Abstract

In this study, we attempted to synthesize Fe-type layered double hydroxide (LDH) from biomass combustion ash for phosphorus removal.<br />In Japan, biomass power generation is being promoted for effective biomass utilization, and there is a big problem that a large amount of biomass combustion ash is discharged to dispose at landfill as industrial wastes. On the other hand, water pollution caused by anions, such as eutrophication with phosphoric acid (PO4 ^3-) in wastewater, has become a problem. As a simple treatment method, adsorption method using anion removal material is focused. In the adsorption method, it is important to select the adsorbent, and Fe-based LDH are expected as phosphorus-removing materials.<br />In this experiment, the combustion ash was added to HCl to dissolve divalent cations, Ca and Mg, in the ash, iron chloride hexahydrate (FeCl₃·6H₂O) was added to prepare acidic liquid mixture with a molar ratio of (Ca + Mg)/Fe = 2 - 3, and the mixture stirred to synthesize the product including LDH at 40 ^oC for 6 h with keeping pH 12.5. The product was analyzed by scanning electron microscope (SEM), energy dispersive X-ray spectrometer (EDS) and powder X-ray diffraction (XRD), and the phosphorus removal ability of the product was investigated.<br />As the result, Ca-Mg-Fe LDH was successfully synthesized from biomass combustion ash with addition of FeCl₃, and the obtained product showed high phosphorus removal ability. From Langmuir and Freundlich adsorption models to estimate the phosphorus adsorption of the product, Langmuir equation could be more realistic than the Freundlich’s equation.