拟柱胞藻对水体重金属的生物富集作用研究

为探讨水华蓝藻拟柱胞藻(Cylindrospermopsis raciborskii)是否具有重金属富集能力,采用拟柱胞藻干藻粉开展了重金属离子的生物吸附实验。将硫酸铜、铬酸钾、乙酸铅、硝酸银、氯化钴、氯化镍,氯化汞7种试剂用双纯水配制成分别含Cu~(2+)、Cr~(6+)、Pb~(2+)、Ag~+、Co~(2+)、Ni~(2+)、Hg~(2+)为50 mg/L的重金属溶液,调pH为5.5,采用原子吸收分光光度仪检测藻粉2 h、4 h、8 h、12 h及24 h吸附重金属的情况,傅立叶变换红外光谱仪比较分析藻粉吸附前与最终吸附24 h后官能团的变化。结果表明,在温度25℃、pH 5.5、重金属离子浓度为50 mg/L的条件下,拟柱胞藻干藻粉对7种重金属离子表现出不同程度的吸附作用,吸附效果最明显的时间为2 h(Cr6+除外),吸附最强的重金属为Pb~(2+),吸附率高达86.30%,吸附量22.23 mg/g(吸附2 h时),7种重金属离子吸附能力(以2 h吸附率衡量)依次为:Pb~(2+)(86.30%)Hg~(2+)(68.23%)Ag~+(67.82%)Cu~(2+)(67.75%)Ni~(2+)(55.18%)Co~(2+)(34.05%)Cr~(6+)(2.22%);红外光谱分析表明,羟基和羧基可能是拟柱胞藻吸附多种重金属离子的活性官能团。研究认为拟柱胞藻能够快速有效地吸附重金属、降低重金属(尤其是Pb~(2+)、Hg~(2+)、Ag~+、Cu~(2+))引起的水环境污染,从而达到改善水质的功效。

Biosorption of Heavy Metals by Cylindrospermopsis raciborskii

Cylindrospermopsis raciborskii is a fresh water cyanobacteria with strong invasiveness and adaptability and has become the primary algal bloom species in eutrophic lakes and reservoirs in China. Research has shown that C. raciborskii grows fast and dominates the phytoplankton community in low salinity, high temperature shrimp culture ponds and supports shrimp growth. We hypothesized that C. raciborskii also removes heavy metals from shrimp ponds and helps maintain a healthy culture water environment. In this study, the biosorption of seven heavy metals (Cu2+, Cr6+, Pb2+, Ag+, Co2+, Ni2+ and Hg2+ ) by C. raciborskii powder was tested under laboratory conditions. The aim of the study is to investigate the ability of C. raciborskii to remove heavy metals, better understand the relationship between C. raciborskii and water quality in shrimp culture ponds and provide a basis for further development and utilization of C. raciborskii. Heavy metal solutions with Cu2+, Cr6+, Pb2+, Ag+, Co2+, Ni2+ and Hg2+ concentrations of 50 mg/L were prepared at pH 5.5 and 100 mL of each solution was placed in a conical flask. Lyophilized C. raciborskii powder (0.2 g) was added to each heavy metal solution and the flasks were placed in an oscillating water bath at 25oC. The heavy metal concentrations in each flask was determined by atomic absorption spectrophotometer (AAS) at 2 h, 4 h, 8 h, 12 h and 24 h. The metal content of C. raciborskii and the adsorption rate for each heavy metal were analyzed and changes in the functional groups of C. raciborskii after the 24 h treatment were detected by infrared spectroscopy. The algae displayed different adsorption capacities for the seven heavy metals (25 °C, pH 5.5) and adsorption was near equilibrium within 2 h, except for Cr6+. Lead was adsorbed most strongly by C. raciborskii, with an adsorption efficiency of 86.3% and an adsorption capacity of 22.23 mg after 2h. The order of adsorption efficiencies of C. raciborskii for the seven heavy metals after 2 h was as follows: Pb2+ (86.3%) > Hg2+ (68.23%) >Ag+ (67.82%) > Cu2+ (67.75%) > Ni2+ (55.18%) >Co2+ (34.05%) >Cr6+ (2.22%). Infrared spectroscopy indicates that hydroxyls and carboxyls of C. raciborskii are the active functional groups adsorbing heavy metal ions. Thus, C. raciborskii can reduce water pollution problems caused by the heavy metals (especially Pb2+, Hg2+, Ag+, Cu2+) quickly and efficiently, consequently improving water quality.