Sorptive removal of phosphorus by flue gas desulfurization gypsum in batch and column systems

Authors: HAMID, A - Auburn University; WILSON, A - Auburn University; Torbert, Henry - Allen; WANG, D - Auburn University

Submitted to: Chemosphere
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/28/2023
Publication Date: 2/4/2023
Citation: Hamid, A., Wilson, A.E., Torbert III, H.A., Wang, D. 2023. Sorptive removal of phosphorus by flue gas desulfurization gypsum in batch and column systems. Chemosphere. 320:138062. https://doi.org/10.1016/j.chemosphere.2023.138062.
DOI: https://doi.org/10.1016/j.chemosphere.2023.138062

Interpretive Summary: Phosphorous (P) over-loading is always a central topic due to its strong linkage to harmful algal blooms (HABs) and its importance in wastewater treatment, fueling immediate remediation attempts to reduce P loading from point (e.g., wastewater) and nonpoint sources (e.g., P fertilizers). However, previous remediation techniques (e.g., filtration and algaecides) are proved expensive and difficult for large-scale applications. Flue gas desulfurization (FGD) gypsum, produced as an energy plant waste byproduct, is proposed as a physiochemical remediation strategy through P sorption , but limited research is available on the practical application of FGD gypsum to remove P from water. A study was conducted to investigate the sorptive removal efficiency of P by FGD gypsum under environmentally relevant P concentrations in a fixed-bed column experiments packed with FGD gypsum The fixed-bed column experimental results showed that sorption rate is directly proportional to the applied flow rate, irrespective of the tested P concentrations. Our findings can be extrapolated to evaluate the usability of FGD gypsum in removing P to mitigate HABs and P-loaded wastewater under the tested P concentrations.

Technical Abstract: Phosphorous (P) over-loading is always a central topic due to its strong linkage to harmful algal blooms (HABs) and its importance in wastewater treatment, fueling immediate remediation attempts to reduce P loading from point (e.g., wastewater) and nonpoint sources (e.g., P fertilizers). However, previous remediation techniques (e.g., filtration and algaecides) are proved expensive and difficult for large-scale applications. Flue gas desulfurization (FGD) gypsum, produced as an energy plant waste byproduct, is proposed as a physiochemical remediation strategy through P sorption. Limited research is available on the practical application of FGD gypsum to remove P from water. Herein, batch sorption experiments were performed to investigate the sorptive removal efficiency of P by FGD gypsum under environmentally relevant P concentrations (0.01 – 0.25 mM). Additionally, fixed-bed column experiments packed with FGD gypsum were performed using elevated P concentrations (0.1 – 1.0 mM) to understand the scalability of gypsum in practical applications. During batch sorption experiments, P sorption equilibrium was reached within 24 h that includes an initially fast step (via boundary layer diffusion), followed by a slow rate-determining step (via intraparticle diffusion). P sorption kinetics followed the pseudo second-order kinetics, indicating chemisorption. P sorption at equilibrium can be simulated by both the Freundlich and Langmuir sorption isotherms. The Langmuir sorption isotherm yields a maximum sorption capacity (Qmax) of 36.1 mM kg-1. The fixed-bed column experimental results showed that sorption rate is directly proportional to the applied flow rate, irrespective of the tested P concentrations. Our findings can be extrapolated to evaluate the usability of FGD gypsum in removing P to mitigate HABs and P-loaded wastewater under the tested P concentrations.