Preparation Of Modified Steel Slag Particle Electrode And Its Performance Of Algae Removal And Inhibition In Three-dimensional Electrocatalytic Oxidation System

With the development of industry and urbanization,the phenomenon of algae outbreak caused by water eutrophication has become one of the important ecological and environmental problems in China.Due to the limitations of mainstream algal control technologies,it is urgent to find new methods for controlling algae.Three-dimensional electrocatalytic oxidation technology overcomes the defects of small specific surface area and low current efficiency of two-dimensional electrode,and it has significant advantages in water treatment.In this technology,the particle electrode is the key factor affecting the electrocatalytic effect.Steel slag is a kind of industrial solid waste,which contains many metals and their oxides,has rich pore structure and large specific surface area.In this paper,a new type of particle electrode was developed with steel slag as raw material to realize the waste utilization of steel slag.At the same time,a three-dimensional electrocatalytic oxidation system was established to study the algae removal performance and mechanism of the system.In this study,steel slag particle electrode was prepared using steel slag as the main raw material.The apparent states and the electrocatalytic algae removal performance of the particle electrode were used as measurement indexes to optimize its preparation conditions.The steel slag particle electrode was modified by ultrasonic impregnation-roasting method to determine the preparation conditions of the modified steel slag particle electrode.The morphological characteristics,chemical composition,magnetic properties and electrochemical properties of particle electrodes were characterized.A static three-dimensional electrocatalytic oxidation system was established by using modified steel slag particles as particle electrode and the effects of electrolyte concentration,particle dosage,tank voltage,initial algae density and algae cell growth period on electrocatalytic algae removal were studied to optimize its operating conditions.And dynamic experiments and repeated tests of particle electrodes were carried out to verify the algal removal performance of the system.Finally,the mechanism of three-dimensional electrocatalytic oxidation for algae removal was explored by studying the adsorption of particle electrodes on algal cells,the generation and change of hydroxyl radicals and mechanism of enhanced algae removal in the electrocatalytic system,the instant algae removal effect of electrocatalytic oxidation and the long-term algal suppression effect of electrocatalytic oxidation.The steel slag,montmorillonite and sawdust were mixed and granulated according to the mass ratio of 60%∶28%∶12%,and then the steel slag particle electrode was prepared by calcining at 800°C for 60 min.The modified steel slag particle electrode was prepared by ultrasonic impregnating the steel slag particle electrode with 30%zinc nitrate solution for 1 hour,drying at 110°C for 3 h,and roasting at 400°C for 2 hours.The steel slag particle electrode and the modified steel slag particle electrode contained O,Mg,Al,Si,Ca,Fe and other elements,and the specific surface areas of them were（2.7256±0.0110）m²/g and（1.2922±0.0049）m²/g,respectively,which was reduced after modification.Magnetic attraction of the two particle electrodes could overcome the effect of gravity since they contained Fe₃O_4.The modified steel slag particle electrode was loaded with 10.75%of Zn O on the surface,which made its electrochemical impedance enhanced by 2.05 times compared with that before modification,and it had stronger electrochemical performance than the steel slag particle electrode.When the electrolyte concentration was 1 g/L,the dosage of modified steel slag particles was 6 g,the tank voltage was 8 V,the initial algae density was 10⁸～10⁹cells/L and algae were in the logarithmic growth period,the three-dimensional electrocatalytic oxidation system reached the best running state with algae removal rate of 58.49%in 10minutes.When the system dynamically circulated 450 m L of algae fluid,the algae removal rate was up to 56.83%in 60 minutes,and the modified steel slag particle electrode still had higher catalytic activity after repeated use.The three-dimensional electrocatalytic oxidation system removed algae through the combined action of electrocatalytic oxidation and adsorption,and electrocatalytic oxidation was dominant in the process of electrocatalytic oxidation.In the electrocatalytic process,the rate constant of·OH produced by the modified steel slag particle electrode electrocatalytic system was 9.29 mol/（L·min）,higher than the 3.20 and 5.08 mol/（L·min）of the two-dimensional electrode and the steel slag particle electrode system,and the modified steel slag particle electrode electrocatalytic system had better alage removal performance.The structure,enzyme and photosynthesis system of algae cell could be damaged by electrocatalytic oxidation,and the algae cells could be instantly removed and the cell growth could be inhibited.The stronger the electrocatalytic oxidation capacity of the system was,the more obvious the effect of removing and inhibiting algal cells were.