Improved phosphoric acid recovery from sewage sludge ash using layer-by-layer modified membranes
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Publication date
01.10.2019
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01A - Journal article
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Journal of Membrane Science
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587
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Elsevier
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Abstract
We report an advanced treatment method for phosphoric acid recovery from leached sewage sludge ash. Layer-by-layer (LbL) polyelectrolyte deposition has been used as a tool to modify and convert a hollow ultrafiltration membrane into a nanofiltration (NF) LbL membrane for H3PO4 recovery. To build the LbL membrane, poly(styrenesulfonate) PSS was chosen as polyanion, while three different polycations were used: a permanently charged polyelectrolyte, poly(diallyldimethylammonium chloride), PDADMAC; a pH-dependent charged polyelectrolyte poly(allylamine hydrochloride), PAH; and a PAH modified with guanidinium groups (PAH-Gu). Based on detailed surface characterizations (AFM, XPS and Zeta-potential) it was concluded that both charge density and pH-responsiveness of the polycations are key parameters to control the final membrane surface structure and transport properties. The surface properties of LbL-coated membranes were correlated with the membrane filtration performance, when exposed to the real leached sewage sludge ash solution. The highest permeability was recorded for (PDADMAC/PSS)6, a result that was rationalized on its loose, and possibly less interpenetrated, structure, followed by (PAH-Gu/PSS)6 characterized by a more dense, compact layer. H3PO4 recovery was the highest in the case of (PDADMAC/PSS)6, but the retention of multivalent metals (Fe3+ and Mg2+) was low, leading to a more contaminated permeate. The opposite trend was observed for (PAH-Gu/PSS)6, resulting in a less metal-contaminated, but also a less H3PO4-concentrated permeate. Our LbL-modified membranes were found to improve the permeability and H3PO4 recovery compared to a commercially available acid-resistant NF membrane.
Keywords
Layer-by-layer, Polyelectrolyte, Phosphate recovery, Sewage sludge ash, Water treatment
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ISBN
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1873-3123
0376-7388
0376-7388
Language
English
Created during FHNW affiliation
Yes
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Published
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Citation
Paltrinieri, L., Remmen, K., Müller, B., Köser, J., & Wintgens, T. (2019). Improved phosphoric acid recovery from sewage sludge ash using layer-by-layer modified membranes. Journal of Membrane Science, 587. https://doi.org/10.1016/j.memsci.2019.06.002