Experiment Study On Treatment Of Chromium(VI)-containing Groundwater By Modified Fly Ash And Zeolite

As an important industrial raw material, Chromium are widely used inindustrial production. However chromium and its compounds especially hexavalentchromium have cytotoxicity, which can accumulate in the body and have long-termtoxicity effects in human. The serious unexpected groundwater pollution which arecaused by the leakage or explosion of filter solution of chromium slag andwastewater containing chromium in industry production have the characteristics ofintensity pollution,rapidly spreading and difficultly repairing. In order to quicklysolve the hazards problem of groundwater pollution, it is necessary to take effectiverehabilitation measures.The modification methods on adsorbents–fly ash and synthetic zeolite werestudied in the experiment. The mechanism on modifying adsorbent was primarilydiscussed. The main technical parameters were determined on adsorption treatmentof groundwater pollution by modified adsorbents. The key factors of affectingefficiency of removing chromium were revealed.The result show that modified fly ash and modified synthetic zeolite have goodadsorption effects on Cr⁶⁺.The groundwater with Cr⁶⁺concentration of5mg/L can betreated to meet the requirements of groundwater standards in3hours by modified flyash which was modified by0.5mol/L sulfate. The synthetic zeolite modified by0.2mol/L ferrous sulfate solution,20%aluminum chloride solution and0.8g/gchitosan are used to treat the groundwater with Cr⁶⁺concentration of5mg/L,whichmeet the requirements of groundwater standards in2hours. SEM photos show thesurface area and porosity of fly ash and synthetic zeolite after modification weregreatly increased. According to energy spectrum analysis, it can be inferred fromtheincrease of Al content in synthetic zeolite that adsorption depends on the electrostaticadsorption and physical adsorption of [AlO₄]^5-tetrahedron element.The Langmuir equation and Freunlich equation were fitted fly ash and syntheticzeolite modified by ferrous sulfate and aluminum chloride adsorption systemprocessing, zeolite modified by chitosan agree with Langmuir isotherm model, which adsorption capacity were22.37mg/g、2.358mg/g、5.624mg/g and19.802mg/g.