| Eutrophication and cyanobacteria bloom pollution as the main environmental problems,affecting the water quality of surface water at home and abroad,because of its difficult treatment,low efficiency,high treatment cost and so on,has been widely concerned by scholars all over the world.In this paper,activated carbon and herbaceous ash were selected as adsorbents to study the adsorption effect and mechanism of nitrate and phosphate,respectively.A new method of removing nitrate and phosphate ions was put forward by combining adsorption with medium electrophoresis.The following two aspects were studied by means of scanning electron microscopy(SEM)and EDS spectroscopy.(1)adsorption properties and adsorption mechanism of activated carbon for nitrate ion in water were studied.Adsorption-dielectric electrophoresis was used to study the removal of nitrate ion and its influencing factors.(2)the adsorption properties and adsorption mechanism of phosphate ion in water were studied.The adsorption-dielectric electrophoresis method was used to study the removal of phosphate ion and its influencing factors.In addition,the feasibility of direct capture of Anabaena Shui Hua by dielectric electrophoresis was also studied,and the effects of different factors on the removal of cyanobacteria bloom were also studied.In the study of the removal of nitrate ion in water,the following conclusions were obtained:In the study of adsorption removal of nitrate,it was found that the dosage of grass and wood ash was positively correlated with the adsorption removal rate of nitrate.The adsorption results of nitrate on straw ash showed that the adsorption kinetics was in accordance with the quasi-second-order kinetic model,and the adsorption thermodynamic behavior was in accordance with Langmuir model,which belonged to monolayer adsorption.The calculation results of thermodynamic parameters show that the reaction is a spontaneous entropy endothermic reaction.In the study of removal of nitrate by adsorption-dielectric electrophoresis,it was found that the dosage of straw ash was positively correlated with the removal efficiency of nitrate by adsorption-dielectric electrophoresis.Compared with adsorption treatment alone,the whole treatment time was reduced from 24 h to 1.5 h,and the removal efficiency was greatly improved after adsorption-dielectric electrophoresis was applied.Using grass ash as absorbent,the optimum capture voltage of nitrate removal by adsorption-dielectric electrophoresis is 13 V.Under the optimum capture voltage,the electric field intensity on the screen electrode is in the optimal range of trapping grass ash particles,and the particles are captured on the wire,and the removal efficiency of nitrate is the highest.The lower the flow rate per unit time is,the higher the nitrate removal rate is by adsorption-dielectric electrophoresis.The optimum flow rate is 0.335 L/h.SEM characterization results show that the morphology of activated carbon particles changes and the particle size decreases after dielectric electrophoresis treatment.With the increase of specific surface area,the active sites of adsorbed nitrate ions on the surface of particles increased.The results of EDS test showed that the content of nitrogen on the surface of the solution did not change obviously after adsorption-dielectric electrophoresis,which may be related to the characteristics of energy dispersive spectrometer.In the study of phosphate removal by adsorption,it was found that the adsorption kinetics of phosphate by straw ash was in accordance with the quasi-second-order kinetic model.Both Freundlich and Langmuir adsorption isotherms can well describe the thermodynamic behavior of phosphate adsorption by straw ash,and monolayer adsorption and multimolecular adsorption exist at the same time.The calculation results of thermodynamic parameters show that the reaction is a spontaneous entropy endothermic reaction.In the study of removal of phosphate by adsorption-dielectric electrophoresis,it was found that the dosage of straw ash was positively correlated with the removal efficiency of phosphate by adsorption-dielectric electrophoresis.After applying adsorption-dielectric electrophoresis,compared with simple adsorption treatment,the overall treatment time was shortened by more than 90%,and the removal efficiency was greatly improved.Using grass ash as absorbent,the optimum capture voltage of phosphate removal by adsorption-dielectric electrophoresis is 13 V.Under the optimum capture voltage,the electric field intensity on the screen electrode is in the optimal range of trapping grass ash particles,and the particles are captured on the wire,and the removal efficiency of phosphate is the highest.The lower the flow rate per unit time is,the higher the phosphate removal rate is by adsorption-dielectric electrophoresis.The optimum flow rate is 0.335 L·h.SEM characterization and EDS test results show that the particle size of grass ash particles decreases after dielectric electrophoresis treatment.With the increase of the specific surface area of the particles,the grass ash particles can be combined with more phosphate ions,accelerate the adsorption process and improve the removal rate of phosphate ions.EDS test results show that after adsorption-dielectric electrophoresis treatment,The content of phosphorus on the surface of the solution increased,which was consistent with the results of UV-vis spectrophotometry.The following conclusions were obtained in the direct capture and removal of Anabaena bloom by dielectric electrophoresis:(1)the microscopic image-shooting proves that the technology of the medium-electrophoresis can effectively capture the stinking algae of the water,the structure of the captured algae cells is complete,and the outflow of the substance in the cell is not found.(2)under certain conditions,the higher the AC voltage,the higher the frequency,the higher the removal rate of the fishy algae in the water and the adjustment of the voltage,frequency and the like,the removal rate of the stinking algae can be increased by 20%.(3)under the condition of the same conditions as voltage,frequency and flow,the dielectrophoresis method has better removal efficiency for the high-concentration algal bloom-eutrophic simulation solution,and the actual removal capacity of the dielectrophoresis method is gradually improved with the increase of the initial concentration.(4)the flow size has a significant effect on the effect.In the same condition as other conditions,the lower the flow rate of the simulated solution pumped into the water,the better the removal effect of the water.And the flow parameters can be adjusted,so that the removal efficiency of the stinking algae of the Anabaena bloom can be improved by more than 40%by a dielectrophoresis method. |
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