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A Synthesized Manganese Oxide for Easily Making Durable Manganese‐Coated IRIS Tubes
Author(s) -
Rabenhorst Martin C.,
Persing Kristine A.
Publication year - 2017
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj2016.10.0348n
Subject(s) - birnessite , coating , materials science , oxide , durability , manganese , iris (biosensor) , centrifuge , chemical engineering , composite material , metallurgy , computer science , manganese oxide , physics , computer security , nuclear physics , biometrics , engineering
Core Ideas We developed a new synthesis of well‐crystalline birnessite for making Mn‐coated IRIS tubes. The Mn coating can be easily and quickly applied using a foam brush and lathe. The Mn coating on PVC tubes has strong adhesion and good durability. Up to 30 (50‐cm) Mn‐coated IRIS tubes can be manufactured per hour. The speed and ease of manufacturing permits broader use of Mn‐coated IRIS tubes. During the last decade, Indicator of Reduction in Soils (IRIS) technology has been developed whereby polyvinyl chloride (PVC) devices coated with an Fe‐oxide paint are inserted into the soil to document strongly reducing conditions. The IRIS devices are easy to use and interpret, are less prone to difficulties associated with other methods of assessing reducing soil conditions, and have been endorsed by the National Technical Committee for Hydric Soils. There has been longstanding interest in Mn‐oxide‐coated tubes, but until lately there have been insurmountable problems associated with poor adhesion and durability of the Mn‐oxide coating. Recently, workers have suggested an easily synthesized, poorly crystalline birnessite to make Mn‐coated PVC IRIS devices, but their manufacturing procedure for tubes with a durable Mn coating is cumbersome and time consuming. We have developed an easily synthesized crystalline birnessite paint that can be used to quickly make IRIS tubes with a strongly adhering and durable Mn‐oxide coating. The procedure requires a large excess of sodium lactate to reduce KMnO 4 quickly, followed by centrifuge washing and 3 d of dialysis. Once adjusted to the proper consistency, the birnessite can be painted onto PVC tubing using a foam brush and a lathe‐type device, such that approximately 30 tubes can be prepared in as little as 1 h. Preliminary testing conformed with other investigations suggesting that Mn‐oxide coatings become solubilized and stripped from tubes more rapidly, and under less strongly reducing conditions, than the Fe‐oxide‐coated tubes.