羊栖菜干藻作为生物吸附剂用于去除电镀废水中的重金属

Removal of heavy metals from electroplating wastewater by Sargassum fusiforme biomass

藻类作为一种生物吸附剂用于去除水溶液中单种重金属离子,具有较好的效果,但对共存的多种金属离子去除则相对复杂。本实验利用碱预处理后的羊栖菜藻粉作为海藻吸附剂,研究了不同环境条件对其去除电镀废水中重金属离子[Zn(Ⅱ)、Cu(Ⅱ)、Cr(Ⅵ)和Ni(Ⅱ)]的影响,并通过电镜观察和红外光谱分析其对重金属离子的吸附机理。结果发现,pH 2时Cr(Ⅵ)去除率最高,在pH 6~9时,Cu(Ⅱ)、Zn(Ⅱ)和Ni(Ⅱ)的去除率较高。海藻吸附剂在低剂量(2~4 g/L)投加时,4种重金属的去除率均有不同程度的增加,大于4 g/L时,去除率不再增加。Zn(Ⅱ)和Ni(Ⅱ)的吸附在25 min左右达到平衡,Cr(Ⅵ)和Cu(Ⅱ)稍慢;温度对海藻吸附剂去除Cu(Ⅱ)、Zn(Ⅱ)、Cr(Ⅵ)和Ni(Ⅱ)的影响并不明显。Langmuir模型能更好地描述海藻吸附剂对4种重金属离子的吸附行为,表明它们属于单分子层吸附,海藻吸附剂对Cr(Ⅵ)和Ni(Ⅱ)的最大吸附容量明显高于Cu(Ⅱ)和Zn(Ⅱ)。准二级吸附动力学方程能更好地描述吸附过程,说明吸附方式以化学吸附为主。吸附前后海藻吸附剂的红外光谱分析表明,对重金属的生物吸附主要与羧基有关。研究表明,海藻吸附剂对电镀废水中Cu(Ⅱ)、Zn(Ⅱ)、Cr(Ⅵ)和Ni(Ⅱ)都具有一定的去除效果。

Algal bioadsorbents can effectively remove the single heavy metal ion in aqueous solution, but the removal mechanism of coexisting multiple metal ions was relatively complicated. In this paper, Sargassum fusiforme biomass, pretreated by NaOH, was used to remove heavy metal ions [Cu(Ⅱ), Zn(Ⅱ), Cr(Ⅵ) and Ni(Ⅱ)] in the electroplating wastewater, and the effects of pH, temperature, contact time and biomass doses on the removal efficiency and its adsorption mechanism were investigated. The results showed that the optimum pH in the removal efficiency of Cu(Ⅱ), Zn(Ⅱ) and Ni(Ⅱ) was among 6–9, while for Cr(Ⅵ), it was 2. The removal efficiency increased when biomass doses were elevated from 2 to 4 g/L, but it maintained constant when the biomass doses were higher than 4 g/L. The adsorption equilibrium of Zn(Ⅱ) and Ni(Ⅱ) was reached at about 25 min while for Cr(Ⅵ) and Cu(Ⅱ), it was slightly slow. The influence of temperature on adsorption of heavy metal ions was not obvious. Langmuir model can closely describe the adsorption of heavy metal ions, which indicated the absorption was the monolayer adsorption. The maximum adsorption capacity for Cr(Ⅵ) and Ni(Ⅱ) was significantly higher than that for Cu(Ⅱ) and Zn(Ⅱ). The adsorption kinetic can be described by the pseudo-second order kinetic model,indicating that the adsorption process was mainly chemical adsorption. Fourier transform infrared spectroscopy analysis of the adsorbent before and after adsorption showed that the bioabsorption of heavy metals was mainly related to carboxyl group. The results suggested that the algal adsorbent could effectively remove the heavy metal ions in electroplating wastewater and exhibit a good application prospect.