optimal conditions([CuO]O0?6.3 mmol L-1,[PS]0=1 mmol L-1,pH 8),CIP was completely degraded and the total organic carbon removal efficiency was 84.2%.Ca2+,Mg2+and Cl-had little effect on CIP removal,while fulvic acid showed a slight inhibitory effect.By contrast,bicarbonate enhanced CIP degradation and significantly suppressed Cu leaching.Subsequently,the reactive species for CIP degradation were identified by electron paramagnetic resonance and radical scavenging experiments.Although the decomposition efficiency of PS was significantly accelerated by increasing pH,similar amounts of·O2-,·OH,·SO4-and1O2 were detected at different pH,suggesting the formation of more surface activated PS at higher pH.The reactive species for CIP degradation were found to be dependent on solution pH.CIP was mainly degraded by·S04-and1O2 at acidic conditions.The activated PS might have high selectivity towards CIP and its amount might be higher than that of radicals at pH 8.In addition,the uncharged surface of CuO at pH 8 facilitated the adsorption of CIP,which is beneficial to the surface reaction between CIP and activated PS.Hence,the activated PS was the dominated species for CIP degradation at this pH.(3)In this chapter,CuO nanosheets is synthesized by hydrothermal method,which effectively catalyzes the persulfate(PS)for the degradation of sulfamethoxazole(SMX).The amount of catalyst,the amount of PS,the pH,and the effect of coexisting substances in water on the reaction were evaluated.It was found that activated PS and traces·O2-and 1O2 are reactive oxygen species in the CuO activated PS system.Experiments have shown that activated PS dominates,not·O2-and 1O2·Electron paramagnetic resonance(EPR)studies have shown that·O2-and 102 are produced.Combining all the experimental facts,it is proposed that the activated PS is the main active oxygen species produced on the surface of CuO,and the small amount of·O2-and 1O2 produced.Cl-and HCO3-have no effect on SMX degradation in CuO-activated persulfate systems.indicating that the system is expected to be applied to the treatment of actual water bodies.