Kinetics And Mechanisms On The Removal Of Carbamazepine From Aqueous Solution By Hydraulic-Driven Piezo-Activation Of Peroxymonosulfate

Carbamazepine（CBZ）is widely used for the treatment of epilepsy.The parent compounds and some metabolites of CBZ are recalcitrant to biodegradation.They have been detected in both influent and effluent samples from numerous wastewater treatment plants.The bioaccumulation of CBZ presents a challenge to the aquatic ecological environment and human health.Electrochemical activated peroxymonosulfate（E-PMS）process can produce strong oxidizing hydroxyl radicals（^·OH）and sulfate radicals(SO₄^·-),which can effectively remove refractory organic pollutants.However,the requirement of an external direct current power supply will surely increase the difficulty of management and energy cost.Thus,it is infusive to develop an alternative method depending on electrochemical activation of PMS with lower equipment dependence and better energy efficiency.Piezo-catalysis can convert external mechanical energy into electrical energy and form a built-in electric field.Then,a series of redox reactions occur on the surface of the piezoelectric materials.The generated active species can be directly applied to degrade organic pollutants.Hydraulic energy,as a clean and renewable energy resource,is available in the current water treatment or delivery process.The hydraulic-driven piezo-catalysis technology has attracted considerable attention in organic pollutions removal in the remediation of the water environment due to the potential utilization of residual mechanical energy in the environment.Motivated by these,CBZ was used as the target pollutant,and the conventional piezoelectric material barium titanate（Ba Ti O₃,BT）prepared by the hydrothermal method was combined with PMS（BT-PMS）to remove CBZ by harvesting hydro-energy.The feasibility and the effects of operating parameters（especially hydraulic gradient）of the BT-PMS process were investigated.Besides,the hydraulic BT-PMS process was limited due to low degradation efficiency.Although carbon nanotubes（CNTs）can activate PMS more effectively,poor recyclability is a major problem.Hence,CNTs/BT nanocomposite was fabricated and expected to activate PMS more effectively with the stable property in the hydraulic CNTs/BT-PMS process.In order to get further insights into the CBZ removal in the BT-PMS and CNTs/BT-PMS processes,the mechanisms were explored by radical-trapping experiment,calculation of radical steady-state concentrations,estimation of the relative contribution of radicals,and analysis of the intermediate products.In addition,the reason for the high durability of the CNTs/BT composites was investigated.Finally,the application potential of the BT-PMS and CNTs/BT-PMS processes were compared by the experiments of multiple organic decompositions,the effect of actual water matrixes,stability evaluation,and energy consumption.The major conclusions of the article are as follows:（1）The BT prepared by hydrothermal method displayed spherical and smooth morphology with a diameter around 100 nm.The tetragonal phase was dominant in the BT with piezoelectric nature.The piezoelectric constants(d₃₃)of BT was 35.56 pm V^-1.Besides,grape-like CNTs/BT nanocomposites with Ti-C bond were prepared.By comparison,the CNTs/BT composites had better piezoelectric(d₃₃ was 48.45 pm V^-1)and electrochemical properties.（2）The removal ratio of CBZ in the BT-PMS process attainted 76.17%within 180 min.In addition,the mineralization ratio in the BT-PMS process（44.10%）was much higher than that of BT and PMS processes within 15 h.The degradation of CBZ satisfied the pseudo-first-order kinetics.The rate constants（k）of the BT-PMS process was 8.15×10^-3 min^-1,and a significant synergetic effect between BT and PMS was observed with a prodigious synergistic index（14.90）.In contrast to the BT-PMS process,the removal ratio of CBZ in the CNTs/BT-PMS process was markedly higher,which attainted 91.93%within 120 min.And the mineralization ratio after 10 h in the CNTs/BT-PMS process（59.68%）was also much higher than that of the BT-PMS process.The degradation of CBZ satisfied the pseudo-first-order kinetics.The k value of the CNTs/BT-PMS process was 20.71×10^-3 min^-1.Besides,the durability of the composite was relatively high.It could maintain the oxidizing capacity for the sequential degradation test,and 77.74%of CBZ was removed at the fifth run in the CNTs/BT-PMS process.（3）Hydraulic gradient is an important factor in the hydraulic-driven piezo-activation of the PMS process.A positive correlation between piezo-potential/current and hydraulic gradient value was found in both BT-PMS and CNTs/BT-PMS processes.However,there was an optimal G value(7.72 s^-1)for CBZ removal in the above processes.Besides,the more CNTs were loaded,the better treatment performance in the CNTs/BT-PMS process.The treatment efficiency of CBZ increased with increasing the PMS concentration or catalyst dosage,within a given range.In addition,the treatment efficiency of CBZ decreased with decreasing the CBZ concentration in the above processes.The wide range of initial p H for adaption was a characteristic of the BT-PMS and CNTs/BT-PMS processes.（4）The e^-,h⁺,superoxide radical（^·O₂^-）,^·OH,SO₄^·-,and singlet oxygen（¹O₂）were present in both BT-PMS and CNTs/BT-PMS processes.Among them,^·OH was dominating reactive oxygen species（ROS）for CBZ degradation in the above processes.The relative contribution of^·OH was 65.40%and 85.59%,respectively.The improvement of piezoelectric properties and electrochemical performance of CNTs/BT promoted the separation of hole-electron during piezo-catalysis.Thus,the CNTs/BT-PMS process could generate more active species than the individual CNTs-PMS and BT-PMS processes.Which made the CNTs/BT-PMS process have stronger oxidative degradation ability.In addition,the fluid-induced piezoelectric field could replenish more electrons lost in the CNTs during the reaction,thus reducing the destruction of CNTs caused by chemical oxidation in the CNTs/BT-PMS process.（5）Various refractory pollutants（e.g.,nitrobenzene,phenol,benzoic acid,and diclofenac）could be effectively removed in both BT-PMS and CNTs/BT-PMS processes.The Cl^-significantly promoted the degradation of CBZ.However,PO₄^3-,HCO₃^-,and humic acid exhibited inhibition for the degradation of CBZ.The BT and CNTs/BT maintained high reactivity and robust perovskite structure without phase transition after10 cyclic tests.Besides,the valence state of transition metal had not changed before and after 10 cyclic tests.Compared with the BT-PMS process,the CNTs/BT-PMS process showed better removal performance for various refractory organic pollutants,stronger resistance to ion shock,and better adaptability to actual water bodies.Importantly,the energy consumption of the hydraulic CNTs/BT-PMS process was 449.86 k Wh m^-3order^-1.The energy consumption of CNTs/BT-PMS process induced by nano piezoelectric energy without direct current was only 26.59%and 24.00%of the BT-PMS and the traditional E-PMS induced by direct current,respectively.Thus,the CNTs/BT-PMS process might be an efficient,sustainable,and energy-saving process for water treatment by the potential utilization of residual hydro-energy in water transportation.