Abstract: Selective extraction technology is employed to study the separation of manganese oxides and iron oxides in biofilms sampled from natural waters and reviews its applicability. Resulting the extraction technology of artificial culturing biofilms, the hydroxylamine hydrochloride (NH₂OH·HCl) was selected to extract manganese oxides, and sodium dithionite (Na₂S₂O₄) was used to separate manganese oxides and iron oxides. Optimum extraction conditions were determined by changing only one of the experimental conditions such as extraction concentrations, extraction liquid acidity and extraction time and by considering these three factors affecting the extraction effect. Under the selected optimum conditions, the target components in biofilms sampled at different times and sites are extracted with efficiencies between 70.8% and 94.6%, and the affects on nontarget components are negligible(3.3%-11.0%). It satisfies the requirement of the extraction and separation. It shows that selective extraction technology can be applied broadly to the extraction and separation of manganese oxides and iron oxides in biofilms sampled from natural waters.

Key words: natural biofilms, iron oxides, manganese oxides, selective extraction technology