TITLE:
A new approach for reduction of methylene green withascorbic acid by de-oxygenation through carbondioxide
AUTHORS:
Rafia Azmat, Noshab Qamar, Raheela Naz
KEYWORDS:
Ascorbic Acid; Methylene Green; Sodium Carbonate; Charged Species; Secondary Reactions, Elevated Temperature
JOURNAL NAME:
Natural Science,
Vol.3 No.7,
July
27,
2011
ABSTRACT: Reduction kinetics of the methylene green (MG) with ascorbic acid (AA) in acidic medium at λmax 660 nm was monitored through visible spectrophotomtry in absence and presence of sodium carbonate. CO2 release through reaction of sodium carbonate and oxalic acid, created deoxygenated atmosphere for reduction of dye which greatly boosted the reaction rate. Initially slow reaction in presence of atmospheric oxygen proceeded rapidly when sodium carbonate was added. The reaction followed fractional order kinetics with AA and zero order kinetics with MG. The rate of reaction shows no linear dependence on [H+] concentration as an acidic medium. The rate of reaction is directly related with the elevated concentration of salt, which suggests that the two same charged species are involved in the rate determining step. Secondary reactions at elevated temperature showed complex kinetics.