Study On The Technology And Mechanism Of Electrochemical Treatment Of Nickel Wastewater And Dye Antibiotic Wastewater

In recent years,water pollution has shown the characteristics of diversification and persistence,and the emergence of more and more emerging pollutants has made environmental water governance face severe challenges.Heavy metals,printing and dyeing,pharmaceutical and other organic wastewater pose a great threat to the survival of human beings and other organisms in nature.Electrocoagulation is a widely used technology to treat heavy metal wastewater,and the electrochemical oxidation process with boron-doped diamond（BDD）as an electrode has the characteristics of high efficiency and fast removal of organic pollutants.In this paper,sinusoidal alternating current electrocoagulation（SACC）and unidirectional pulsed electrochemical oxidation are used to remove heavy metals,dyes,and antibiotics in wastewater.Through single factor experiments,the optimal operating conditions of the process were determined,and the treatment efficiency and reaction energy consumption were optimized.The distribution of iron ion configuration and the mechanism of removing heavy metals were determined by Ferron analysis.Scanning electron microscope（SEM）,X-ray diffraction（XRD）,Fourier transform infrared spectroscopy（FT-IR）,and other means were used to characterize the topography,structure,and functional changes of flocculation.The degradation pathway and mechanism of organics were studied by ultraviolet and visible spectrum（UV-vis）,gas chromatography-mass spectrometry（GC-MS）,and other techniques.The adsorption of Ni²⁺and the degradation process of dye and antibiotics were analyzed by dynamic theory.The main conclusions are as follows:（1）Under the optimal operating conditions of p H₀=7,j=7 A·m^-2,t=25 min,c₀(Ni²⁺)=100 mg·dm^-3,Ni²⁺removal efficiency reached 99.56%by SACC.The aggregated iron configuration[Fe（b）]and the precipitated iron configuration[Fe（c）]are the keys to the removal of Ni²⁺.SACC can generate more Fe（b）and has higher Ni²⁺removal efficiency than the direct current electrocoagulation（DCC）.The flocs produced by the SACC process were mainly composed of amorphousα-Fe OOH andγ-Fe OOH mixed phases,while the flocs produced by the DCC process were mainly Fe₃O₄.The adsorption experiment of methyl orange shows that the adsorption capacity of Fe（b）is better than that of Fe（c）.（2）Rhodamine B dye wastewater was treated by BDD electrode electrochemical oxidation technology,and SEM showed that the deposition quality of the diamond film on the electrode surface was very high.Complete discoloration of the dye can be realized under the conditions of p H₀=9,j=40 m A·cm^-2,c（Na₂SO₄）=0.035mol·dm^-3,and the initial concentration of Rhodamine B was 75 mg·dm^-3.By using pulsed electrification,the concentration polarization of the dye on the BDD electrode is effectively suppressed,which is beneficial to improving the degradation efficiency.The degradation of Rhodamine B is mainly due to the destruction of the-N=N-conjugate system and N,N-diethyl.（3）The levofloxacin antibiotic wastewater was effectively degraded by pulsed DC electrochemical oxidation technology.Under the optimal conditions of p H=3,j=30 m A·cm^-2,f=100 Hz,c₀=100 mg·dm^-3,c（Na₂SO₄）=0.035 mol·dm^-3,the chemical oxygen demand（COD）removal rate reaches 94.4%.Increasing the frequency of pulsed direct current and the concentration of pollutants can effectively reduce the occurrence of side reactions that generate hydrogen peroxide on the BDD electrode.The degradation pathway of levofloxacin mainly includes hydroxylation,depiperazinylation,demethylation,defluorination,quinolone epoxidation,and decarboxylation caused by·OH attacking the corresponding site.