Transport of copper(II) ions in humic gel—New results from diffusion couple

The diffusion of Cu(II) ions in humic gel was studied for the first time by the diffusion couple method. Three gel types were used. A basic humic gel (gel A) was prepared from sodium humate by precipitation with HCl. Humic gel with incorporated Cu(II) ions was prepared by two different methods: diffusion of Cu(II) ions into the basic gel (gel B) and precipitation of sodium humate with concentrated CuCl2 solution (gel C). The diffusion couple was realized by connecting two silicone tubes, one filled with humic gel containing Cu(II) ions (gel B or C) and the other filled with the gel lacking metal ions (gel A). The effective diffusion coefficient obtained for the gel A/gel B couple corresponds with results from the method of constant source published in our previous work and is higher than the value obtained for the gel A/gel C couple. Measurements of the diffusion of Cu(II) ions from gels B and C into water showed that there was probably some re-arrangement in the structure of these Cu-humic gels, which corresponds with the forementioned results.