Sphingopyxis sp. YF1吸附镉的特性及其机制

Characteristics and mechanisms of cadmium adsorption by Sphingopyxis sp. YF1

摘要:

【背景】水中的重金属污染是一个严峻的环境问题，严重危害人体健康，利用微生物吸附剂修复重金属污染的水体是一种高效环保的方法。Sphingopyxis能够去除重金属，但是其去除水体中镉的研究很少，且其吸附镉的机理尚不清楚。【目的】以从水体中分离的Sphingopyxis sp. YF1为对象，探究该菌对镉的吸附特性和机制。【方法】分析在不同pH、接触时间及重金属初始浓度条件下YF1活菌和死菌对Cd²⁺的吸附效果，对其进行动力学模型和等温模型拟合，通过扫描电镜和能谱(scanning electron microscopy and energy dispersive X-ray spectroscopy, SEM-EDS)观察镉在活菌和死菌细胞表面的富集，并通过傅里叶变换红外光谱(Fourier transform infrared spectroscopy, FTIR)和X射线光电子能谱(X-ray photoelectron spectroscopy, XPS)分析确定YF1菌中参与吸附Cd²⁺的官能团，阐明YF1对镉的吸附机理。【结果】当pH值为3.0-5.0时，随着pH值的升高，活菌与死菌的镉吸附量都随着增加，pH值为5.0-7.0时，活菌与死菌的镉吸附量均无较大变化，吸附主要发生在前10 min，之后吸附速率逐渐降低，活菌和死菌吸附Cd²⁺的过程更符合准二级动力学模型，表明菌体对镉主要是以化学吸附的方式进行；活菌和死菌等温模型拟合都更符合Langmuir模型，说明YF1对Cd²⁺的吸附为均相吸附；活菌和死菌对Cd²⁺的吸附量分别达到36.20 mg/g和62.98 mg/g；吸附后的活菌和死菌的细胞表面均有Cd(II)沉积在菌体表面，活菌和死菌的-OH、C-(O,N)和-NO₂等基团参与了镉的吸附。【结论】Sphingopyxis sp. YF1菌具有较强的Cd²⁺去除能力，该菌株在去除水体Cd²⁺方面具有良好的应用前景。

Abstract:

[Background] Heavy metal pollution in water is a serious environmental problem posing a severe threat to human health. Using microbial adsorbents to remediate heavy metal-contaminated water is an efficient and eco-friendly method. Sphingopyxis is capable of removing heavy metal pollution, while little is known about the mechanism of the removal of cadmium from water by Sphingopyxis. [Objective] To reveal the cadmiumadsorption efficacy and mechanisms of Sphingopyxis sp. YF1 isolated from water. [Methods] The adsorption of Cd²⁺ by live and dead cells of strain YF1 under different pH, contact time, and initial concentrations of Cd²⁺ were analyzed. Kinetic and isothermal models were fitted to investigate the cadmium adsorption characteristics of this strain. Scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM-EDS) were employed to observe the accumulation of cadmium on the surface of live and dead cells. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) were employed to identify the functional groups involved in the adsorption of Cd²⁺by YF1 cells, so as to elucidate the adsorption mechanism. [Results] With the rise in pH, cadmium adsorption of both live and dead cells increased within the range of pH 3.0–5.0 and did not change greatly within the range of pH 5.0–7.0. The adsorption mainly occurred in the first 10 min, and then the adsorption rate gradually decreased. The process of Cd²⁺ adsorption by live and dead cells was more in line with the pseudo-second-order kinetic model, which suggested YF1 mainly adopted chemisorption. The adsorption of Cd²⁺ by both live and dead cells was better fitted by the Langmuir model, indicating the adsorption of Cd²⁺ by YF1 was homogeneous. The maximal adsorption capacity of Cd²⁺ by live and dead cells reached 36.20 mg/g and 62.98 mg/g, respectively. Cd(II) was deposited on the surface of both live and dead cells after adsorption, and -OH, C-(O,N), and -NO₂ groups were involved in the adsorption. [Conclusion] Sphingopyxis sp. YF1 has high Cd²⁺ removal ability and is promising in the removal of Cd²⁺ from water.