Three-dimensional Electrocatalytic Treatment Of Dyeing Wastewater Based On Active Material/rGO Hydrogel Particle Electrodes

Electrocatalytic treatment technology has been practically applied in the treatment of hard-to-degrade wastewater such as pharmaceutical wastewater,dyeing wastewater and printing wastewater because of its advantages of stable treatment efficiency,long electrode life,simple operation and its economy.Compared with traditional two-dimensional electrochemical reactor(2DER),the three-dimensional electrochemical reactor(3DER)adopts the filling of particles between the cathode and anode as the third electrode,which is equivalent to generating many microelectrodes under the action of the original electric field improving the degradation of organic waste in water.The particle electrode should have good electrical conductivity,catalytic properties and stability,and its performance has a great impact on the treatment efficiency of wastewater,which is also the focus of current research on 3Delectrocatalytic technology.In this Graduation Thesis,the PAC/rGO hydrogel particle electrode with a sparse three-dimensional porous structure was prepared by assembling particle active carbon(PAC)onto a partially reduced graphene oxide(rGO)hydrogel framework using a low-temperature hydrothermal reduction of GO and PAC in a co-blended manner.The factors influencing the electrocatalytic performance,cycling stability and kinetic catalytic mechanism of the PAC/rGO particle electrode on simulated printing and dyeing wastewater were investigated.Results show that the self-assembly of PAC and rGO occurs to generate hydrogel particles,which circumvents the deposition problems of lamellar and powder materials.At the same time,the loaded PAC still maintains its catalytic effect,which makes PAC/rGO in electrocatalytic degradation of rhodamine B(RhB)solution with faster reaction speed than two-dimensional electrochemical reator,and the process does not cause secondary contamination of RhB degradation intermediates and can maintain stable reuse performance.The kinetic tests on RhB degradation showed that the process is a pseudo-primary reaction,i.e.,the oxidation effect is exerted mainly through the production of hydroxyl radicals.However,the electrocatalytic degradation effect of PAC/rGO particle electrode on RhB solution was limited(79.9%),which was analyzed because the PAC component was not ideal as the active component of the particle electrode due to its own conductivity and limited catalytic performance.To address the problems of poor electrical conductivity and catalytic properties of PAC/rGO particle electrode,MXene(Ti3C2Tx),a new material with high electrical conductivity in two-dimensional lamellar form,was introduced to replace PAC,and MXene/rGO hydrogel particle electrode was also prepared by co-blending low-temperature hydrothermal reduction method.Compared with PAC/rGO,the electrocatalytic degradation of RhB by MXene/rGO can reach 94.2%at a lower dosage(96 mg).The electron transfer rate of MXene/rGO in the process of RhB degradation is much higher than that of PAC/rGO,pollutants can be mostly degraded within 40 min at a voltage of 8 V and a dosage of 192 mg at particle electrodes.MXene/rGO can maintain the high efficiency without causing the problem of secondary contamination of intermediates in the process of RhB degradation.The electrocatalytic degradation of RhB is kinetically analyzed as a pseudo primary reaction,which mainly exerts oxidation effect by generating hydroxyl radicals.However,MXene/rGO has the problem of poor recycling stability,and the performance deteriorated significantly after two repeated uses.The reason for this,based on XPS spectroscopy researching,is that the MXene/rGO particle electrodes are randomly filled between the cathode and anode electrode plates in the form of a fluidized bed,and the contact between the particle electrodes and the anode electrode plates caused by random motion of particle electrodes under aeration conditions during operation exacerbates oxidation problem of the MXene material,making its conductivity deteriorate or even lost.In order to solve the problems of MXene/rGO particle electrode cycling stability and soft hydrogel particles prone to breakage in long-term use,the particle electrodes were filled into a 3D printed self-made polylactic acid(PLA)frame for fixation from the perspective of improving the particle electrode filling method.A multi-electrode plate modified advanced three-dimensional electrolytic reactor was designed and fabricated with 2 cathodes(1 Cr 17Mn6Ni5N stainless steel)and 2 anodes(titanium-coated ruthenium-iridium)filled with bed-fixed MXene/rGO particle electrodes.The degradation effect of this multi-electrode plate electrolytic cell on RhB solution was tested.Results showes that the fixed-bed filled MXene/rGO particle electrode,After three cycles,Degradation of RhB could still reach 96.2%,and the retention of the degradation rate K value calculated from the kinetics was 87.05%,which proved that the advanced three-dimensional electrode electrolytic reactor has better cycling stability.