玉米秸秆生物炭吸附诺氟沙星的影响因素

Influential factors of the norfloxacin adsorbed on the corn stalk biochars

通过在300℃、450℃、600℃下制备玉米秸秆基生物炭(YM300、YM450、YM600),采用孔径与比表面积分析仪、傅里叶红外光谱仪、Boehm滴定对生物炭理化性质进行表征,研究了在不同因素条件下,生物炭对水溶液中诺氟沙星(NOR)的吸附性能及吸附机理。结果表明,随热解温度的升高,生物炭比表面积与孔容积明显增加,孔径变小,酸性官能团减少。生物炭对NOR的吸附容量并不随比表面积的增大而提高,吸附容量大小顺序为q(YM300)>q(YM600)>q(YM450),主要与低热解温度所得生物炭中存在大量非炭化有机质的吸收-分配作用及丰富的表面功能团有关;升高温度有利于吸附的进行,与升高温度促进了NOR与生物炭间的疏水作用结合相关;随pH值的增加生物炭对NOR的吸附容量先增加后减小,在pH=6.04时达到最大,与静电吸引及氢键作用密切相关;阳离子与NOR存在竞争吸附,离子浓度及类型均影响生物炭对NOR的吸附。

The given paper is to devote itself to a study of the adsorptive features and the governing mechanism in addition to the influential factors of the adsorption,such as the NOR initial concentration,temperature,the pH value,and the cation concentration and its type.For the said research purpose,we have carefully investigated and determined the adsorption capability of the antibiotics on the biochars while trying to elucidate their adsorption characteristic features by producing the 3 cornstalk biochars(YM300,YM450 and YM600) via pyrolysis at the temperatures of 300 ℃,450 ℃ and 600 ℃,respectively.The said biochars for our investigation and determination have been chosen as adsorbents,whereas the norfloxacin(NOR) in the aqueous solution has been selected as adsorbate.Hence,in turn,we have also made efforts to characterize the physical and chemical properties of the biochar for their pore size and specific surface area by means of an analyzer,a set of Fourier Transform infrared spectroscopy,as well as an electronic scanning microscope and Boehm titration.The adsorption properties,the governing mechanism as well as the adsorption influential factors have also been examined and registered,such as the NOR initial concentration,the temperature,the pH value,the cation concentration and its type.The results of our investigation and examination prove that the specific surface area and the pore volume of the biochar tend to increase significantly with the elevation of the pyrolysis temperature,though the pore size tends to decrease correspondingly.Besides,the amounts of the acidic functional groups,such as the carboxylic and phenolic hydroxyl groups on the biochars tend to decrease with the increase of the pyrolysis temperature,thus,the alkalinity of the biochar would be increasing accordingly,too.The NOR adsorption capacity for the biochar can be illustrated in the following order,say,YM300 > YM600 > YM450.But the YM300 with the lower surface area of 5.70 m2/g might be able to enjoy the greatest NOR adsorption capacity,that is,that of 32.38 mg/g.This should be ascribed to the plenty of the non-carbonized organic matter and surface functional groups remaining at the low pyrolysis temperature biochar.As to the adsorptive capacity of NOR to the biohars,it has been found that it increases with the rise of the adsorption temperature,which implies that,higher temperature tends to facilitate the adsorption,for it can promote the combination of the hydrophobic interaction between the NOR and the biochar.On the other hand,the desorption capacity of NOR on the biochar tends to increase first and then decrease in case the pH value can increase from 1.5 to 11.0.In that condition,when the pH value goes up to 6.04,that is,to its maximum value,the adsorptive capacity of NOR on the biochars can be found competitive so far as can be found in the given paper.Besides,the effect of the pH value on the adsorption can also be found mainly associated with the electrostatic attraction and hydrogen-bonding interaction.And,since the cationic tends to be in a competitive adsorptive status in-situ on the biochar,the adsorption capacity of NOR on biochar tends to be affected by the cationic type and its concentration.