氨氮在膨润土改性黄土衬垫层中的吸附和扩散行为研究

Adsorption and diffusion behavior of ammonium on bentonite modified loess liners

膨润土改性黄土可以用作生活垃圾填埋场底部衬垫层。然而,污染物在膨润土改性黄土衬垫层中的吸附和扩散行为尚不明晰,无法对该类衬垫层的截污性能进行准确评价。研究向黄土中掺入质量占比为15%和30%的膨润土,通过开展批式吸附试验和扩散试验,研究氨氮在改性衬垫层中的吸附和扩散行为。研究结果显示:当膨润土的掺入量为15%时,氨氮在改性衬垫层上的吸附量与纯黄土衬垫层相比没有明显变化,但扩散速率下降了400%;当膨润土的掺入量达到30%时,氨氮在改性衬垫层上的吸附量增加了1.25倍,而扩散速率下降了420%。Pollutev7.0的模拟计算结果表明,在对膨润土改性黄土衬垫层的截污性能进行评价时,如果不考虑污染物的扩散行为,评价结果将产生3.50~4.75倍误差;而不考虑污染物的吸附行为,则将产生334~382倍误差。研究成果可为膨润土改性黄土衬垫层的截污性能评价提供理论依据。

Bentonite-modified loess has been used as bottom liner material for municipal waste landfills.However,because the diffusion and adsorption behavior of pollutants was not determined,the performance of the bentonite-modified losses could not evaluated.Two bentonite-modified loess liners were tested in the present study,containing 15%bentonite and 30%(by weight)bentonite,respectively.A series of batch adsorption and diffusion tests were conducted to examine the adsorption and diffusion behavior of ammonium in bentonite-modified loess liner.The test results show that the addition of 15%bentonite could not increase the adsorption capacity of ammonium on the modified liner,whereas it could decrease the diffusion coefficients of ammonium in the modified loess liner by about 400%.When 30%bentonite was added,the adsorption capacity of ammonium on the modified liner increased by a factor of 1.25,whereas,the diffusion coefficient dropped by about 420%.Pollute v7.0 model results show that it would produce 3.50~4.75 times errors if the diffusion behavior of pollutants were not taken into account when estimating the performance of the bentonite-modified liner.Whereas,there would be 334~382 times errors in the estimating of the modified liner performance if the adsorption behavior of pollutant was not considered.The results of the present study provide parameters for the evaluation of bentonite-modified loess liner performance.