FG Biotechnologie der Wasseraufbereitung
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- FG Biotechnologie der Wasseraufbereitung (162)
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Synergistic enhancement of PFOA and 6:2-FTAB photodegradation using Au/Y-doped TiO₂ nanocatalysts
(2026)
Efficient degradation of perfluoroalkyl substances (PFAS) requires photocatalysts capable of promoting strong C-F bond cleavage and selective interfacial charge transfer. In this proof-of-concept-study, a dual-doped TiO2 nanophotocatalyst (Au2/Y5/P25) was synthesized by combining gold (Au) nanoparticles and yttrium (Y) dopants to enhance charge separation and reactive oxygen species (ROS) generation. Structural characterization supported Au deposition on the TiO2 surface and Y incorporation into the lattice, accompanied by a slight band-gap narrowing. Under UV irradiation in aqueous solution (unbuffered pH 5.8, room temperature) the nanophotocatalyst exhibited distinct degradation pathways for 1000 µg L−1 of two representative PFAS, perfluorooctanoic acid (PFOA) and Capstone B (6:2 FTAB), reflecting environmentally prevalent groups. PFOA underwent 99 % degradation within 100 min via a stepwise CF2-cleavage mechanism, generating a sequence of perfluorocarboxylic acids down to perfluorobutanoic acid (PFBA), consistent with enhanced electron-hole separation. In contrast, Capstone B showed rapid, single-step S-N bond cleavage to 6:2 perfluorooctanesulfonic acid (6:2 PFOS), primarily driven by hole- and •OH-mediated oxidation under oxygen-rich conditions. This process achieved 96 % degradation within 20 min but did not proceed to further defluorination, indicating oxidative limitations. Dissolved oxygen analysis revealed efficient electron utilization and sustained oxidative turnover without excessive oxygen depletion. The findings demonstrate that Au/Y co-doping promotes selective PFAS activation, enabling rapid precursor oxidation while exposing the kinetic limits of secondary C-F bond cleavage. These discoveries offer new insights into the design of plasmonic-rare-earth-modified TiO2 photocatalysts for efficient PFAS degradation through interface-driven oxidation pathways.
Biofouling remains a critical challenge in membrane bioreactors (MBR), which is primarily caused by the production of extracellular polymeric substances (EPS) as an initial step in biofilm formation. This still limits their widespread application in wastewater treatment. In the past decades, much research has been carried out to understand and consequently reduce biofouling in MBR. More recent studies have focused primarily on inhibiting the release of EPS by applying quorum quenching (QQ) to control biofouling in MBR. This study presents the first investigation of the QQ potential of Rubellimicrobium mesophilum and its effects on biofilm inhibition by EPS reduction, which is demonstrated for MBR operated with submerged flat sheet (PTFE, PS) and hollow fibre polyvinylidene fluoride (PVDF) membranes operated in parallel for 114 days. The QQ effect has a significant impact on the reduction in biofilm thickness on PTFE membranes by 45% and on PS membranes by about 47%, respectively. Additionally, the performance of PVDF was improved by 287.5%. Similarly, the total protein concentration on the PTFE membranes was reduced by 57%, while on the PS membranes, the reduction was 78%. In mixed liquor, protein reduction was 55%, indicating its effectiveness in controlling biofouling over extended operation. The biofilm formation was monitored by measuring the biofilm thickness via fluorescence microscopy and by analyzing the protein and sugar content of the developing biofilm and of the mixed liquor. All parameters indicated decreasing biofilm formation with increasing amounts of entrapped QQ bacteria, while the removal efficiency of organic compounds and ammonia remained similar between all MBRs.
Perfluorooctanoic acid (PFOA), a persistent environmental pollutant, poses significant health and ecological risks. Thisstudy investigates for the first time the photocatalytic degradation of PFOA using novel doped perovskite catalysts underpolychromatic UV–VIS irradiation with a peak emission at 366 nm. A series of nickel- and lanthanide-doped perovskites(NiMn2 O 4 , LaMnO 3 , NdMnO 3 , and their nickel-doped variants) were synthesized via a facile co-precipitation techniqueand characterized using X-ray diffraction (XRD), UV–VIS diffuse reflectance spectroscopy (UV–VIS-DRS), scanning elec-tron microscopy with energy-dispersive X-ray spectroscopy (SEM–EDX), N2 -physisorption, and microwave plasma atomicemission spectroscopy (MP-AES). Photocatalytic experiments revealed that Ni/NdMnO3 exhibited the highest degradationefficiency toward PFOA, likely due to its small band gap energy of 1.5 eV, facilitating efficient C–C bond cleavage.
In this study, we investigated the impact of varying iron (Fe) and aluminum (Al) contents on the adsorption of phosphonates to activated sludge. Phosphonates originating from household applications account for up to 40% of the non-reactive dissolved phosphorus in domestic sewage treatment plants and thus can contribute to the eutrophication of water bodies. Although these substances are not readily degradable, substantial quantities, ranging from 40% to more than 90%, are removed by sludge adsorption. The results demonstrate a strong correlation between the adsorption of aminophosphonates and the Fe3+ content of the sludge. The maximum phosphonate loadings were 5.94 mmol g−1 Fe3+ for ATMP, 4.94 mmol g−1 Fe3+ for EDTMP, 4.74 mmol g−1 Fe3+ for DTPMP, and 2.25 mmol g−1 Fe3+ for glyphosate. In contrast to pure ferric hydride flocs, the adsorption of phosphonates was approximately threefold higher when the hydroxides were located within activated sludge flocs. It is concluded that native sludge flocs provide larger iron surfaces than ferric hydroxide alone. Based on the weight of the adsorbents, aluminum salts were four times less efficient than ferric salts. In sludge without ferric or aluminum hydroxides, phosphonate adsorption was negligible.
Since the early 1980s, industrially relevant phosphonic acids have become established in a variety of industrial applications. This is largely due to their unique and advantageous characteristics and their scope of applications is still evolving. It is widely acknowledged that phosphonates are commonly used as complexing agents in detergents, including those employed for laundry and dishwashing. The most commonly utilized aminophosphonates include aminotris(methylenephosphonic acid) (ATMP), ethylenediaminetetra(methylenephosphonic acid) (EDTMP) and diethylenetriamine penta(methylenephosphonic acid) (DTPMP), in addition to organophosphonates such as hydroxyethylidene(diphosphonic acid) (HEDP) and 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC). The latter are primarily employed in the manufacture of industrial detergents or frequently used as components of industrial cleaning products. The elevated demand has prompted a discourse surrounding the prospective environmental consequences and the yet undetermined degradation pathways. The latest research data give rise to concerns regarding the continuous enrichment of industrially relevant phosphonates in the aquatic environment. It is thought that the impact of phosphonate penetration affects ecosystems in the aquatic environment. It is assumed that photochemical degradation, in particular, represents the principal pathway for the breakdown of phosphonates. Recently, evidence has emerged suggesting that biological degradation of these compounds may also represent a significant pathway. This chapter provides an overview of recent developments and highlights key findings in the abiotic and biotic degradation of industrially relevant phosphonates.
Decentralized solar water disinfection systems (DSODIS) in continuous flow systems are alternatives for large-scale improved water access in rural contexts. However, DSODIS in rural Ghana are limited. An exploratory sequential mixed-methods design was used to explore the enablers of and barriers to, as well as reported barrier perceptions to, the effective implementation of DSODIS in the Sawla-Tuna-Kalba (STK) District of Ghana. The qualitative data (26 respondents) were analyzed thematically, and the quantitative data (1155 household heads) were subjected to Poisson regression analyses. Enablers were categorized into themes such as willingness to pay for DSODIS, household and community participation, and willingness to use water from DSODIS. Similarly, the barriers include environmental barriers, technological barriers, economic barriers, and political and legal barriers. Household characteristics such as main water source and income, age group, education, marital status, household size, being born in the community, and years living in the community are statistically associated with reported barrier perceptions. Households with unimproved water sources and high income (IRR = 1.432, p = 0.000) and improved water sources and high income (IRR = 1.295, p = 0.000) are 43% and 30% more likely, respectively, to report more barrier perceptions compared with households with unimproved water sources and low income. Females (IRR = 1.070, p = 0.032) are marginally more likely to report more barrier perceptions compared with males. The model output also indicates that household heads with higher educational attainment (IRR = 1.152, p = 0.001) are 15% more likely to report more barrier perceptions compared with those with no formal education. These findings provide valuable information for policymakers and stakeholders aiming to provide quality water in rural Ghana where centralized systems cannot be installed.
The use of ultraviolet (UV) for water disinfection is known for its chemical-free process and with no harmful disinfection by-products. Yet, the disinfection process remains time-consuming, and many studies are limited to disinfection of one or two microbial species. Direct photolytic and glass-embedded TiO2 photocatalytic disinfection of four different bacterial species (Staphylococcus aureus, Salmonella senftenberg, Bacillus subtilis, and Escherichia coli) were assessed using UV-LED radiation with wavelengths of 365 nm. The optimization of the UV disinfection under different masses of the TiO2 photocatalyst was evaluated. Additionally, the order of disinfection of the different bacteria species was assessed. The disinfection effects were measured based on the potential to reduce the number of bacteria species, calculated in colony-forming units/mL and log reduction units. The disinfection of Staphylococcus aureus was enhanced from 1.46 log reduction units in the UV-alone treatment to a high of 5.65 log reduction units in the UV + 0.08 g TiO2 treatment. Regarding Salmonella senftenberg, disinfection was enhanced from 1.26 log reduction units to 3.85 log reduction units in UV-alone experimental treatments and UV + 0.04 g TiO2, respectively. Similarly, an increase in Bacillus subtilis reduction was achieved from a low of 0.69 log reduction units to a high of 2.98 log reduction units in UV-alone treatments and UV + 0.08 g TiO2, respectively. The disinfection of Escherichia coli was enhanced from 2.49 log reduction units (UV-alone treatment) to a high of 6.35 log reduction units (UV + 0.02 g TiO2). The findings provide key implications and new insights into the studied bacteria species and the future application of porous glass-embedded TiO2 photocatalysts to enhance bacteria disinfection using UV light for improved water.
The antimicrobial properties of silver are well-known and widely applied. Although it is known, that silver interacts and binds on complex organic substances like proteins, many experiments on the sterilisation efficiency and inhibiting properties are still carried out in complex culture media. Given, that silver is often applied in environments with no or few organic substrates, like cooling circuits or in the treatment of tap and process water, further insight on the minimum inhibition concentration and lethal concentration at those conditions is of interest. We have developed a defined medium for the standard bacterium Pseudomonas aeruginosa that is free of complex organic carbon with equal cultivation properties like commonly used nutrient solutions. With this medium we could narrow the range of the MIC between 2.5 μg to 10 μg∙L−1, which very much overlaps with the bactericidic concentration depending on the initial concentration of bacteria cells. These results might help to optimise the technical application of silver. We further observed a delayed growth of bacterial cultures of up to three days compared to silver free controls, which is caused either by a partial sterilisation down to theoretical one surviving cell or by a prolonged lag phase. Based on these observations we recommend a prolonged incubation for experiments on sterilisation with silver and the use of defined media, which do not interact with the disinfecting agent.
This study presents the photocatalytic degradation of the aminophosphonate ethylenediaminetetra(methylenephosphonic acid) (EDTMP) with a range of different doped nanoparticles (NP). The photocatalysts were based on TiO2 benchmark P25 and gold (Au) doped either with sodium (Na), potassium (K) or yttrium (Y). The synthesized photocatalysts were characterized via TEM, XRF, XRD, UV-DRS (band gap estimation) and N2-physisorption. Photocatalytic pre-screening at pH values of 3, 7 and 10 indicated highest o-PO4 release of EDTMP at pH 7 and 10 for NP either doped with K or Y. The results of LC/MS analysis showed that the NPs doped with 5 % Y (Au2/Y5/P25) resulted in the fastest degradation of EDTMP. The target compound was completely degraded within 60 min, 4 times faster than photochemical treatment of unadulterated EDTMP. Importantly, also the transformation products were accelerated by the photocatalytic treatment with Au2/P25 either doped with 5 % Y or 10 % K. The results of scavenger experiments indicated that the enhanced photocatalytic degradation of EDTMP is primarily attributable to the presence of hydroxyl radicals in the bulk and to a lesser extent to •O2− and electron-holes (h+) at the surface of the catalysts. The study demonstrates that the catalytic efficiency of TiO2 nanocomposites is significantly influenced by the choice of dopants, which affect particle size, band gap, and photocatalytic activity. Yttrium at low concentrations (i.e., 5 wt% Y) doping emerged as particularly effective, enhancing both the visible light absorption and h+ separation, leading to superior photocatalytic performance in the degradation of EDTMP. The Au content also plays a crucial role in enhancing the photocatalytic efficiency. However, the combination of Au and Na doping was found to be less effective for this photocatalysis in aqueous media, potentially due to larger particle sizes and insufficient dopant contents. In conclusion, the findings emphasise the necessity of optimising both the selection of dopants and the design of catalysts in order to enhance photocatalytic applications.
The UV treatment of 6:2 FTAB involves the mitigation of this persistent chemical by the impact of ultraviolet radiation, which is known for its resistance to environmental breakdown. UV treatment of PFOA and/or 6:2 FTAB, and the role of responsible species and their mechanism have been presented. Our investigation focused on the degradation of perfluorooctanoic acid (PFOA) and 6:2 fluorotelomer sulfonamide alkyl betaine (6:2 FTAB, Capstone B), using UV photolysis under various pH conditions. Initially, we used PFOA as a reference, finding a 90% decomposition after 360 min at the original (unadjusted) pH 5.6, with a decomposition rate constant of (1.08 ± 0.30) × 10−4 sec−1 and a half-life of 107 ± 2 min. At pH 4 and 7, degradation averaged 85% and 80%, respectively, while at pH 10, it reduced to 57%. For 6:2 FTAB at its natural pH 6.5, almost complete decomposition occurred. The primary UV transformation product was identified as 6:2 fluorotelomer sulfonic acid (6:2 FTSA), occasionally accompanied by shorter-chain perfluoroalkyl acids (PFAAs) including PFHpA, PFHxA, and PFPeA. Interestingly, the overall decomposition percentages were unaffected by pH for 6:2 FTAB, though pH influenced rate constants and half-lives. In PFOA degradation, direct photolysis and reaction with hydrated electrons were presumed mechanisms, excluding the involvement of hydroxyl radicals. The role of superoxide radicals remains uncertain. For 6:2 FTAB, both direct and indirect photolysis were observed, with potential involvement of hydroxyl, superoxide radicals, and/or other reactive oxygen species (ROS). Clarification is needed regarding the role of 𝑒−𝑎𝑞 in the degradation of 6:2 FTAB.
