Phosphate sorption by three potential filter materials as assessed by isothermal titration calorimetry

• Published in: Journal of environmental management Vol. 143; pp. 26 - 33
• Main Authors: Lyngsie, Gry, Penn, Chad J., Hansen, Hans C.B., Borggaard, Ole K.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.10.2014; Elsevier; Academic Press Ltd
• Subjects: Adsorption; Agriculture; Animal, plant and microbial ecology; Applied ecology; Biological and medical sciences; Calcium Carbonate; Calcium phosphates; Calcium Phosphates - chemistry; Calorimetry - methods; CFH-12; Conservation, protection and management of environment and wildlife; Creeks & streams; Eutrophication; Fe-oxides; Ferrous Compounds - chemistry; Filtralite-P; Filtration - instrumentation; Filtration - methods; Fundamental and applied biological sciences. Psychology; General aspects; Hydrogen-Ion Concentration; Limestone; Oxides; P sorbing reactions; Phosphates; Phosphates - chemistry; Phosphorus - chemistry; Sorption; Limestone; Filtralite-P; CFH-12; P sorbing reactions; Fe-oxides; Calcium phosphates; Sorption; Calorimetry; Oxides; Calcium phosphate; Environmental management
• ISSN: 0301-4797; 1095-8630
• DOI: 10.1016/j.jenvman.2014.04.010

Phosphorus eutrophication of lakes and streams, coming from drained farmlands, is a serious problem in areas with intensive agriculture. Installation of phosphate (P) sorbing filters at drain outlets may be a solution. The aim of this study was to improve the understanding of reactions involved in P sorption by three commercial P sorbing materials, i.e. Ca/Mg oxide-based Filtralite-P, Fe oxide-based CFH-12 and Limestone in two particle sizes (2–1 mm and 1–0.5 mm), by means of isothermal titration calorimetry (ITC), sorption isotherms, sequential extractions and SEM-EDS. The results indicate that P retention by CFH is due to surface complexation by rapid formation of strong Fe–P bonds. In contrast, retention of P by Filtralite-P and Limestone strongly depends on pH and time and is interpreted due to formation of calcium phosphate precipitate(s). Consequently, CFH can unambiguously be recommended as P retention filter material in drain outlets, whereas the use of Filtralite-P and Limestone has certain (serious) limitations. Thus, Filtralite-P has high capacity to retain P but only at alkaline pH (pH ≥ 10) and P retention by Limestone requires long-time contact and a high ratio between sorbent and sorbate. [Display omitted] •The Fe oxide-based CFH is a highly efficient phosphate sorbent.•CFH rapidly forms strong Fe–P bonds on Fe oxide surfaces.•P retention by Limestone is slow and requires high sorbent:sorbate ratio.•P retention by Filtralite-P strongly depends on pH with high sorption at pH ≥ 10 but no sorption at pH ≤ 8.