Wintgens, Thomas

Wintgens, Thomas


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  • Publikation
    Improved phosphoric acid recovery from sewage sludge ash using layer-by-layer modified membranes
    (Elsevier, 01.10.2019) Paltrinieri, Laura; Remmen, Kirsten; Müller, Barbara; Köser, Joachim; Wintgens, Thomas [in: Journal of Membrane Science]
    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.
    01A - Beitrag in wissenschaftlicher Zeitschrift
  • Publikation
    Phosphorus recovery in an acidic environment using layer-by-layer modified membranes
    (Elsevier, 15.07.2019) Remmen, Kirsten; Müller, Barbara; Köser, Joachim; Wintgens, Thomas [in: Journal of Membrane Science]
    Phosphorus (P) is a limited natural resource and essential for global food supply, particularly given our ever-growing world population. However, natural P deposits are restricted to just a few countries and the quality of exploited primary sources is declining. Phosphorus recovery from sewage sludge or sewage sludge ash leached by acids is hence gaining importance. During P recovery the removal of impurities is a challenge that can be addressed by nanofiltration retaining e. g. multivalent metals and allowing phosphoric acid to pass. However, currently available membranes show low permeability and limit this process option economically. Layer-by-layer (LbL) membrane synthesis is a technology that allows membrane performance to be tailored to individual filtration tasks. Little is known for such membranes with respect to acid resistance, acid permeability and impurity rejection. We show that LBL membranes based on PDADMAC/PSS show the desired passage of phosphoric acid with retentions values below 10%, aluminum retention was always above 95%. Permeabilities up to 4 L/(m2 h bar) were reached even up to a phosphorous recovery of 75%. Overall permeabilities were 16 times higher than a commercial benchmark membrane. Initial stability tests and upscaling into a larger module show the viability of the proposed modification approach.
    01A - Beitrag in wissenschaftlicher Zeitschrift
  • Publikation
    Layer-by-layer membrane modification allows scandium recovery by nanofiltration
    (Royal Society of Chemistry, 07/2019) Remmen, Kirsten; Lenz, Markus; Hedwig, Sebastian; Wintgens, Thomas [in: Environmental Science. Water, Research & Technology]
    Aluminium scandium (Sc) alloys are stronger, more corrosion resistant and more heat tolerant than classical aluminium alloys and allow for 3D printing. In particular, the aerospace industry benefits from better fuel efficiency due to lighter materials as well as the advantages of additive manufacturing. However, Sc is currently not available in sufficient quantities and has recently been identified as a raw material critical to the economy. Due to the recentness of the demand, technologies for recovery of Sc from secondary sources are in their infancy. In this study, Sc recovery from titanium dioxide pigment production waste by nanofiltration was investigated. Custom-made layer-by-layer (LbL) modified membranes were optimized with regards to their elemental retention (i.e., selectivity towards Sc) as well as their acid resistance. In model solutions, the optimized membrane retained up to 64% ± 4% Sc, removing the major impurity, iron (Fe), efficiently (12% ± 7% retention) while achieving high flux [32 L m−2 h−1] at a low transmembrane pressure of 5 bar. Acid resistance was shown down to a pH of 0.1, which could be even further increased (up to ≤3 M HCl) by adding more bi-layers and changing the coating conditions. In real wastes, the optimized LbL membrane showed higher Sc retention (60% vs. 50%) compared to a commercial acid resistant membrane, while achieving considerably higher fluxes [27 L m−2 h−1 versus 1 L m−2 h−1, respectively at 5 bar]. It was possible to operate filtration at low transmembrane pressure with up to 70% permeate recovery and flux that was still high [∼10 L m−2 h−1]. In a nutshell, titanium dioxide pigment wastes contained sufficient amounts to satisfy the growing demand for Sc and can be exploited to their full extent by LbL nanofiltration due to the proven advantages of acid stability, Sc retention and selectivity and high achievable fluxes at low pressures.
    01A - Beitrag in wissenschaftlicher Zeitschrift
  • Publikation
    Phosphorus recovery potential in Sofia WWTP in view of the national sludge management strategy
    (Elsevier, 01/2017) Ribarova, Irina; Dimitrova, Sonja; Lambeva, Ralitsa; Wintgens, Thomas; Stemann, Jan; Remmen, Kirsten [in: Resources, Conservation and Recycling]
    In view of the vital importance of phosphorus and its increasing scarcity as a natural resource, phosphorus recovery has recently gained significant scientific and technical interest. The aim of this study is to support the implementation of the Bulgarian national sludge management strategy, particularly its objective to achieve more efficient resource management of phosphorus in waste water treatment plants (WWTPs). The study estimates the potential for phosphorus recovery from the municipal WWTP at Sofia, the largest in Bulgaria, serving some 14% of the Bulgarian population. The phosphorus content of five process streams (thickener supernatant, dewatering centrate, sludge before digestion, sludge after digestion and ash) is analysed on the basis of one year of measurements. It is estimated that 170–250 t phosphorus could be recovered annually from the WWTP from digested sludge or ash, depending on the phosphorus recovery technology used.
    01A - Beitrag in wissenschaftlicher Zeitschrift