The Application Of Zeolite–Nanoscale Zero-Valent Iron Composite In The Removal/Stabilization Of Cu(?) From Aqueous Solution And Contaminated Soils

With the increasing use and release of heavy metals,the heavy metal pollution in environment is more and more serious.In this study,we select the copper?Cu?as research object.On one hand the effects of pH,the initial Cu²⁺concentration,dosage of adsorbent,and temperature on the elimination of Cu²⁺from aqueous solutions were investigated.On the other hand,the zeolite-nanoscale zero valent iron composite were applied to artificial Cu contaminated soils and the efforts were made to demonstrate the performance of the composites in the in situ stabilization of Cu ions.The main contents are as follows:1.The preparation and characterization of zeolite-nanoscale zero valent ironIn this study,the composite of zeolite-nanoscale zero valent iron?Z-nZVI?was synthesized by liquid reduction and characterized by transmission electron microscopy?TEM?and X-ray diffraction?XRD?.The specific surface area was determined using Brunauer-Emmett-Teller?BET?measurement.The XRD patterns of synthesized materials indicated that the heulandite was the mian component of the studied zeolite.The presence of zeolite in the composite resulted in decreased aggregation of iron nanoparticles and improved the surface area.2.The comparison of Cu²⁺removal efficiency between composites with different ratio of Fe and zeolite.The composites with different Fe/zeolite ratio were acquired by changing the dosage of zeolite during synthesis process.The adsorption efficiency of Cu²⁺by Z-nZVI with different ratio of Fe and Zeolite was investigated.The results showed that Z-nZVI with 1:6 ratio of Fe to Zeolite performed best.3.The removal of Cu²⁺from aqueous solution by zeolie-nanoscale zero valent ironFirst of all,the adsorption kinetics of Cu²⁺by zeolite,nZVI and Z-nZVI were compared,from which we know that the Z-nZVI performed best.The adsorption kinetics of Cu²⁺fitted better with pseudo-second order kinetics than with pseudo-first order kinetics.When it comes to the effect imposed by dosage,increasing removal efficiency can be observed with the increased addition of Z-nZVI.The equilibrium data were analyzed against the Langmuir and Freundlich isotherm models,which revealed that the Langmuir isotherm was the most suitable model for describing Cu²⁺adsorption with the relative coefficient of Langmuir was greater than Freundlich's.In addition to that the maxum adsorption capacity obtained from the simulation is 793.651mg·g^-1Fe⁰ and 909.091mg·g^-1Fe⁰ respectively at 25?and 45?.It can be inferred that with the elevation of reaction temperature,the removal process of Cu²⁺can get promoted.The desorption rate of Cu²⁺from Z-nZVI is between 0.2-1.5%which is negligible,and this means that it is difficult for the adsorbed Cu²⁺on the surface of this material to be desorbed to aqueous solution again.So Z-nZVI is one of the excellent adsorbent which possesses high adsorption capacity and meanwhile with low desorption amount.And the results of the three level orthogonal experiment showed that the optimal condition for Cu²⁺adsorption by Z-nZVI was achieved through adding 5.25g·L^-1 Z-nZVI to the solution with a pH of 3 and at a temperature of 45?.Results support the potential use of the Z-nZVI composite for the removal of Cu²⁺from aqueous solution.4.The in situ stabilization of copper ion by zeolie-nanoscale zero valent iron?1?The performance of zeolite,nZVI,Z-nZVI in the stabilization of Cu²⁺in soils were investigated,which revealed that the materials added into the artificial polluted soils all played a role in the reduction of DTPA-Cu concentration.Of the three kinds of materials,nZVI and Z-nZVI performed better than zeolite and the dosage-effect can be observed in the stabilization of Cu²⁺by nZVI.?2?The concentration of DTPA-Cu leached from the polluted soils increased with the elevation of Cu²⁺concentration in soils.And the amount of Cu leached from the soils is related to the total content of Cu in soil,in which the relative coefficient were all above 0.98 which means a great relevance.?3?The temperature also made a difference in the stabilization of Cu in soil.Comparing the results obtained under the condition of room temperature and 40?,we can get the conclusion that raising the temperature can help stabilize the Cu ions in soil.What's more,the performance of Z-nZVI was significantly better at higher temperature.?4?It can be inferred from the results of the correlation analysis that the relation between different Copper fractions was different under different treatment,which proved that the transformation between different fractions can be significantly influenced by various surrounding environment.Besides,the content of residual Copper in soils treated with different materials increased with time,which proved the stabilization of Copper ion.Among the three different materials including zeolite,nZVI and Z-nZVI,the last one namely Z-nZVI performed best in the stabilization of Copper ion.