用紫外分光光度法研究了pH值对壳聚糖螯合Cu(II)的影响。通过显微图像、X衍射图谱及红外光谱对沉淀物进行分析。结果表明，随体系pH值增加，壳聚糖碳链上的活性基团与铜离子的螯合能力增强。溶液体系pH=5~6时，螯合物的稳定常数最大值为1.1×108；当pH接近7时，部分螯合产物析出导致稳定常数降低。酸性条件下pH值的变化对螯合物的配位比(n)无明显影响，壳聚糖–铜螯合物的配位比n=2。通过调节pH值可使溶液中壳聚糖铜螯合物析出，随pH增加，Cu2+浓度降低，当pH约为9时，Cu2+浓度达最小值1.5 mg/L。壳聚糖的主要活性基团–NH2与铜离子发生螯合，反应生成壳聚糖-铜。

Heavy metal ions in water or soil are serious pollution, and human health is seriously endangered by pollution. The removal of heavy metal ions quickly and efficiently has become an important research field. Chitosan is a natural high molecular polymer with excellent flocculation and metal chelation. The effect of pH values on the stability constant and chelation properties of chitosan chelated Cu2+ was studied by ultraviolet spectrophotometry in this work. The chelation performances of chitosan to copper ions were investigated with the pH value increasing from 1 to 9. The experimental results showed that the chelating ability of active groups on chitosan carbon chain with copper ion was enhanced with the increase of the pH value. When the pH values of the solution system ranged from 5 to 6, the stability constant of the chelate was the maximum value of 1.1×108, when the pH was close to 7, some chelate products precipitated and the stability constant decreased. The change of pH value had no obvious effect on the coordination ratio (n) of the chelate under acidic conditions and the ratio (n) was 2. The chitosan-Cu(II) chelate could be separated out by adjusting the pH value of the solution. With the increase of pH value, some floccules precipitated from the solution and the concentration of Cu2+ decreased. When the pH value was about 9, the Cu2+ concentration reached a minimum value of 1.5 mg/L. The precipitate of chitosan reacted with copper ions was analyzed by microscopic image, X-ray diffraction pattern and Fourier transform infrared spectroscopy (FT-IR), the results showed that the main component of the precipitate was chitosan-Cu(II) formed by chelation of –NH2 with Cu2+. This study could provide a theoretical basis for the removal of metal ions by chitosan.