一种纳米级不定形碳对水中四环素的吸附研究

Removal of Tetracycline by a Kind of Nano-Sized Amorphous Carbon

研究了一种新型纳米级不定形碳对水中四环素的吸附作用.结果表明,在Li-Na-K碳酸盐的共熔体系中生成的碳粉对四环素表现出了良好的吸附性能.在298K下,碳粉对四环素的吸附行为更符合拟二级动力学模型和Freundlich吸附等温线,最大吸附容量达到127.76 mg·g-1.热力学计算结果表明,吸附过程是吸热的、自发的,以化学吸附为主.吸附行为表现出明显的p H依赖性,当溶液的起始p H在2~11,p H为4时碳粉对四环素的吸附量最大.溶液中的阳离子对吸附有一定的影响,但影响不大,随着阳离子浓度的增加,吸附量在一定程度上逐渐减小.离子交换作用可能是吸附的原理之一,还可能同时存在静电引力、氢键等作用.分别使用0.25 mol·L-1的Ca Cl2和Na Cl溶液进行解吸实验,解吸效率在7.42%~25%,解吸效率较低,说明吸附的化学作用较强.

The experiments were conducted to investigate the adsorption behavior of tetracycline on a kind of nano-sized amorphous carbon,which was synthetized in a molten salt electrochemical system,comprising a eutectic mixture of Li-Na-K carbonates. The results showed that,the carbon powder had a good adsorption performance. At 298 K,the maximum adsorption capacity of tetracycline was 127. 76 mg·g-1. The adsorption data could be well fitted by the pseudo-second-order model and the Freundlich isotherm. Also,the thermodynamic tests for the adsorption were conducted. The adsorption was endothermic and spontaneous reaction with chemical bond as the dominant. The adsorption was p H dependent. The adsorption capacity reached the maximum when solution p H was 4 in the range from 2 to 11. The existence of cations had little effects on the adsorption. The adsorption capacity increased with the concentration of cations to a certain extent. Ion exchange may be one of the adsorption mechanisms,as well as,electric attraction and hydrogen bond. Moreover,desorption experiments were carried out in 0. 25 mol·L-1Ca Cl2 or Na Cl solution respectively. Desorption efficiency ranged from 7. 42% to 25%,which was at a relatively low level. The result indicated that the chemical adsorption process was strong.