Joule Heating Enabled Peroxymonosulfate Thermal Activation For The Degradation Of Carbamazepine

The presence of medicines and personal care products（PPCPs）in the environment can pose a serious threat to biological and human health.Most PPCPs are toxic,stable and difficult to degrade,and traditional wastewater treatment technology is difficult to degrade and remove such organic pollutants.Based on the sulfate radicals（SO₄˙￣,SR）of advanced oxidation process（SR-AOPs）is considered to be one of the most ideal technology PPCPs pollutant removal.SR-AOPs can degrade pollutants by activating persulfate（PS）to produce reactive species.The method of thermal activation of PS has the advantages of simple operation,clean,without adding any chemicals,etc.Joule heat effect is a phenomenon in which part of the electric energy is converted into heat energy when the current flows through the resistance,resulting in a rise in temperature.There are few studies on activation of PS by Joule heating.Graphite felt（GF）is an ideal material for Joule heating because of its excellent conductivity and catalytic properties of persulfate.In this paper,we activated persulfate to degrade carbamazepine（CBZ）by GF-mediated Joule heating system,and analyzed the activation mechanism of the system.The main research contents and conclusions are as follows:（1）Joule thermal properties of common conductive materials were tested.Compared with carbon cloth（CC）,graphite plate（GP）and conductive sponge（CS）,GF had superior electrothermal performance,and the Joule heat generated by GF was positively correlated with input voltage and material thickness.GF-mediated Joule heating system had excellent heating effect on water.The temperature of water was positively correlated with the input voltage and material thickness,and negatively correlated with the volume of heated water.（2）The activation properties of GF-6 on peroxymonosulfate（PMS）and peroxydisulfate（PDS）and the degradation effect of CBZ at 5 V applied voltage were tested.The removal efficiency of CBZ in GF-6/5 V/PMS system is higher than that in GF-6/5 V/PDS system.In this system,the degradation efficiency of CBZ reached 97.5%and the decomposition rate of PMS reached 82.6%within 30 min.With the increase of PMS concentration from 0.25 m M to0.50 m M,the degradation efficiency of CBZ increased from 89.6%in 60 min to 97.5%in 30min.However,the degradation kinetics of CBZ was only slightly accelerated with further increase of PMS concentration.The GF-6/5 V/PMS system had wide p H applicability for the degradation of CBZ.The initial p H(p H_ini)of the reaction solution increased from 3.0 to 9.0,and the degradation efficiency of CBZ decreased only slightly.Common inorganic anions in natural water bodies（Cl￣、NO₃￣、H₂PO₄￣and HCO₃￣）and humic acid（HA）on the degradation of GF-6/5 V/PMS system efficiency had certain inhibitory effect,in which HCO₃￣inhibitory effect of system was most significant,after joining the 5.0 m M HCO₃￣,the degradation rate of CBZ decreased to 38.7%.The removal rate of CBZ by GF-6/5 V/PMS system in tap water and Li lake water were 54.6%and 60.7%,respectively.After ten cycling experiments,the degradation efficiency of CBZ in the system only decreased from 100%to 98.9%.（3）The activation mechanism of PMS in GF-6/5 V/PMS system was analyzed by radical quenching experiment and electron paramagnetic resonance spectroscopy（EPR）.Found by experiments,the PMS by thermal activation,GF-6 catalytic activation and direct reaction with electronic three pathways were activated to produce·OH,SO₄˙￣,O₂˙￣and ¹O₂.When the temperature of the aqueous solution exceeds 50 ^oC,the energy provided by the system is enough to break the O-O chemical bond of PMS and produce·OH and SO₄˙￣,the high temperature environment provided by joule heating can improve the catalytic activation activity of GF and promote the formation of ¹O₂.·OH,SO₄˙￣,O₂˙￣and ¹O₂ participated in the degradation of CBZ,among them,¹O₂ on the degradation of CBZ played the most critical role.A total of seven intermediates of CBZ degradation were detected by liquid chromatography-mass spectrometry（LC-MS）,suggesting that there may be three degradation paths of CBZ.