Abstract:

The strain HB-4 was screened from heavy metal contaminated soil, identified as Serratia marcescens via 16S rDNA sequence analysis, and had a strong tolerance for Cd²⁺. This strain can grow well when the concentration of Cd²⁺ was up to 300 mg·L^-1 and in that case the maximum adsorption capacity of Cd²⁺ was (154.7±0.9) mg·g^-1. The effect factors of the adsorption of Cd²⁺ by using HB-4 were investigated, including the initial concentration of Cd²⁺, pH, salt concentration and coexisting ions. The results showed that there was no difference in the adsorption capacity when pH was ranged from 3.0 to 8.0. The same results can also be obtained at 8.0% NaCl solution and the removal efficiency were 98.7%±0.2% (Pb²⁺), 44.6%±0.6% (Zn²⁺), 52.7%±0.1% (Cu²⁺) and 64.2%±0.3% (Cd²⁺), respectively, when Pb²⁺, Zn²⁺, Cu²⁺ and Cd²⁺ coexisted in solution. According to desorption experiment, the desorption rate was less than 2% and it demonstrated that HB-4 performed the best on adsorption of Cd²⁺. The distribution of intra-and extracellular cadmium was studied, as well as the results from SEM, XPS and FTIR. It suggested that the mechanism of adsorption of Cd²⁺ by HB-4 contained extracellular adsorption and intracellular uptake.

Key words: cadmium pollution, adsorbent, Serratia marcescens, adsorption, desorption, extracellular adsorption, intracellular uptake

摘要：

从重金属污染土壤中筛选出1株对Cd²⁺具有高耐受能力和高吸附容量的菌株HB-4，经16S rDNA序列分析鉴定为粘质沙雷氏菌（Serratia marcescens）。该菌株能在Cd²⁺浓度为300 mg·L^-1的条件下正常生长；对Cd²⁺的最大吸附量为（154.7±0.9（ mg·g^-1。考察了Cd²⁺初始浓度、pH、盐浓度以及共存离子对HB-4吸附Cd²⁺的影响，结果表明：pH=3.0~8.0时，对吸附效果无影响；NaCl含量为8.0%时，菌株对Cd²⁺的去除率仍可达到49.9%±0.1%；Pb²⁺、Zn²⁺、Cu²⁺与Cd²⁺共存时，几种重金属离子的去除率分别为98.7%±0.2%（Pb²⁺）、44.6%±0.6%（Zn²⁺）、52.7%±0.1%（Cu²⁺）和64.2%±0.3%（Cd²⁺）。解吸实验证明了HB-4对Cd²⁺极强的吸附能力，洗脱液pH=7.0时，解吸率小于2%。检测了细胞内外镉的分布情况，并利用SEM、XPS和FTIR对吸附机理进行了研究，推断HB-4对Cd²⁺的吸附机理为胞外吸附和胞内摄取。

关键词: 镉污染, 吸附剂, 粘质沙雷氏菌, 吸附作用, 解吸, 胞外吸附, 胞内摄取