Study On The Performance Of The Integrated Transfer-capture-release Method In The Treatment Of Pb Polluted Municipal Sludge

After treated by the sewage treatment plant,the sewage turns into lightness.But the pollutants in it are enriched and precipitated in the remaining sludge rather than disappear.The increasing sludge production year by year is bound to become a time bomb igniting the environmental crisis.When enacting the sludge treattment and disposal technology,local governments should give priority to the ones related sludge resource utilization to extend the service life of primary energy.As the main body of"urban mines",the development potential of heavy metal resources shouldn't be ignored.Under the increasingly pressure of strict environmental regulations,investment ofenvironment protection definentely is going to rise.The effective recovery of heavy metals in residual sludeg will provide potential compensate for high sludge disposal costs.Therefore,it is of great practical significance to study the reasonable disposal and utilization technology of sludge.Considering the above problems,a new type of electric sludge removal and recovery device was designed.Instead of DC,we use a square wave power supply with adjustable frequency and amplitude as power supply method.A special self-doped polyaniline/carbon powder/Nafion hybrid modified carbon felt electrode was assembleded and used as cathode,which exhibite excellent Pb²⁺selective adsorption performance.During the electrokinetic process,using the double layer structure on the cathode surface induce the capture of target Pb²⁺inos it.In this experiment,we use lead pollution as an example to verify the effectiveness of the experimental device,the feasibility of the experimental principle.The specific research contents and conclusions are as follows:?1?Based on the traditional fourth-type device,in this experiment,we designed a new type of sludge electrickinetic device composed of a power supply system,a reaction device system and a pH control system.We replace the internal cylindrical electrode with a cylindrical anode of the outer wall,which can significantly increase the effective contact area between sludge and anode plate and improve the overall removal efficiency.More importantly,after reversing the position of the anode and cathode,the direction of the internal electric field changes from the divergence to the centering.It is benefical to the capture of target metals.?2?Preparation and electrochemical performance of self-assembled replaceable self-doped polyaniline/carbon powder/Nafion modified carbon felt electrodes.A self-doped polyaniline nanomaterial with high Pb²⁺selective property was synthesized using chemical oxidation copolymerization method.The morphological characterization shows that the polymer appears as an aggregation of micro-nano-sized non-porous hollow spheres and particles.Due to the existence of-NH₂,-N=,-N-H,-SO₃H fuction groups,the material wons a stronger complexation with Pb²⁺,showing superior adsorption performance compared to other heavy metal ions.The self-doped polyaniline/carbon powder/Nafion modified carbon felt electrode was prepared by the drop coating method.The morphological characterization shows that the mixed material is successfully and uniformly coated on the surface of the electrode.The three-dimensional porous structure of the carbon felt and the rough porous structue of coated layer exposed more electrochemically active sites when reaction.Electrochemical analysis confirmed the existnce of electrochemical activity between modified carbon felt electrode and target Pb²⁺.When using 0.5%mass concentration Nafion solution,the modifeid electrode showed the strongest peak current signal.?3?Determination of the optimal operating parameters of the device.In the frequency range of 100-600 Hz,set EF1-6 according to a gradient of 100 Hz,6 sets of electric repair experiments,the results show that when the power output square wave frequency is 600 Hz,the cathode HER is the weakest,the electric double layer is the strongest,and the trapping Pb2+has the best effect.The square wave frequency of the control power output is unchanged at 600 Hz,and the amplitude of the square wave of the power output is changed according to the voltage gradient of 1 V/cm,1.5 V/cm,2 V/cm,and the corresponding setting of EK1-3 is 4.5 V-0,6.75 V-0V,9V-0 V 3 sets of electric repair experiments?three sets of parallel real average?,the results show that when the voltage gradient is set to 2 V/cm,that is,the output power square wave amplitude is 9 V-0 V,The removal rate of Pb was the highest,64.78%,and the recovery was the largest,63.89%.The characterization of the cathode carbon felt after electrolysis shows that the fiber surface at this time is composed of many three-dimensional layered flower-like nano-cluster structures closely packed,and the formation of this structure should be attributed to the directional production effect of the applied electric field.Corresponding to the Mapping diagram,in addition to the Pb deposition on the surface of the carbon felt,there are still Zn,Cu and other deposition,which is consistent with the adsorption performance verification experiment of the self-doped polyaniline material.XRD results show that the Pb deposited in the cathode is amorphous.XPS comparative characterization results show that the Pb deposited on the carbon felt electrode is a mixture of various Pb3+and Pb2+lead oxides,which may be related to the ORR of the electrode surface,which is consistent with the results of the cyclic voltammetry analysis of the carbon felt electrode.