Microbial removal of Fe(III) impurities from clay using dissimilatory ironreducers

Fe(III) impurities, which detract refractoriness and whiteness from porcela in and pottery, could be biologically removed from low-quality clay by indi genous dissimilatory Fe(III)-reducing microorganisms. Insoluble Fe(III) in clay particles was leached out as soluble Fe(II), and the Fe(III) reduction reaction was coupled to the oxidation of sugars such as glucose, maltose a nd sucrose. A maximum removal of 44-45% was obtained when the relative amou nt of sugar was 5% (w/w; sugar/clay). By the microbial treatment, the white ness of the clay was increased from 63.20 to 79.64, whereas the redness was clearly decreased from 13.47 to 3.55.