| In recent years, the rural domestic waste and landfill leachate has become a serious pollution source that is harm to rural human settlement and life health. It is of great significance to study the leachate treatment technology which is feasible and suitable to rural technology and financial condition. The adsorption technique with the advantages of remarkable effiency, convenient operation and maintenance and low cost is appropriate to be used in the rural area widely. In this study, the environmental mineral materials (clay and zeolite) and industrial waste materials (slag and fly ash) which are abundant, cheap and easily available were used as the adsorbent for rural landfill leachate treatment. The effects of contact time, initial pH, initial concentration and adsorbent dosage on adsorption efficiency were investigated in batch experiments. In addition, the adsorption mechanism of every material was also explored. Moreover, the effective adsorbent materials were combined as the composite adsorbent, and the rural landfill leachate removal efficiency of the constructed wetland with the composite adsorbent as the substrate was also investigated.In consideration of batch adsorption experiment results of four materials, operability and operating costs, the contact time of 120min, adsorbent dosage of 10g/200mL, initial leachate concentration and pH of natural value can be used as practical operation parameters. And under this condition, the removal efficiency of zeolite for normal pollutants (COD, NH3-N,TN, TP) in landfill leachate was better, which the removal rates were 37.54%, 62.91%,34.48% and 27.73%, respectively. The removal efficiency of slag for heavy metals (Cr, As,Cd, Ni and Pb) was preferable, and the removal rates were 81.79%, 35.99%, 97.26%, 74.89%and 91.19%, severally.The isothermal dates of four adsorbents for various pollutants in landfill leachate could be well described by the Freundlich adsorption model, and the experimental adsorption capacity was almost closed to the calculation. The kinetic dates were fitted well with the pseudo-second-order model, the chemisorption was the dominant mechanism.The zeolite and slag with well efficiency were combined as the composite adsorbent, the priority (optimal levels) of influence factors for the composite adsorbent was mass ratio(1:5) >pH (5) > dosage (30g), but there was no significance of pH and adsorbent dosage for the removal efficiency.The constructed wetland used composite adsorbent as the substrate had a good removal efficiency for rural landfill leachate. The removal rate of COD was 50?60%,the effulent concentration of NH3-N and TN reached the requirement of GB16889-2008, and the heavy metal removal rates were up to 85%?90%. But the organic pollutants of 16 kinds of Polycyclic Aromatic Hydrocarbons (PAHs) were not removed from the landfill leachate by the constructed wetland. |
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