Modification Of Activated Carbon Intensified By High Gravity And Its Treatment Of Phenol-Cr(Ⅵ) Composite Wastewater

With the rapid development of our industrialization process,the pollution of industrial wastewater has attracted widespread attention.In particular,the treatment of composite wastewater with the coexistence of organic compounds and heavy metals has become a difficult problem to be solved.In industry,it is mainly processed by separate step method,which has many problems such as complicated procedures and long operation time.Therefore,it is critical to develop a new technology that can simultaneously remove organic matter and heavy metals from wastewater.Activated carbon can be widely used as adsorbent,catalyst and catalyst support in the field of water treatment because of its stable properties and low price.Activated carbon catalytic ozonation technology utilizes the catalytic action of activated carbon to catalyze the decomposition of ozone to generate hydroxyl radical（·OH）with stronger oxidation capacity to accelerate the degradation of organic pollutants in water.In addition,heavy metal ions in wastewater can be effectively removed by the adsorption of activated carbon.For the activated carbon catalytic ozone oxidation technology,the conventional gas-liquid contact reactor has the problem of limited ozone mass transfer,which leads to low ozone utilization rate and low organic matter treatment efficiency.How to strengthen the gas-liquid mass transfer and decomposition of ozone become the key,and ozone decomposition is related to the active components on the surface of activated carbon.For the adsorption process of heavy metals,how to improve the liquid-solid mass transfer and adsorption efficiency has become the focus of research.Based on this,the process intensification method and activated carbon modification aim to simultaneously improve the performance of heterogeneous catalytic ozonation and adsorption.Based on the characteristics of enhanced inter-phase mass transfer and reaction by high gravity,the modification of activated carbon intensified by high gravity and its treatment of phenol-Cr（Ⅵ）composite wastewater is proposed.Rotating packed bed（RPB）is used as process intensification equipment,and activated carbon is used as adsorbent,catalyst and carrier filler.The gas-liquid mass transfer process of heterogeneously catalyzed ozone,Liquid-solid mass transfer process in the preparation of supported catalyst and Cr（Ⅵ）adsorbed by activated carbon,And the adsorption catalytic process of simultaneous removal of phenol and Cr（Ⅵ）from composite wastewater was investigated.Improve the ozone utilization rate and liquid-solid adsorption efficiency of the system,and further solve the problem of complex step-by-step processing procedures in the actual industry.Combined with catalyst characterization,adsorption equilibrium and adsorption kinetics,the removal behavior and mechanism of phenol and Cr（Ⅵ）in RPB was revealed.And the synergistic mechanism of simultaneous removal of phenol and Cr（Ⅵ）in RPB was elucidated by DFT calculation.The main research contents and results are as follows:（1）Activated carbon catalyzes ozonation of phenol wastewater and is enhanced by high gravity technology.The TOC removal rate(η_TOC)of RPB/O₃/AC system can reach 91%by adjustingβ、C_O3、Q_L/Q_G and initial p H.Compared with BR/O₃/AC and RPB/O₃ systems,the improvement was 24.78%and 34.77%,respectively.The apparent signal peaks of·OH and O₂·^-were detected by EPR,which revealed the catalytic decomposition of ozone by activated carbon.（2）The adsorption of heavy metal Cr（Ⅵ）ions in water by activated carbon is enhanced by high gravity technology.The removal rate of Cr（Ⅵ）by activated carbon in high gravity field was 89.4%,which was 21.7%higher than that of the traditional adsorption device.The adsorption of Cr（Ⅵ）by activated carbon in RPB conforms to the quasi-second-order kinetic model,and the adsorption equilibrium conforms to the Freundlich isothermal adsorption model,indicating that the rate control step of this process was chemisorption and was a multi-layer adsorption process.Combined with the analysis of intraparticle diffusion model fitting,membrane diffusion and internal diffusion dominated the entire adsorption process.The results of characterization analysis showed that the adsorption mechanism of Cr（Ⅵ）on activated carbon was mainly due to the interaction between the acidic oxygen-containing functional groups on the surface of activated carbon and Cr（Ⅵ）,including hydrogen bonding and coordination complexation.（3）The Fe-Mn Ox/AC was prepared by high gravity method.RPB accelerated the adsorption equilibrium and promoted the uniform dispersion of the active components on the surface of the carrier by enhancing the micro-mixing and liquid-solid mass transfer,which is beneficial to the improvement of catalytic performance.Fe and Mn elements were successfully loaded into the AC carrier in the form of Fe₂O₃、Fe₃O₄ and Mn O₂,respectively.The mineralization rate of phenol in Fe-Mn Ox/AC（RPB）prepared by RPB for 45 min was 7.37%higher than that in traditional stirred reactor for 10 h.XPS analysis showed that there was charge transfer between Mn（IV）/Mn（III）,Mn（III）/Mn（II）and Fe（III）/Fe（II）.Mn（IV）and Fe（III）were active sites that could adsorb and dissociate with O₃ to promote the generation of·OH.（4）The high gravity technology for simultaneous treatment of phenol and Cr（Ⅵ）in wastewater was proposed.With Fe-Mn O_X/AC as RPB filler,the mineralization efficiency of phenol in the composite wastewater can reach 98.54%.the mineralization rate of phenol was98.5%at 60 min,and the removal rate of Cr（Ⅵ）reached 99%at 100 min.Compared with AC/O₃ and Fe-Mn O_X/AC system,the removal rate of Cr（Ⅵ）increased by 5.63%and 34.74%,respectively.Compared with the AC/O₃ and Fe-Mn O_X/AC/O₃（phenol）systems,the phenol mineralization rate increased by 11.37%and 2.41%,respectively.Fe-Mn O_X/AC has a good effect on catalytic ozone oxidation and adsorption of Cr（Ⅵ）in high gravity field.（5）Based on first-principles density functional theory（DFT）,the synergistic mechanism of the composite system was revealed.And the results show that the values ofΔE_ads the Lewis acid and oxygen vacancies decreased to-1.79 e V and-4.26 e V on Fe-Mn O_X/AC after adsorption of chromium,respectively.Charge density difference analysis（CDD）showed that there is electron transfer between Cr and Fe、Mn,the Cr acts as a donor and gives charges to Fe and Mn,which further affects the adsorption and decomposition of ozone,so as to achieve its co-catalytic effect.The synergistic effect in the system was confirmed by NH₃-TPD and EPR.