High-Quality Inorganic Red Pigment Prepared by Aluminum Deposition on Biogenous Iron Oxide Sheaths

Abstract

Naturally occurring tubular iron oxides produced by aquatic bacteria in Leptothrix spp. are promising raw materials for hematite-based red pigments because of the higher heat resistance as compared with chemically synthesized hematite compounds. Here, we report iron oxide red pigments prepared through an additive deposition of aluminum on culture-based biogenous iron oxide (cBIOX) sheaths using an artificial culture system of L. cholodnii strain OUMS1. The heat-treated Al-containing cBIOXs exhibited elevated chroma and lightness along with increasing Al contents and enhanced thermal stability of color tones to repetitive heat treatments. XRD analysis showed a monophasic pattern of hematite in the Al-rich cBIOX after heating at a wide range of high temperatures. Micromorphology analyses revealed that putative Al oxide regions present among hematite particles plausibly prevented the grain growth of hematite during heat treatments. The results therefore demonstrate that the bioderived Al-rich iron oxide sheaths can serve as innovative inorganic red pigments feasible for industrial applications.

Eco-Benign Orange-Hued Pigment Derived from Aluminum-Enriched Biogenous Iron Oxide Sheaths

“…Previous studies have shown that the inclusion of Al in the chemically synthesized hematite-based pigments produced yellowish-red hues 22 − 24 and that the additive deposition of Al in BIOX-derived pigments resulted in an increased yellowish intensity. 21 Using a two-step method, 19 we have prepared highly enriched Al-containing cBIOX sheaths by the addition of 10 mM AlCl 3 solution over various concentrations of ZnSO 4 . Tube-shaped sheaths of cBIOX were successfully obtained at low concentrations of ZnSO 4 (≤10 mM), while an excess of sulfate ions might hinder the formation of cBIOX.…”

“…Color tone values (CIE L * a * b *) of heat-treated samples were measured by spectrophotometry (CM- 2600d, Konica–Minolta Inc., Tokyo, Japan) using a CIE standard illuminant D65 and SCI mode as previously described. 21 Powder samples were loaded into cylindrical pits (φ 8 mm, 0.5 mm in depth) on glass holders using a plastic film to flatten the compacted powders’ surface for accurate measurements. A commercially available iron oxide pigment MC-55 (Morishita Bengara Kogyo Co., Ltd., Mie, Japan) was used as the color reference.…”

“… 19 , 20 Moreover, the additive elements deposited on the BIOX sheaths could readily improve the color tones in heated products, indicating that the BIOXs are easily tunable materials. 21 Herein, we describe new orange-hued iron oxide pigments with readily modifiable hues by changing the elemental composition in the BIOXs.…”

“…In ancient times, hematite pigments have been used for coloring murals and ornaments; nowadays, owing to their extremely low toxicity, wide availability, and high hiding power, these pigments are used for ceramics, cosmetics, exterior wall paintings, and road pavements. ,, Besides the mineral and chemical pathways of synthesizing iron oxides, the bioderived onesbiogenic iron oxide (BIOX)are considered promising raw materials for highly thermostable inorganic red pigments. , Interestingly, the BIOXs can have different morphologies such as: (i) unique microtubular sheath with high porousness, (ii) organic–inorganic hybrid construct composed mainly of primary nanoparticles of amorphous ferric oxyhydroxides, or (iii) nanocomposite structures formed by sintering. , Recent studies have shown that the chemical compositions of the cultured BIOX (cBIOX) sheaths are modifiable by biotemplate techniques using isolated iron bacterial strains. , Moreover, the additive elements deposited on the BIOX sheaths could readily improve the color tones in heated products, indicating that the BIOXs are easily tunable materials . Herein, we describe new orange-hued iron oxide pigments with readily modifiable hues by changing the elemental composition in the BIOXs.…”

Study of biogenic iron oxyhydroxide for application in electronics and biotechnology

“…The need for reliable information on the structural and functional characteristics of nanosized materials produced by Leptothrix bacteria has grown in recent years [1][2][3]. The microaerophilic iron-oxidizing βproteobacteria from the genus Leptothrix are of great interest because during their growth they produce extracellular formations containing iron oxides and oxyhydroxides.…”