Using biomass fly ashes for the removal of phosphorus from a synthetic wastewater

The main goal of the present work was to study the removal of Phosphorus (P) from a synthetic wastewater (SWW) by using a biomass fly ash as the adsorbent agent in an up-flow fixed-bed column. The fly ash was produced in a biomass power plant that uses a bubbling fluidized bed combustor. Three different Contact Times with Ashes (CTA) were tested in the assay 1: 2, 8 and 16 min. In this assay, a P initial concentration in the SWW of 18 mg P/L and a fly ash mass of 4.525 g were used for each CTA. P-removal percentages of 76.7%, 84.63% and 89.22%, for a Liquid/Solid (L/S) ratio of 0.1 L/g were determined for the CTA values of 2, 8 and 16 min, respectively. A linear decrease in the removal efficiency of P was registered with the increase of the L/S ratio. In the assay 2, three different initial concentrations of P in the SWW were tested: 10, 20 and 40 mg P/L. In this assay, a CTA of 8 min and a fly ash mass of 6.670 g were used for each initial concentration of P. P-removal percentages of 98.8%, 86.6% e 80.8%, for a L/S ratio of 0.1 L/g were determined for the P initial concentrations of 10, 20 and 40 mg P/L, respectively. A linear decrease in the removal efficiency of P was observed with the increase of L/S ratio. The experimental data was modeled according to the isotherms of Langmuir and Freundlich. High determination coefficients (R2) were obtained. The adsorption coefficients (Qmax) of P in fly ash were of 3.96, 5.70 and 8.58 mg P/g fly ash for CTA values of 2, 8 and 16 min, respectively, and of 5.82, 6.46 and 22.9 mg P/g fly ash for the P initial concentrations of 10, 20 and 40 mg P/L, respectively.