Simple diffusion method applied in evaluation of metal transport in model humic matrices

Humic acids play an important role in soil and natural water chemistry. Many works dealing with sorption of different toxic chemicals on both solid humic acids and humic sols have been published. This paper focuses on the transport and immobilization of Cu2+ in a humic gel. Use of humic acids in a gel form brings several advantages: it enables preparation of samples with defined size and shape and gives a true picture of natural form of humic acids in soils and sediments. Due to its high affinity for humic acids and a good stability of formed complexes copper was used as a model metal. The two following concepts of nonstationary diffusion were adopted: diffusion from constant source and diffusion from time-variable source of a diffusing matter. In the latter case, effects of time and of the initial concentration of Cu2+ ions source were determined. Usability of an applied experimental arrangement and mathematical description of metal ions transport and immobilization are discussed.