Fixed-bed column studies of phosphonate and phosphate adsorption on granular ferric hydroxide (GFH)

The use of phosphonates as antiscalants in membrane processes is common. Before they are discharged into the receiving water, they should be removed from the membrane concentrate to protect the aquatic environment. This study conducted fixed-bed column experiments on the adsorption of diethylenetria...

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Bibliographic Details
Published in:Process safety and environmental protection 2021-09, Vol.153, p.301-310
Main Authors: Reinhardt, Tobias, Rott, Eduard, Schneider, Philip A., Minke, Ralf, Schönberger, Harald
Format: Article
Language:English
Subjects:
Adsorption
Aquatic environment
Calcium compounds
Desorption
Electrical conductivity
Electrical resistivity
Ferric hydroxide
Fixed-bed column
Hydrochloric acid
Membrane processes
Membranes
Ortho-phosphate
pH control
pH effects
Phosphonates
Phosphonic acids
Precipitates
Receiving waters
Regeneration
Sodium hydroxide
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Summary:The use of phosphonates as antiscalants in membrane processes is common. Before they are discharged into the receiving water, they should be removed from the membrane concentrate to protect the aquatic environment. This study conducted fixed-bed column experiments on the adsorption of diethylenetriaminepenta(methylene phosphonic acid) (DTPMP) and ortho-phosphate on granular ferric (hydr)oxide (GFH). The objective was to investigate the adsorption and desorption performance using real membrane concentrate, while testing both the usability of the GFH and that of the regeneration solutions over multiple cycles. Whereas a synthetic solution with DTPMP allowed almost complete regeneration, the adsorption performance with real membrane concentrate at the original pH ≅ 8 decreased significantly. This could be attributed to the precipitation of calcium compounds which disturbed the adsorption/desorption process. With the introduction of a novel acidic regeneration step to remove the precipitates, an adsorption performance of 95% over 20 cycles was achieved. The hydrochloric acid (HCl) can be reused when its pH is kept constant by a pH control. The sodium hydroxide solution (NaOH) for alkaline regeneration can be reused several times. However, the desorption performance decreased significantly when its electrical conductivity dropped below 90 mS/cm. Replacing the NaOH regularly can significantly improve the desorption performance.
ISSN:0957-5820
1744-3598
DOI:10.1016/j.psep.2021.07.027