Synthesis of birnessite-type manganese oxide from two different reducing agents via solvent-free method and the catalytic activity in degradation of POME

Abstract

Birnessite-type manganese oxide is multifunction material that has been used in various application and the characteristic depends heavily upon its preparation method. In this study, birnessite-type manganese oxide was synthesized using the reaction between KMnO4 (oxidant) and two different reducing agents i.e., citric acid and oxalic acid via a solvent-free method. The characterization of the birnessite was carried out using X-Ray Diffraction (XRD), Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy (SEM-EDX), and Surface Area Analyzer (SAA). Birnessite from this variation of reducing agents showed different levels of crystallinity, diverse morphology, crystal size, and surface area. The birnessite-type was then applied as a catalyst for the degradation of Palm Oil Mill Effluent (POME) with hydrogen peroxide (H2O2) as an oxidant to reduce the concentrations of Chemical Oxygen Demand (COD). The maximum reduction in COD concentration was obtained using the catalyst concentration of 400 and 800 mg/L for reducing agent of as-synthesized catalyst citric acid and oxalic acid. Birnessite-type manganese oxide shows potential as a catalyst in the degradation of POME with citric acid as reducing agents showed better degradation in reducing COD values.

Preliminary Study on COD Removal on the Treatment of Palm Oil Mill Effluent (POME) Using Birnessite-Type Manganese Oxide via a Solvent-Free Method

“…From the image, it was revealed that the δ-MnO2 particles obtained in this work consist of aggregate particles with more irregular sizes compared to birnessite that was calcined at 700 o C for 7 hours [5]. This morphology with irregular sizes is also generated from using organic acid as a reducing agent via a solvent-free method [9].…”

“…The previous study reported that the COD removal relied upon the precursor used for the synthesis of manganese oxide. The use of citric acid for the synthesis of manganese oxide produced 61% of COD removal, whereas oxalic acid precursor for the synthesis of manganese oxide resulted in 56% of COD removal, respectively [9]. It is evident that the different textural properties (table 1) of the manganese oxides used as Fenton catalyst play a key role in the COD removal of the POME.…”

“…These radicals with strong oxidizing power will attack, react non-selectively and decompose most organic contaminants into oxidized compounds such as carbon dioxide and water. Our previous report indicated that the birnessite-type manganese oxides synthesized from MnO4‾ reduction using the two organic acids (citric and oxalic acid as reducing agents) showed promising heterogeneous Fenton catalyst in the degradation of palm oil mill effluent (POME) [9]. It was revealed that the catalytic performance of the MnO2 materials strongly depends on their structural properties, which is in turn precursor-dependence.…”