Study On Electrosorption Removal Of Heavy Metal Ion From Wastewater

At present, the increase of heavy metal pollution in waters cause the attention by people gradually, this also becomes the difficult problems and focus in study of water environmental pollution at home and abroad. Heavy metal ions in water can be concentrated in aquatic organisms, which may threaten human health through the food chain. The most widely methods adopted to remove heavy metal ions in waste water including chemical precipitation, oxidation, reduction, evaporation, ion exchange, activated carbon adsorption and flotation, etc. However, there are many drawbacks, such as operational difficulties, high cost, easy to cause secondary pollution. To solve these problems, electroadsorption were applied to remove heavy metal ions from wastewater in our study, which is a new water treatment technology developed in nearly 60 years with the advantages of low energy consumption and no secondary pollution. So it is of great potential and broad prospect in the field of water treatment.This experiment used electrosorption by composite electrode to remove Ni2+,Cu2+ ion of aiming at simulating wastewater which contained copper ion and nickel ion. Firstly, the adsorption equilibrium time was fixed, while the influence of different pH, electric potential, initial concentration on the effect of adsorption Ni2+,Cu2+ ion were discussed, respectively. As the results revealed, when pH was among 6 and 7, the effect of Ni2+ on electrosorption is best; but as pH was decreased to between 5 and 6, the effect of Cu2+,s electrosorption is obvious. In the designed voltage range, the higher the voltage enhanced, the more favorable adsorption on Ni2+,Cu2+ showed. However, the occurrence of electrolysis limited the voltage increases. With the initial concentration of Ni2+ and Cu2+ reduced, the adsorption effect became pronounced. Further work was conducted to investigate the effect of voltage on the adsorption of Ni2+,Cu2+ ion by the analyzing adsorption kinetics and adsorption thermodynamics. The results can be summarized as follows:The process of electrosorption by composite electrode for heavy metal ions conformed to Lagergren kinetic equation and second order kinetics equation. The latter showed better fitting results than the former. Because Lagergren kinetic equation can only describe the initial stage of electrosorption by composite electrode for heavy metal ions, but Lagergren second order kinetics equation can be a good description on the whole process of electrosorption for heavy metal ions. Composite electrodes with electrosorption on the Ni2+,Cu2+ ion was consistent with Freundlich equation and Langmuir equation. Indicated electrosorption by composite electrode for these two ions is monolayer adsorption.,and the coefficient K was higher with the increase of voltage in the equation, which meant that voltage was an important factor on the effect of adsorption capacity of composite electrodes.Finally, electric desorption regeneration of Ni2+,Cu2+ ion was studied. The result indicated that by several rounds of electric desorption regeneration, the decrease of adsorption rate and desorption rate was not clear. Therefore, desorption regeneration for heavy metal ions is feasible.