| Leachate from waste incineration plant belongs to fresh leachate and has the characteristics of high concentration of organic pollutants and its water quality changes greatly.In order to meet the discharge requirements of the leachate water quality,a combination of"pretreatment+biological treatment+advanced treatment"is usually used to treat such leachate.The reverse osmosis technology is a commonly used advanced treatment process,but the fouling problem of reverse osmosis membranes has become the main limiting factor for the promotion and application of reverse osmosis technology.Studies had shown that the concentration of fulvic acid in the influent of reverse osmosis membrane treating leachate from waste incineration plant was higher,and the fulvic acid-like substance was one of the main organic component of reverse osmosis membrane fouling.Advanced oxidation technology based on sulfate radical?SO4-·?has great advantages in the treatment of refractory organic pollutants,it is considered that the incineration plants could provide electric energy for the electro-activated persulfate,meanwhile a large number of ions in leachate reverse osmosis influent could provide certain conductivity;on the other hand,the waste heat from incineration plants could provide certain heat source for heat-activated persulfate.In this study,electrochemistry integrated with persulfate system and heat-activated persulfate system were used to remove fulvic acid from the reverse osmosis membrane influent,which was the main substance causing membrane fouling,so as to slow down membrane fouling,prolong the service life of reverse osmosis membranes,and provide a basis for the promotion and application of reverse osmosis technology.In this paper,the self-made fulvic acid wastewater(400mg·L-1)was used as the object.Firstly,the removal effect and mechanism of fulvic acid by electrochemistry integrated with persulfate system?EC+PS?were investigated;on this basis,the influence of the initial pH?pH0?and initial PS?PS0?concentration,current density,plate spacing and electrolyte concentration on the efficiency of fulvic acid were investigated by single factor experiment.Secondly,the effect of the temperature,initial pH?pH0?and initial concentration of PS?PS0?on the removal of fulvic acid by heat-activated persulfate system were studied,and the effect of Cl-on the removal of fulvic acid from the system was aslo investigated.Finally,the infiltration of the leachate reverse osmosis membrane from the actual incineration plant was used to investigate the removal effect of fulvic acid with two kinds of persulfate systems by three-dimensional fluorescence spectroscopy and synchronous fluorescence spectroscopy.The main conclusions are as follows:?1?The EC+PS system had the best effect on the removal of fulvic acid,and oxidative removal was the main removal route of fulvic acid,followed by the EC system;while the PS system had no removal effect on fulvic acid.The mechanism of removing fulvic acid in EC+PS system was probably that HClO,·OH,SO4-·and the transition state non-radical PS*formed on the surface of the anode contributed to the removal of fulvic acid.?2?In the EC+PS system,the removal rate of fulvic acid decreased slightly with the increase of pH0 and plate spacing;with the increase of concentration of PS0,the removal rate of fulvic acid increased first and then decreased;when the current density increased,the removal rate of fulvic acid increased;When the electrolyte concentration increased from 1g·L-11 to 3g·L-1,the total removal rate of fulvic acid remained basically unchanged.Overall,concentration of PS0 and current density were the main factors affecting the removal of fulvic acid in EC+PS system.Under the conditions of pH0=7,PS0=9g·L-1,current density=30mA·cm-2,plate spacing=2cm,and electrolyte concentration=3g·L-1,the total removal rate of fulvic acid is up to 95.30%after 360minutes of reaction.?3?In the heat-activated PS system,the temperature had a great influence on the removal of fulvic acid,and the removal rate of fulvic acid increased with the increase of temperature;pH0 had little effect on the final removal rate of fulvic acid;the concentration of PS0 had a great influence on the removal rate of fulvic acid.Under the conditions of reaction temperature of 70°C,pH0=7,PS0=9g·L-1,the removal rate of fulvic acid reached 99.55%after 360 minutes of reaction.The presence of Cl-had a certain inhibition on the removal of fulvic acid.?4?The two kinds of activated PS systems had a very good removal effect on the fulvic acid in the reverse osmosis membrane influent of the actual leachate from incineration plant.The fluorescence peaks of the fulvic acid in the visible light region and the ultraviolet region of the effluent treated by the EC+PS system and the heat-activated PS system disappeared;the removal rates of the fulvic acid in the visible light region and the ultraviolet region were up to 98.65%and 97.80%treated by the EC+PS system;and the removal rates of fulvic acid in the visible and ultraviolet regions were up to 98.10%and 96.96%respectively treated by heat-activated PS system. |
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