Experimental Study On Remediation Of 2,4-dichlorophenol Contaminated Groundwater With Activation Of Persulfate Based On Nanoscaled Magnetic Materials

2,4-dichlorophenol（2,4-DCP）, a kind of typical chlorophenol compounds, has high toxicity. 2,4-dichlorophenol in the environment was mainly come from the preparation of dyes, pesticides, insecticides and pesticides. In situ chemical oxidation technology based on the generation of sulfate radicals have been gradually developed, this paper mainly studies using heterogeneous catalyst to activate persulfate for the degradation of 2,4-dichlorophenol pollutants.Nanoscaled Fe₃O₄, with their large specific surface area, rich surface functional groups, easy solid-liquid separation, could reduce environmental risks and cut the emissions of nanoparticles. These advantages are the reason of using nanoscaled Fe₃O₄ as activator in the field of activation persulfate. But due to the weak activation performance of nano Fe₃O₄, so this paper prepared three activators such as CuO@Fe₃O₄, H2A/Fe₃O₄ and Saponin- Fe₃O₄（S- Fe₃O₄） based on nano Fe₃O₄ for addressing this weakness.The experiment that CuO@Fe₃O₄ activated persulfate to degrade 2,4-dichlorophenol degradation found that when 0.624 g/L CuO@Fe₃O₄（0.002 mM Fe（II） + 0.002 mM Cu（II）） added to activate persulfate, the removal efficiency can reach 96.9% within 180 min. Comparatively, 0.928 g/L Fe₃O₄（0.004 mM Fe（II）） equal to 0.624 g/L CuO@Fe₃O₄ removed 8.1% 2,4-DCP The above experimental results showed that the activation performance could be obviously improved after CuO coated at Fe₃O₄. At the same time, the degradation process followed the pseudo-first order reaction kinetics.The removal efficiency of 100 mg/L 2,4-DCP was 98.5 % when the concentration of H2A/Fe₃O₄ was 2g/L in the existence of 30 mmol/L persulfate. However, when 2g/L Fe₃O₄ was activator, the removal efficiency could only reach 35.1 %. It indicated using H2 A to improve the activation performance of Fe₃O₄ is a practical way.However, the nano Fe₃O₄ as the magnetic activator was easily aggregation, and the two kinds of activators above have not improved the nano Fe₃O₄ dispersion, which would make difficulty in transportation in porous media. So in this paper, a kind of plant-based surfactants called Saponin was used to improve the dispersion. The results of TEM showed that S-Fe₃O₄ has good dispersibility satisfying the desired results. And S-Fe₃O₄ could improve the activation performance of Fe₃O₄. The effects of common ions such as Mg2+、Ca2+、Cl-、HCO3-、NO3- and SO42- in groundwater were studied. In these ions, Cl- and HCO3- have big influence because of the quenching of sulfate radicals. And CaSO4 is slightly soluble solid deposited on the surface of activator to cover the part of active site in water derived from the reaction of Ca2+ and SO42-.For the three kinds of activator above, S-Fe₃O₄ was chosen as an activator through comprehensive analysis, which has the most outstanding dispersion performance to study its transfer performance in the aquifer. The results showed that Fe₃O₄ before modification blockaded on the injection port immediately, and didn’t migrate any more although after the undergroudwater at the rate of 1 m/d flushed. But, S- Fe₃O₄ could instantly migrate at the start of the injection. And it could migrate as the flush of underground water until it flowed out from the outlet at the top.