Utilization of quaternary ammonium-cation-modified birnessite-type manganese oxide (OL-1) as sorbent of organic pollutants

• Main Author: Fulgencio, Fegilyn C.
• Format: text
• Language: English
• Published: Animo Repository 2003
• Subjects: Pollutants; Manganese oxides; Sorbents; Gases > Absorption and adsorption; Chemistry
• Online Access: https://animorepository.dlsu.edu.ph/etd_masteral/3115
• Institution: De La Salle University

The study focused on the evaluation of the efficacy of quaternary ammonium cation (QAC) - modified birnessite-type material as sorbent of organic pollutants by Gas Chromatography (GC) using solid phase microextraction (SPME) technique. Birnessite-type manganese oxide was synthesized by the oxidation of Mn(OH)2 by KMnO4/MgCl2. The structure of this octahedral layered manganese oxide (OL-1) was verified by Powder X-ray Diffraction (XRD). An interlayer spacing of approximately 10 A was observed which is one of the diagnostic peaks of buserite-type material, the hydrated form of birnessite-type manganese oxide. The cation-exchange capacity (CEC) of this material after ion-exchanged with Mg2+ ions and tetramethylammonium cation (TMA+) as determined by Atomic Absorption Spectroscopy (AAS) reached as high as 24.78 meq/100 g OL-1 and 140.66 meq/100 g OL-1, respectively. The Na-OL-1 was then modified with varying concentrations of TMA+ and HDTMA+ (hexadecyltrimethylannonium cation) surfactants. The XRD profiles of TMA-OL-1 and HDTMA-OL-1 show a topotactic ion-exchange reaction. Fourier Transform Infrared Spectroscopy (FT-IR) provided evidence on the incorporation of TMA+ and HDTMA+ into the birnessite-type framework. Further characterization of OL-1 and its modified counterparts by Scanning Electron Microscopy/Electron Dispersive X-ray (SEM/EDX) and Differential Thermal Analysis (DTA) was done. To evaluate the performance of the materials as sorbents of organic pollutants, 1,2,4-trichlorobenzene (TCB) in 10 percent aqueous methanol was allowed to equilibrate with Na-OL-1 and QAC-modified OL-1 for 2 hours. The amount of 1,2,4-TCB sorbed on these sorbents was extracted by headspace solid phase microextraction (SPME) and quantitatively determined by GC using standard calibration method. Sorption capacity of OL-1 and QAC-modified-OL-1 was evaluated based on sorption partition coefficient, Kd of TCB. The obtained Kd values revealed the appreciable sorption capacity of OL-1. Higher Kd values were obtained for the QAC-modified materials, exemplifying enhanced sorption capacity of these modified materials. The uptake of TCB by TMA-OL-1 was however higher than that of HDTMA-OL-1.