关键词: 羧甲基纤维素钠, 铜离子, 紫外分光光度法, 螯合, 稳定常数

Abstract:

In order to investigate chelating ability of sodium carboxymethyl cellulose (CMC) on copper ions, the absorption spectra of the copper ion complex with CMC were measured via ultraviolet spectrophotometry. The composition of the complex was discussed and its stability constants were calculated. The experimental results show that CMC exhibits adsorption peak at 196 nm. When c(Cu²⁺)/c(—COO^-) is less than 0.6, the absorption peak of the complex appears at 237 nm, —COO^- group of CMC is the main ligand and reacts with Cu²⁺ in a molar ratio of 2:1 to form complex CMC-Cu²⁺, and the complex stability constant is 1.88×10¹⁰. When c(Cu²⁺)/c(—COO^-) is from 0.6 to 1.0, the maximum absorption peak of the complex appears at 214, 237 nm. —COO^- and —OH are involved in the complexation reaction to form a new complex. When c(Cu²⁺)/c(—COO^-) is greater than 1.0, the maximum absorption is in 214 nm and —OH is the primary ligand. The paper also investigates the removal effect of Cu²⁺ by CMC chelating. Experiments show that CMC-Cu directly precipitates to complexes in the solution, with precipitates as floc. c(Cu²⁺)/c(—COO^-) of 0.5 is the optimal usage of CMC in the supernatant, and the removal rate of Cu²⁺ can reach above 96%.

Key words: CMC, copper(Ⅱ), ultraviolet spectrophotometric method, chelation, stability constant