生物炭和乙醇改性生物炭对铜的吸附研究

为研究生物炭和乙醇改性生物炭的特性及其对铜的吸附能力,选取小麦秸秆为原料,在300、450、600℃条件下热解制备生物炭,用于研究乙醇改性生物炭的产油率、生物炭和乙醇改性生物炭的表面官能团变化、亲水性能及其对Cu~(2+)的吸附特性。结果表明:乙醇改性生物炭产油率随热解温度升高而增加。生物炭和乙醇改性生物炭不同温度接触角范围为122.6°~89.3°和96.0°~68.7°,乙醇改性生物炭亲水性明显高于未经改性生物炭。生物炭和改性生物炭对Cu~(2+)的吸附符合二级动力学模型,生物炭吸附速率常数达1.535 g·mg~(-1)·h~(-1),乙醇改性生物炭为1.073 g·mg~(-1)·h~(-1)。二者对Cu~(2+)的等温吸附过程符合Langmuir等温吸附模型,生物炭和乙醇改性生物炭最大吸附量分别为44.3 mg·g-1和41.7 mg·g-1,说明使用乙醇萃取生物炭生物质油后,仍能保持90%左右的Cu~(2+)吸附效率。

Comparison of copper adsorption onto wheat biochar and ethanol-modified biochar

To test the performance of biochar with and without bio-oil for the removal of heavy metals, wheat straw biochars pyrolyzed at three temperatures(300℃, 450℃, and 600℃)were used and then modified by ethanol solution. The ethanol-modified biochars were pre-pared in 75％ ethanol solution for 12 hours to remove bio-oils from the biochars. The characteristics of the raw and ethanol-modified biochars were analyzed, and batch and kinetic adsorption experiments were conducted. The results showed that more bio-oil production rate was obtained using the ethanol-modified biochar pyrolyzed at higher temperature. The contact angle ranges of the raw and ethanol-modified biochars with water were from 122.6° to 89.3° and from 96.0° to 68.7°, respectively, which meant that the ethanol-modified biochars showed less hydrophobicity than the raw biochars did. Ethanol modification had almost no effect on the adsorption rate of the biochar pyrolyzed at 300 ℃, and decreased the adsorption rate of the raw biochar pyrolyzed at 600 ℃ by 30％, from 1.535 g·mg-1·h-1 to 1.073 g·mg-1·h-1. Ethanol modification only slightly decreased the maximum adsorption capacity of the biochars pyrolyzed at all three temperatures, as the biochar modified with ethanol still had around 90％adsorption capacity of the biochars without ethanol modification. The copper adsorption processes onto the raw and ethanol-modified biochars were well fitted by second-order kinetics and Langmuir adsorption models.