Efficiency And Mechanism Of Naproxen Degradation In Cu~0/Peroxymonosulfate System Enhanced By Reducting And Complexing Reagents

Naproxen(NPX)is the most commonly detected pharmaceutical and personal care products(PPCPs)worldwide in aqueous environment,which had negative impact to human health and eco-environment.And they were released to the aqueous environment for the poor biodegradation efficiency in wastewater treatment processes.Thus,it is necessary to use advanced oxidation processes to degrade it efficiently.Peroxymonosulfate(PMS)based technologies has been regarded as a promising technology for it can be activated to generate selective reactive species.Zero-valent copper(ZVC)activation is an alternative PMS activation method,for its higher stability in air,more easy-storing and stronger electron transfer efficiency than zero-valent iron.Based on the activation of PMS by ZVC,the most appropriate ZVC materials for the activation of PMS to degrade naproxen were confirmed.Additionally,reductive and complixative enhancement on the degradation of naproxen in ZVC activated PMS system were proposed.Based on this,the mechanism of synergistic enhancement was investigated to alleviate the intrinsic drawbacks in ZVC activated PMS systems(the easily oxidation of Cu+ in solution).Firstly,based on ZVC/PMS system,different ZVC materials were selected,with ZVC activated PMS system conducted and the degradation of naproxen is studied.Copper sheet(CS),graphene-coated copper sheet(GCS),copper foam(CF)and graphene-coated copper foam(GCF)were selected to investigate the influences of initial p H,catalysts dosage and PMS concentrations on naproxen degradation.Additionally,the reactive species generated in ZVC/PMS systems and the degradation products of naproxen were identified.The comparison on the degradation of naproxen in the selected ZVC materials and copper powder activated PMS systems was also discussed.Results showed that the size of ZVC materials is the key to the degradation efficiencies of NPX in ZVC/PMS systems.The degradation efficiencies of NPX were 33.1% and 85.2% in CS/PMS and CF/PMS system.Additionally,graphene coating on ZVC make a 30% decrease on copper release in ZVC/PMS system.The reactive species were identified to be hydroxyl radicals,and PMS act as an electron acceptor,copper act as electron donor and transferring body,while water molecule is the source of hydroxyl radicals.The graphene coating can inhibit the release of copper ion.Cu~0/PMS showed best degradation efficiency in naproxen degradation.The degradation efficiency of naproxen reached 100% in 10 min in Cu~0/PMS system.However,solution p H and Cu~0 dosage showed a significant effect on naproxen degradation in Cu~0/PMS system.Cu~0 is the most appropriate ZVC materials for the activation of PMS to degrade naproxen by comparison with CS,GCS,CF and GCF.Secondly,reductants enhanced the degradation of naproxen in Cu~0/PMS system to alleviate the intrinsic drawbacks(the easily oxidation of Cu+ in solution).The comparison of different reductants effects on naproxen degradation in Cu~0/PMS system were carried out and Hydroxylamine(HA)was the best.Then,the influences of initial p H,Cu~0,hydroxylamine and PMS concentrations on naproxen degradation were investigated.Atonally,the mechanisms of hydroxylamine enhancement were studied.Results showed that hydroxylamine can significantly enhance the degradation efficiency of naproxen in Cu~0/PMS system as well as extending the p H range.The degradation efficiency of naproxen in Cu~0/PMS system increased from 16.4% to 96.7% in 6 min with the addition of hydroxylamine,with the degradation rate increased by 17 times.Cu~0/HA/PMS system exhibit good degradation efficiency on naproxen in the p H range from 3.0 to 7.0,with a degradation of above 95% in all cases.The reactive species of Cu~0/HA/PMS system were proved to be hydroxyl radicals and sulfate radicals.Hydroxylamine can enhance the PMS activation efficiency by reducing Cu2+ and accelerating the corrosion of Cu~0.The degradation intermediates were detected as well as the degradation by-products of hydroxylamine were analyzed to be the environmentally friendly gas N2.Thirdly,it was proposed that complexants enhanced the degradation of naproxen in Cu~0/PMS system to alleviate the same intrinsic drawbacks.The comparison of different complexants effects on naproxen degradation in Cu~0/PMS system were carried out and Neocuproine(NCP)was the best.Then,the influences of initial p H,Cu~0 and neocuproine concentrations on naproxen degradation were investigated.Additionally,the mechanisms of neocuproine enhancement were studied.Results showed that neocuproine can enhance the degradation of naproxen in Cu~0/PMS system.The degradation efficiency of naproxen in Cu~0/PMS system increased from 51.3% to 90.6% in 15 min with the addition of neocuproine,with the degradation rate increased by 2 to 8 times.However,the addition of neocuproine could not extend the p H range of Cu~0/PMS system.neocuproine can enhance the degradation of naproxen in Cu~0/PMS system by the complexing effect of Cu(I)-NCP,which can avoid the oxidation of Cu+.The reactive species were proved to be Cu(III)-NCP.Finally,the synergistic enhancement of neocuproine and hydroxylamine on naproxen degradation in Cu~0/PMS system were investigated.The influences of initial p H,Cu~0,neocuproine,hydroxylamine,PMS and naproxen concentrations on naproxen degradation were investigated.Synergistic mechanisms of neocuproine and hydroxylamine were discussed.Results showed that neocuproine and hydroxylamine can synergistically enhance the degradation of naproxen in Cu~0/PMS system.The degradation efficiency of naproxen in Cu~0/PMS system increased from 16.32% to 98.57% in 6 min with the addition of neocuproine and hydroxylamine.Cu~0/NCP/HA/PMS showed best naproxen degradation performance in the p H range from 4.0 to 6.0,which showed more than 95% degradation efficiency of naproxen in 6 min in all cases.Cu(III)-NCP were also proved to be the reactive species in Cu~0/NCP/HA/PMS system.The addition of neocuproine can avoid the oxidation of Cu+ released by the corrosion of Cu~0 via the formation of stable Cu(I)-NCP complexes.While the addition of hydroxylamine can enhance the corrosion and reduce Cu(II)to enhance the concentration of Cu(I)-NCP,leading an enhancement of PMS activation and the degradation of naproxen in Cu~0/PMS system.