Physico-chemical properties of palm oil fuel ash as composite sorbent in kaolin clay landfill liner system

Abstract

This paper presents the physico-chemical properties of palm oil fuel ash (POFA) a biomass residue, while justifying its use as composite sorbent when admixed with kaolin clay, for the purpose of designing composite sanitary landfill liner. Laboratory analysis conducted centered on properties of sundried raw POFA passing through 150µ, 75µ, 38µ test sieves, and of the fine ground ash to 27µ , after mechanical homogenization of retained ashes. Physical analysis conducted includes particle size distribution and density tests for blended ash. Chemical tests include Energy Dispersive X-Ray Analysis (EDX), for elemental compositions, with particular interest in exchangeable metal cations and background concentration of selected toxic heavy metals. Tests also include X-ray Fluorescence (XRF), for bulk chemical components, specific surface area(SSA), from Particle size analyzer (PSA), scanned electron microscope(SEM), for morphological structure of retained and ground ash samples, mass loss on ignition (LOI), at 440 ± 25 °C, for a period of 4 h. Primary factors affecting variable charge ions at edges of kaolin clay is pH, thus, was also determined as hydrogen ion concentration in POFA-aqueous environment. Material sourcing and pretreatment technology were reported. Silica oxide (SiO2), present in ground ash via XRF was found to be 53.20%, while summation of SiO2, Al2O3, and Fe2O3 present was 69.80%. Inherited calcium oxide (CaO-lime) was 9.73%. Exchangeable cations present are Na2+, K2+, Ca2+ and Mg2+. Structural and appearance analysis shows that ground POFA was amorphous. From these properties inferences were drawn on expected chemical reactions from POFA, and when both materials are blended for the design of composite sanitary landfill liner. This novel material is hoped to provide a more efficient trapping mechanism of toxic heavy metals ions in leachate, when compared with single liner material from kaolin clay. Conclusively, POFA a bio-sorbent could be suitably used as composite sorbent for improvement of kaolin clay designed as component of engineered sanitary landfill liner.