Study On Treatment Of Nickel Citrate Complexation Wastewater By Ultrasonic Enhanced Zero-valent Iron Potassium Persulfate System

Heavy metal have been used in all social circles,which caused serious environmental pollution.Nickel is one of the key targets for heavy metal pollution prevention,which is widely sourced,such as mining and electroplating.In this study,we choose the nickel citrate complex wastewater in the electroplating industry as the treatment target,and the effects of ultrasound(US)enhanced zero-valent iron(Fe0)activated potassium persulfate(PS)advanced oxidation technology on the nickel removal rate in nickel citrate wastewater were investigated.In addition,The activation mechanism of potassium persulfate in this system and the degradation mechanism of nickel citrate in wastewater were investigated.In this paper,affecting factors such as initial nickel concentration,initial pH,initial potassium persulfate concentration,mass ratio of zero-valent iron to potassium persulfate(m),ultrasonic power,and zero-valent iron particle size were further studied.It was demonstrated that under the initial nickel concentration of 50 mg·L-1,the initial pH of 3,the initial potassium persulfate concentration of 450 mg·L-1 the mass ratio of zero-valent iron to potassium persulfate of 0.8,and the ultrasonic power of 600 W,and the size of the valence iron of 75 ?m,the nickel removal rate can achieve 100%in one hour reaction.Through the comparative analysis of the nickel removal rate,the variation of potassium persulfate,and the change law of iron ion in the different systems,the results showed that the ultrasonic and zero-valent iron have a synergistic effect.The effects of ultrasonic power,zero-valent iron dosage and initial pH on the activated potassium persulfate were studied.The results showed that the ultrasonic power increase and the zero-valent iron dosage increase can accelerate the activation of potassium persulfate.The acidic pH is beneficial to the activation of potassium persulfate,because the increase of ultrasonic power will strengthen the cleaning of the zero-valent iron surface and release more divalent iron.The acidic condition can assist the corrosion of the zero-valent iron surface.The increased concentration of divalent iron will accelerate the potassium persulfate decomposition.The free radical inhibition experiments demonstrated that the sulfate radical removal was mainly based on sulfate radical oxidation.The analysis of the infrared spectrum shows that the citric acid nickel breakage mainly destroys the carboxylic acid bond between nickel and citric acid.The mechanism of activation of potassium persulfate in the system was inferred by studying the contribution of various factors of the system to activated potassium persulfate.Ultraviolet spectrum analysis of the citric acid concentration in the system and the variation of the TOC concentration in the system revealed that the nickel citrate breaks in the system is a rapid process and the citric acid mineralization is a relatively slow process;Through the analysis of intermediate products in the reaction process,the degradation pathway of nickel citrate was speculated.