Zhang Zhiqiang, Wang Pan, Zhang Jiao, Xia Siqing
Key Laboratory of Yangtze River Water Environment, Ministry of Education, College of Environmental Science and Engineering, Tongji University, Shanghai, 200092, China,
Environ Sci Pollut Res Int. 2014 Sep;21(18):10823-9. doi: 10.1007/s11356-014-3013-6. Epub 2014 Jun 1.
The removal and mechanism of Cu(2+) and Cd(2+) from aqueous single-metal solutions were investigated by using a novel biosorbent from waste-activated sludge. A series of adsorption experiments was designed to disclose the effects of the key factors on the adsorption capacity of the biosorbent for the metal ions. The mass ratio of the biosorbent to metal ion was optimized as 2 to balance the adsorption capacity and the removal efficiency. A right shaking speed (150 r/min) not only ensured enough contact frequency between the sorbent and the adsorbate but also reduced the mass transfer resistance. The natural pH value (about 5.5) of the metal solutions benefited a high adsorption capacity of the biosorbent and avoided the consumption of acid or base for pH adjustment. The adsorption reactions belonged to the endothermic process between 15 and 45 °C. As the scanning electron microscopy (SEM) images showed, the meshy structure with long chains and many branches was ideal for the biosorbent to quickly capture the metal ions. The energy-dispersive X-ray (EDX) spectra confirmed that the adsorbed metal ions lay in the precipitates of the adsorption reactions. According to the FTIR analyses, the functional groups responsible for Cu(2+) adsorption majorly consisted of O-H, N-H, COOH, CONH2, and the groups containing sulfur and phosphorus, while those for Cd(2+) adsorption contained O-H, N-H, COOH, and CONH2. The differences in the responsible functional groups explained the phenomenon that the adsorption capacity of the biosorbent for Cu(2+) was higher than that for Cd(2+).
采用一种新型的废弃活性污泥生物吸附剂，研究了从单一金属水溶液中去除铜离子（Cu(2+)）和镉离子（Cd(2+)）的过程及机理。设计了一系列吸附实验，以揭示关键因素对生物吸附剂对金属离子吸附容量的影响。生物吸附剂与金属离子的质量比优化为2，以平衡吸附容量和去除效率。合适的振荡速度（150转/分钟）不仅确保了吸附剂与吸附质之间有足够的接触频率，还降低了传质阻力。金属溶液的自然pH值（约5.5）有利于生物吸附剂具有较高的吸附容量，且避免了调节pH值时酸或碱的消耗。在15至45℃之间，吸附反应属于吸热过程。扫描电子显微镜（SEM）图像显示，具有长链和许多分支的网状结构有利于生物吸附剂快速捕获金属离子。能量色散X射线（EDX）光谱证实，吸附的金属离子存在于吸附反应的沉淀物中。根据傅里叶变换红外光谱（FTIR）分析，负责吸附Cu(2+)的官能团主要由O-H、N-H、COOH、CONH2以及含硫和磷的基团组成，而负责吸附Cd(2+)的官能团则包含O-H、N-H、COOH和CONH2。这些负责的官能团的差异解释了生物吸附剂对Cu(2+)的吸附容量高于对Cd(2+)的吸附容量这一现象。
