Simultaneous Removal Of Fluorine And Cadmium From Groundwater By Electrocoagulation

At present,the removal of fluoride and heavy metal ions from groundwater is mainly by chemical precipitation,but there are disadvantages such as large amount of sludge after treatment and difficulty in dehydration.The use of improved parallel monopolar iron plate electroflocculation connection removed fluorine and cadmium from groundwater to reduce energy consumption.The specific research contents and conclusions are as follows:In this paper,the effects of operating parameters including initial pH,current density,electrolyte concentration,plate spacing and electrolysis time on the removal of fluorine and cadmium ions were studied.The results showed that when the initial concentrations of fluorine and cadmium were 5 mg/L and 0.5 mg/L,respectively,the optimum conditions were:initial pH of 11,current density of 9.8 mA/cm²,electrolyte concentration of 0.75 g/L,the plate distance is 0.5 cm and the electrolysis time is 55min.At this time,the fluorine removal rate was 89.12%,the cadmium removal rate was99.99%,and the effluent met the GB5749-2006 standard,the processing cost is about5.78⁸.73 yuan/m³.FT-IR and XRD studies have shown that the removal of fluoride ions is mainly through adsorption and precipitation,and the removal of cadmium ions is accompanied by the reduction process of the cathode.By using pseudo-first-order adsorption kinetics equation and pseudo-secondary adsorption kinetics equation to respectively fit the removal curves of different initial fluorine and cadmium concentrations,it is found that the fluorine removal process conforms to the pseudo-first-order adsorption kinetics equation,and the cadmium removal process is pseudo-Secondary adsorption kinetic equation.Based on the complex composition of groundwater,it is often accompanied by a variety of coexisting ions.In this paper,the effects of coexisting anions and cations on the removal of fluorine and cadmium were studied.The effects of Ca²⁺,Mg²⁺,SO₄^2-and NO₃^-from 0⁵0 mg/L were investigated.The study found that the concentration of Ca²⁺and Mg²⁺is positively correlated with the removal rate of fluorine,the presence of Ca²⁺and Mg²⁺has an inhibitory effect on the removal of cadmium ions.At the same time,it was found that the removal efficiency of Ca²⁺and Mg²⁺by the electroflocculation method was higher than 95.54%.SO₄^2-and NO₃^-have competitive inhibition on fluoride ion removal,and promote the removal of cadmium ion,which can accelerate the removal rate of cadmium ion.The removal rate of SO₄^2-by electrocoagulation method is more than 69.46%.The NO₃^-removal rate is greater than95.05%.In addition,to further explore the application research of electroflocculation process,the iron electrode was used to simultaneously remove fluorine and cadmium through a continuous electroflocculation device.The effects of flow rate,current density and initial influent concentration were discussed.The results show that the use of continuous flow electric flocculation to remove fluoride and cadmium ions also has the effect.When the current is greater than 9.8 mA/cm²,the final effluent meets the GB5749-2006 standard at different flow rates.The best dynamic condition flow rate was 24.7 mL/min and the current density was 9.8 mA/cm² using energy analysis.