改性污泥基生物炭的制备及其对Cd^2+的吸附特性研究

Preparation of modified sludge-derived biochar and the adsorption characteristics of Cd^2+

为了提高废水中Cd^2+的去除效率并获得高效、低成本吸附剂,以市政污泥为原料,在300℃和500℃条件下限氧热解制备生物炭(BC300和BC500)并用NaOH进行改性(NC300和NC500)。通过元素分析、扫描电镜和傅里叶红外光谱等方法对污泥基生物炭进行表征,运用吸附动力学和吸附等温线系统研究了改性前后污泥基生物炭对Cd^2+的吸附特性。结果表明:与未改性的污泥基生物炭相比,改性污泥基生物炭的极性降低,疏水性增强;碱改性炭表面具有更多的-CH2-,C=O和C-O等官能团,有利于水体中Cd^2+的吸附;4种污泥基生物炭对Cd^2+的吸附过程符合准二级动力学方程和Freundlich等温吸附模型,NC300和NC500对于Cd^2+的最大平衡吸附量较改性前分别提高了2倍和1.1倍。

To improve the removal efficiency of Cd^2+during wastewater treatment and obtain a kind of adsorbent with low cost and high efficiency,biochar( BC300 and BC500) were prepared by oxygen-limited pyrolysis at 300 ℃ and 500 ℃ using municipal sludge as raw material,and modified by NaOH( NC300 and NC500). The sludge-derived biochar was characterized by elemental analysis,scanning electron microscopy( SEM) and fourier transform infrared spectroscopy( FTIR). The adsorption characteristics of Cd^2+on the sludge-derived biochar before and after modification were studied by adsorption kinetics and adsorption isotherm. The results showed that compared with the unmodified sludge-derived biochar,the modified sludge-derived biochar shows lower polarity and higher hydrophobicity. There were more-CH2-,C = O and C-O functional groups on the surface of alkali-modified biochar,which was conducive to the adsorption of Cd^2+in water. The adsorption process of Cd^2+on four kinds of sludge-derived biochar fitted the pseudo-second-order kinetic equation and Freundlich isothermal adsorption model. After modification,the maximum equilibrium adsorption capacity of NC300 and NC500 for Cd^2+increased by 2 times and 1.1 times,respectively.