苯胺黑药高效降解菌(Bacillus vallismortis)胞外聚合物去除重金属的研究

微生物胞外聚合物(Extracellular Polymeric Substances,EPS)在废水中重金属的吸附去除过程中起着非常重要的作用.苯胺黑药高效降解菌(Bacillus vallismortis)对苯胺黑药有良好的降解能力,但对其吸附重金属的性能研究还不充分.因此,本文采用3种方法提取苯胺黑药高效降解菌的EPS,主要考察了p H、温度、底物浓度和时间对重金属去除效果的影响.结果表明,热提法提取的效率较高;p H对金属离子吸附影响很大,当p H7时,随着p H变大吸附量逐渐升高,而温度对吸附量影响不大.EPS对Cu~(2+)、Zn~(2+)的去除为快速表面吸附过程,在第8 min时对Cu~(2+)、Zn~(2+)的去除率分别达到了90.7%、52.3%,EPS对Cu~(2+)、Zn~(2+)的吸附表观上符合拟二级动力学规律.在单一体系中,根据Langmuir方程计算出EPS对Cu~(2+)的最大吸附量为2.155 mg·mg-1,对Zn~(2+)的最大吸附量为0.508 mg·mg-1;Cu~(2+)吸附过程与Freundlich方程拟合效果较好,Zn~(2+)吸附过程与Langmuir方程拟合效果较好.红外光谱分析结果表明,EPS表面的羟基、氨基、酰胺基团、羧基和C—O—C基团都参与了吸附,且Cu~(2+)和Zn~(2+)的吸附位点基本一致,本文的研究结果对工程实践具有一定的理论指导意义.

Study on heavy metals removal by extracellular polymeric substances extracted from aniline aerofloat-degradating bacterium (Bacillus vallismortis)

Extracellular polymeric substances (EPS) play a very important role in heavy metals removal from wastewater through adsorption. Bacillus vallismortis has been found to be efficient in degradation of aniline aerofloat, however, its potential for heavy metal removal is still unexplored. In this study, three methods were employed to extract EPS, and effects of pH, temperature, substrate concentration and time on removal efficiency of heavy metals were investigated. The results show the highest extraction efficiency of EPS was achieved by using heat extraction method and pH played a greater influence than other factors on heavy metals removal. The adsorption capacity of the EPS to heavy metals increased with pH under pH below 7, but the effect of temperature was negligible. Cu²⁺/Zn²⁺ removal by the EPS was found to be a rapid surface adsorption process. Cu²⁺ and Zn²⁺ were removed up to 90.7% and 52.3% within eight minutes respectively. The adsorption process of heavy metals onto EPS followed pseudo second order model. The maximum adsorption capacity of Cu²⁺ and Zn²⁺ calculated from Langmuir isotherm model were 2.155 mg·mg^-1 and 0.508 mg·mg^-1 respectively, under single metal system. The adsorption process of Cu²⁺ was well fitted with Langmuir isotherm model, while the adsorption process of Zn²⁺ was better fitted with Freundlich isotherm model. Infrared spectrum analysis results demonstrate the presence of hydroxyl, amino, amide groups, carboxyl and C-O-C group on the surface of EPS which could be involved in the adsorption of heavy metals, and the Cu²⁺ and Zn²⁺ adsorption siteson the EPS were almost the same. These results will provide a theoretical guidance for practical application of using EPS to remove heavy metals from aqueous solution.