Study On Catalytic Degradation Of Phenolic Pollutants In Water By Two Typical Ferroelectric Materials

As one of the difficult-to-degrade organic pollutants in the environment,chlorophenol is an important factor leading to water pollution.Chemical oxidation is an Advanced Oxidation Process（AOPs）in traditional wastewater treatmen which has various disadvantages such as high energy consumption,harsh conditions,etc.Ferroelectric catalysis can use primary energy in the environment applying to the oxidation degradation of organic sewage by converting solar energy,thermal energy（geothermal and industrial heat）and mechanical energy（wind,water flow,vibration and noise）into chemical energy.However,there are few researches on the application of ferroelectric catalysis in environmental pollution treatment,and its reaction mechanism is still unclear.So,the thesis aims at two typical ferroelectric materials,applies them to piezoelectric catalysis and pyroelectric catalysis respectively to degrade phenolic organic wastewater.The details are as follows:（1）Modify the soft bismuth ferrite(Bi₂₅Fe O₄₀)member of traditional ferroelectric material to improve its ferroelectric performance and apply to piezoelectric catalytic degradation of chlorophenol wastewater.Bi₂₅Fe O₄₀ as the precursor irradiated by a high-pressure mercury lamp,a Bi₂O₂CO₃ modified Bi₂₅Fe O₄₀ composite(Bi₂O₂CO₃/Bi₂₅Fe O₄₀)with good piezoelectric catalytic properties was prepared.The photolithography preparation process promotes the oxidation of methanol,which makes part of the Bi on the Bi₂₅Fe O₄₀surface transform to Bi₂O₂CO₃;these in-situ Bi₂O₂CO₃ particles form a heterojunction with the remaining Bi₂₅Fe O₄₀,which can promote the separation of electrons and holes and enhance the efficiency of piezoelectric catalytic degradation.In the experiment of piezoelectric catalytic degradation of 4-chlorophenol by Bi₂O₂CO₃/Bi₂₅Fe O₄₀,the main active species involved in the reaction were superoxide radical（·O₂^-）and hydroxyl radical（·OH）.（2）To further investigate the pyroelectric catalytic degradation of phenolic wastewater by ferroelectric materials for the typical relaxor ferroelectric lead magnesium niobite-lead magnesium titanate（PMN-PT）with stronger ferroelectric properties.The phase of PMN-PT is in the Morphotropic Phase Boundary（MPB）at room temperature.It has excellent ferroelectric properties,and the residual polarization under a voltage of 20 V can reach 22.84μc/cm~2.After 15 hot and cold cycles（ΔT=40℃）,the pyro-catalytic degradation efficiency of phenol,4-chlorophenol,2,4-dichlorophenol,bisphenol A is 100%,100%,87.7%,and 80%respectively.However,H₂O₂ needs to be added into pyroelectric catalysis process to achieve the purpose of activating free radicals.By exploring the pyroelectric catalytic degradation path of 4-chlorophenol,it is found that pyroelectric catalysis degrades 4-chlorophenol into small organic molecules mainly composed of carboxylic acids,and the main active species involved in the reaction is superoxide radicals（·O₂^-）and hydroxyl radical（·OH）.