Optimising the synthesis of Birnessite

Author: Faisal Bin Hudayb

Bin Hudayb, Faisal, 2017 Optimising the synthesis of Birnessite, Flinders University, School of Chemical and Physical Sciences

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Abstract

Experiments presented in this thesis explore different methods for the synthesis of birnessite with the aim of increasing the crystallite size of the resulting material. Birnessite was synthesized by reducing an alkaline solution of KMnO4 with MnCl2 (aq). Following this general method, various factors such as the nature of the base used, reaction temperature, the influence of pH, effect of recrystallisation with KCl, order of addition of the solutions, the rate of addition of MnCl2 and influence of the reagent concentration were investigated. Powder XRD and SEM techniques were used to monitor the purity and particle or crystallite size of the resulting birnessite. The molar ratio of MnO4-/Mn2+ of 0.22 was found to be the optimum ratio for synthesizing crystalline birnessite and NaOH rather than KOH was found to improve crystallite size. Room temperature and a higher value of pH, around 14.7, were found to favour synthesis of crystalline birnessite. Finally, the flow rate for the addition of MnCl2 solution to KMnO4 solution was optimized at a value of 0.22 ml min-1.

Keywords: birnessite, hausmannite
Subject: Nanotechnology thesis

Thesis type: Masters
Completed: 2017
School: School of Chemical and Physical Sciences
Supervisor: Allan Pring