Fe, Mn and me

Abstract

In over 60 years of research, my team and I have focused on Fe/Mn removal and the application of KMnO₄ in drinking water purification, and we have made several technological innovations during this period. In response to the basic need to remove Fe and Mn from groundwater sources in the early days of People's Republic of China, I firstly introduced a catalytic technology involving the application of natural manganese sand produced in China as one of the simplest, cost-effective techniques. During experiments, many phenomena that were inconsistent with conventional theories were observed and a new mechanism was proposed, indicating iron/manganese active films as a catalytic agent instead of MnO₂. These films were found to be attached to the surface of natural manganese sand. Fe/Mn-containing compounds with special structures and catalytic features were identified by applying various analytical methods. Drinking water safety was also strengthened by applying KMnO₄ as a new cost-effective chemical for source waters facing environmental pollution in China. Experiments showed that KMnO₄ can effectively remove many pollutants, including trace organic micro-pollutants, by the combined effects of oxidation and adsorption, which were revealed and confirmed for the first time. Through the application of GC/MS analysis of water samples before and after KMnO₄ treatment of samples from various surface water sources, the oxidation by-products from KMnO₄ were found to be nontoxic. Therefore, KMnO₄ is considered to be a safer chemical in comparison with other conventional oxidants (e.g. HOCl). Previous studies also showed several novel features of KMnO₄, such as enhanced coagulation with chlorine, improved algae removal, and increased removal of organically bound manganese. In particular, the combined use of KMnO₄ and chlorine could achieve the same disinfection effect at much lower (50%) chlorine dosages. In addition, there are various chemicals and substances that can be combined with KMnO₄ to improve decontamination performance. Based on extensive experiments, permanganate compounds were found to be highly efficient in removing heavy metals, e.g., thallium. My research also found that both KMnO₄ and powdered activated carbon were highly effective for removing odors and taste. Therefore, we developed a hybrid combination of these two technologies and successfully applied them in many water treatment plants, not only for taste and odor, but also to remove organic micro-pollutants in drinking water. This paper provides a summary of the aforementioned studies that were conducted by me, in collaboration with water treatment industry experts in China, and my graduate students. As a consequence of these studies, several techniques are now widely used in drinking water production in China.

Keywords: Catalytic film; Compounds of KMnO(4) and Chlorine; Iron; KMnO(4); Manganese.