MXenes are a family of two-dimensional materials made of layers of transition-metal carbides or nitrides, discovered relatively recently but already celebrated for their extraordinary surface area, electrical conductivity and tunable surface chemistry. Ti₃C₂Tₓ, the most studied member of the family, consists of stacked sheets of titanium carbide whose surfaces carry a mixture of terminal groups, denoted Tₓ, typically combinations of oxygen, hydroxyl and fluorine. Those surface groups make the material hydrophilic and give it a strong negative charge in water, both attractive qualities for membrane science. In principle, adding MXene nanosheets into a polymer membrane should create faster water channels, better selectivity and improved antifouling behavior, because water molecules glide along the charged, oxygen-rich surfaces far more readily than they pass through the dense polymer itself.

In practice, however, MXene has a fatal weakness in aqueous environments. The same surface chemistry that makes it hydrophilic also makes it vulnerable to oxidation: over time, water and dissolved oxygen attack the titanium carbide lattice, converting the conductive nanosheets into inert titanium dioxide and destroying the ordered layered structure that gives MXene its useful properties. A membrane that loses its MXene filler within weeks of operation would deliver none of the promised performance gains. The second obstacle is compatibility. Bare MXene nanosheets tend to aggregate and interact weakly with the surrounding polymer matrix, so instead of forming a continuous, well-bonded network they cluster into defects and voids that can actually worsen a membrane’s selectivity and mechanical integrity. These twin limitations, the authors note, have restricted MXene’s application in polymeric membranes for wastewater treatment.

The Khalifa University team’s solution was to functionalize the MXene with gallic acid before embedding it in the polymer. Gallic acid, a small molecule built around a benzene ring bearing three hydroxyl groups and one carboxylic acid group, belongs to the broad family of plant polyphenols. Its multiple oxygen-containing functional groups can interact strongly with the hydroxyl and oxygen termini already present on the MXene surface, effectively capping the nanosheets with an organic layer. That layer serves several purposes at once. It shields the underlying titanium carbide lattice from oxidative attack, dramatically improving the material’s oxidation stability in water. It improves the dispersion of the functionalized MXene, known as gMX, preventing the nanosheets from clumping together. And it creates a chemically compatible bridge between the inorganic nanosheet and the sulfonated polymer, improving the interfacial affinity between gMX and SPES so that the two phases bond as a coherent hybrid rather than separating into weakly connected domains.

Those interfacial interactions, the researchers found, ripple through every aspect of the resulting membrane. The way gMX disperses within the SPES matrix influences the membrane’s morphology, its pore-size distribution, its average pore size, its hydrophilicity and even its surface charge characteristics. In other words, by tuning the chemistry at the nanoscale interface between filler and polymer, the team gained control over the membrane’s structure and behavior at the macroscale. The polymer itself, sulfonated poly(ether sulfone), is a robust engineering plastic whose sulfonic acid groups confer hydrophilicity and negative surface charge, making it a sensible host for a charged, water-loving nanofiller. When the two components are well matched, the nanosheets act as reinforcing plates and water channels rather than as flaws.

The performance numbers reported for the optimized membrane are striking. At an optimal gMX loading of 2 weight percent, the membrane designated gMX2 achieved a pure-water flux of 16.4 liters per square meter per hour per bar, a 4.3-fold enhancement over the pristine SPES membrane. That means that, under the same driving pressure and through the same effective area, the hybrid membrane passes more than four times as much water as the unmodified polymer. In membrane engineering, flux is the currency of productivity: higher flux at a given pressure translates directly into smaller plants, lower pumping energy and cheaper treated water. Achieving a fourfold improvement by adding just two percent of a functionalized nanofiller illustrates how powerfully interfacial chemistry can amplify transport, since well-dispersed MXene sheets create continuous, hydrophilic pathways that draw water through the membrane far faster than the polymer alone allows.

Flux alone is meaningless, however, if the membrane cannot hold back contaminants. In separate single-solute tests, the optimized gMX2 membrane achieved greater than 95 percent rejection of selected dyes and pharmaceuticals under synthetic feed conditions. This is the defining characteristic of a tight ultrafiltration membrane: unlike conventional ultrafiltration, which passes most dissolved molecules and removes only suspended solids and large macromolecules, tight UF sits at the boundary between ultrafiltration and nanofiltration, with pores small enough and surface chemistry tuned enough to intercept small organic molecules such as dyes and active pharmaceutical ingredients. The combination of narrowed, well-distributed pores and a negatively charged, hydrophilic surface allows the membrane to reject these solutes through a combination of size exclusion and electrostatic repulsion while still maintaining the high flux that distinguishes ultrafiltration from denser, more energy-hungry nanofiltration and reverse osmosis membranes.

The most demanding test came when the researchers filtered real hospital wastewater spiked with pharmaceuticals, using a crossflow configuration in which the feed water sweeps continuously across the membrane surface for 24 hours. Crossflow operation is the industrially relevant mode, and fouling, the gradual buildup of rejected contaminants and organic matter on the membrane surface, is the perennial enemy that degrades performance over time. During the 24-hour run, the permeate flux of gMX2 settled at 11 liters per square meter per hour per bar, a decline from its clean-water value but a level the authors describe as reflecting improved flux stability and antifouling performance compared with a membrane containing unfunctionalized MXene, designated MX2. The hydrophilic, gallic-acid-modified surface resists the adhesion of foulants, so contaminants are more easily swept away by the crossflow rather than cementing themselves onto the membrane.

Removal of the pharmaceuticals themselves was more nuanced. In the hospital wastewater filtration, gMX2 achieved removal efficiencies of 77 percent for amitriptyline, an antidepressant abbreviated AMT, and 54 percent for ciprofloxacin, a widely used antibiotic abbreviated CIP, compared with the MX2 membrane. The difference between the two compounds is instructive: pharmaceuticals differ in molecular size, charge and affinity for the membrane surface, so no single membrane rejects all of them equally. Ciprofloxacin, in particular, can carry a positive or neutral charge depending on pH, which weakens electrostatic repulsion from the negatively charged membrane and allows more of it to pass. The authors position these results not as a complete solution but as support for gMX-SPES membranes as a pretreatment option, a first barrier that substantially reduces pharmaceutical loads in hospital wastewater before the stream reaches downstream treatment stages that can finish the job.

The broader significance of the work lies in its demonstration that a cheap, plant-derived molecule can rescue an otherwise fragile nanomaterial. Gallic acid is abundant, inexpensive and benign, and functionalizing MXene with it requires no exotic chemistry, which matters enormously if the membranes are ever to be manufactured at scale for real treatment plants. Hospital effluents are among the most concentrated point sources of pharmaceuticals in the urban water cycle, releasing antibiotics, antidepressants and other active compounds that drive antimicrobial resistance and disrupt aquatic ecosystems even at trace concentrations. A membrane that combines high flux, tight rejection, fouling resistance and stable operation in genuinely dirty water addresses the exact combination of properties that treatment engineers need. By solving the oxidation and compatibility problems that have held MXene back, the Abu Dhabi team has moved this promising two-dimensional material a meaningful step closer to working in the real world, one gallic-acid-wrapped nanosheet at a time.

Subject of Research: Gallic acid-functionalized Ti₃C₂Tₓ MXene/SPES hybrid tight ultrafiltration membranes for pharmaceutical removal from hospital wastewater

Article Title: Gallic acid functionalized Ti₃C₂Tₓ MXene/SPES hybrid tight ultrafiltration membranes with improved interfacial stability for wastewater treatment

Article References: Alansari, Z., Nassar, L., Kumar, M., Aboukhater, A., & Hasan, S. W. (2026). Gallic acid functionalized Ti₃C₂Tₓ MXene/SPES hybrid tight ultrafiltration membranes with improved interfacial stability for wastewater treatment. Advanced Composites and Hybrid Materials. https://doi.org/10.1007/s42114-026-02097-8

Image Credits: AI Generated

DOI: 10.1007/s42114-026-02097-8

Keywords: MXene, gallic acid, sulfonated poly(ether sulfone), tight ultrafiltration, hybrid membranes, wastewater treatment, pharmaceutical removal, antifouling, oxidation stability, membrane flux, hospital wastewater, Khalifa University

The team, led by Farah H. Omer of the University of Mosul and including investigators from the University of Babylon, the University of Anbar, and Ahvaz Jundishapur University of Medical Sciences in Iran, set out to answer a deceptively simple question: what is actually swimming in the water leaving hospitals in a mid-sized Iraqi city? To find out, they passed wastewater samples through cellulose ester membrane filters, a technique that traps bacteria on the filter surface while the liquid passes through. The trapped organisms were then cultured on cetrimide agar, a selective medium that favors Pseudomonas species and produces characteristic green pigmented colonies of P. aeruginosa. Suspected colonies were identified with a VITEK2 automated system, a workhorse of clinical microbiology laboratories, and every isolate was confirmed by polymerase chain reaction targeting the ecfX gene, a species-specific genetic marker that leaves little room for misidentification.

With the isolates confirmed, the researchers turned to antibiotic susceptibility testing using the disc diffusion method, following standards set by the Clinical and Laboratory Standards Institute. The results were sobering. Resistance to aztreonam, a monobactam antibiotic often used against gram-negative infections, reached 65.5 percent of isolates, while 58.8 percent resisted ceftazidime, a third-generation cephalosporin that is a mainstay of treatment for Pseudomonas infections. Ceftazidime resistance in this species is known to be multigenic and complex, involving combinations of reduced permeability, efflux pumps, and hydrolytic enzymes, which makes its high prevalence in wastewater isolates particularly concerning. Against this grim backdrop, one drug stood out: colistin, an older polymyxin antibiotic that has been revived as a last-resort agent, inhibited 89.9 percent of the isolates, making it by far the most effective compound tested.

The most alarming statistic, however, was the burden of multidrug resistance. Using standard definitions, the team classified 82.4 percent of the isolates, 98 of the 119 recovered, as multidrug-resistant, meaning they were nonsusceptible to at least one agent in three or more antimicrobial categories. That proportion rivals or exceeds what is often reported from clinical settings, where selective pressure from therapeutic antibiotic use is intense. Its presence in wastewater implies that the hospital drain is functioning as a selective reactor: bacteria exposed to a cocktail of residual antibiotics, disinfectants, and heavy metals are winnowed down to the hardiest strains, which then multiply and disperse. Environmental microbiologists have documented similar patterns in hospital effluents in the Czech Republic, South Africa, and elsewhere, but the Iraqi data underscore how widespread the phenomenon has become and how little containment typically occurs between the hospital sink and the municipal sewer.

Resistance alone does not make a bacterium dangerous; it must also carry the tools to cause disease. The researchers therefore screened every isolate by PCR for fourteen virulence genes spanning the major weapon systems of P. aeruginosa. The results read like a catalogue of the pathogen’s most feared capabilities. The toxA gene, which encodes exotoxin A, a potent inhibitor of protein synthesis that damages host cells, was present in 100 percent of the isolates. The lasB gene, which encodes elastase B, an enzyme that degrades elastin and other tissue proteins and helps the bacterium invade and spread, was found in 65.5 percent. The exoT gene, part of the type III secretion system that injects toxic effectors directly into host cells, appeared at the same frequency of 65.5 percent. Every one of these genes contributes to the tissue destruction and immune evasion that make P. aeruginosa infections so difficult to treat in burn wounds, lungs, and catheterized patients.

The wider virulence screen painted a picture of genetically well-armed populations. Genes encoding phospholipases C (plcH and plcN), which disrupt host cell membranes; exoenzymes S, T, U, and Y, the type III secreted effectors with distinct cytotoxic and immunomodulatory roles; alkaline protease (apr); the quorum-sensing and phenazine biosynthesis genes phzI and phzII, which govern pigment production and intercellular signaling; and the alginate biosynthesis genes algD and algU, which underpin the mucoid, antibiotic-impermeable biofilm phenotype, were all detected across the collection. The simultaneous presence of exoS and exoU alleles, which are usually considered largely mutually exclusive in clinical strains, has been noted before in environmental isolates and hints that wastewater populations may recombine and shuffle virulence determinants in ways that clinical populations do not.

Perhaps the most intriguing analytical step was the search for statistical relationships between virulence genes and antibiotic susceptibility. The team reported significant positive correlations between several gene pairs and specific drugs: algU with ciprofloxacin; phzII with piperacillin; phzI with imipenem, ceftazidime, and amikacin; plcN with imipenem; plcH with amikacin, piperacillin, and piperacillin-tazobactam; exoY with piperacillin; exoT with ceftazidime; and exoS with colistin. Correlation does not establish causation, and the authors did not claim direct genetic linkage between these loci and resistance mechanisms. But such associations are consistent with a scenario in which virulence and resistance traits are being co-selected in the same bacterial lineages, whether through shared mobile genetic elements, biofilm lifestyles that favor both traits, or the linkage of virulence determinants with efflux systems that pump out antibiotics. If hospital effluent consistently selects for strains that are both drug-tolerant and toxin-armed, the public health stakes rise considerably.

The study was approved by the Ethics Committee of the University of Babylon in November 2025 and involved no human or animal samples, sidestepping many of the logistical hurdles of clinical surveillance while capturing something clinical surveillance often misses: the environmental fate of pathogens after they leave the ward. Previous work in Iraq has documented cephalosporin resistance in clinical P. aeruginosa from Basra and the presence of resistance genes in water samples from Baghdad, and studies from Iran, China, Mexico, and Bangladesh have traced resistant and virulent strains in drinking water, groundwater, soil, and food. The Babylon data fit into this global mosaic and suggest that in regions where wastewater treatment is limited or absent, hospital effluents may serve as a continuous, largely unmonitored source of high-risk bacteria entering rivers, irrigation systems, and communities.

The authors’ conclusion is blunt: hospital effluents are critical sources of multidrug-resistant and virulent P. aeruginosa, and there is an urgent demand to improve wastewater management. That demand carries technical implications. Effective interventions could include on-site pretreatment of hospital effluent before discharge, enhanced monitoring of resistance and virulence markers in sewer networks, and stewardship programs that reduce the quantity of antibiotics entering the drain in the first place. The near-universal presence of toxA and the high frequency of lasB and exoT in these environmental isolates suggest that virulence screening, not just resistance testing, should inform risk assessments of hospital wastewater. As antimicrobial resistance continues to erode the clinical arsenal, with colistin remaining one of the few reliably effective agents, the drains of the world’s hospitals have become more than plumbing. They are, according to this study, active evolutionary arenas where the next generation of dangerous pathogens may be assembling, one selective pressure at a time.

Subject of Research: Virulence genes and antibiotic resistance in Pseudomonas aeruginosa from Iraqi hospital wastewater

Article Title: Virulence arsenal and antibiotic resistance backgrounds in Pseudomonas aeruginosa isolates from hospital wastewater samples from Iraq

Article References: Omer, F. H., Al-Khafaji, N. S. K., Shakir, B., Almjalawi, A., Al-Alaq, F. T., Al-Dahmoshi, H. O. M., Al-Ouqaili, M. T. S., Ahmad, F., & Saki, M. (2026). Virulence arsenal and antibiotic resistance backgrounds in Pseudomonas aeruginosa isolates from hospital wastewater samples from Iraq. Molecular Biology Reports, 53(1), Article 1654. https://doi.org/10.1007/s11033-026-12865-w

Image Credits: AI Generated

DOI: 10.1007/s11033-026-12865-w

Keywords: Pseudomonas aeruginosa, hospital wastewater, antimicrobial resistance, multidrug resistance, virulence genes, toxA, lasB, Iraq, colistin, PCR, public health, wastewater management

The team’s central concern was the formation of disinfection by-products. Chlorination remains the most common disinfection method worldwide because it is cheap, simple, and provides a lasting protective residual, but chlorine reacts vigorously with the dissolved organic matter that hospital effluents contain in abundance. These reactions generate organic acids, aldehydes, and trihalomethanes, compounds with documented risks to aquatic ecosystems and human health. Peracetic acid, by contrast, is a broad-spectrum antimicrobial oxidant that decomposes into water and acetic acid, by-products considered harmless to aquatic life. Its global market is projected to grow faster than any other water treatment disinfectant, and the study set out to test whether that enthusiasm is scientifically justified when pharmaceuticals such as antibiotics are present in the water.

To answer the question under controlled and reproducible conditions, the researchers prepared a synthetic hospital wastewater based on a published formulation containing carbohydrates, proteins, salts, and organic matter at concentrations resembling real hospital discharges. The mixture included glucose, sodium carbonate, ammonium sulfate, potassium phosphate, and trace metals, and yielded an average chemical oxygen demand of roughly 1044 milligrams per liter and a pH of about 9.38, values consistent with published characterizations of actual hospital effluents from Brazil, China, India, Iran, Turkey, Benin, and Vietnam. The team then inoculated the synthetic effluent with Escherichia coli at approximately 10^5 colony-forming units per milliliter, a level reported in real hospital wastewater, using the standard ATCC 25922 reference strain as an indicator organism.

The experimental design was deliberately rigorous. A full factorial experiment crossed two disinfectants, the presence or absence of the antibiotic amoxicillin, two disinfectant concentrations of 5 and 15 milligrams per liter, and two contact times of 5 and 15 minutes, producing sixteen treatments that were each run in triplicate for a total of 48 samples. Amoxicillin was selected because of its widespread clinical use and frequent detection in hospital effluents, and was added at 23.58 milligrams per liter to match concentrations measured in real wastewater by other researchers. Statistical analysis using one-way ANOVA followed by Tukey’s post hoc tests identified significant differences among treatments for chemical oxygen demand, pH, residual disinfectant concentrations, and bacterial removal efficiency.

The microbiological results were strikingly clear: both disinfectants substantially reduced E. coli across all conditions, and the highest doses delivered reductions exceeding four logarithmic units, equivalent to inactivating more than 99.99 percent of the bacteria. The single best performance came from sodium hypochlorite at 15 milligrams per liter over 15 minutes, which achieved a 5.28 log reduction with a calculated C·t value of 48.30 milligram-minutes per liter. Peracetic acid at the same dose achieved reductions of 5.15 and 4.73 logs. Even the weakest treatments, peracetic acid at 5 milligrams per liter, delivered reductions approaching three logs. These findings align with earlier work showing that peracetic acid can match or exceed chlorine in inactivating E. coli, coliphages, and Clostridium perfringens in water with high organic content, and even methicillin-resistant Staphylococcus aureus in hospital surface disinfection studies.

The chemistry told a more nuanced story. Every treatment produced a measurable rise in chemical oxygen demand relative to the raw effluent, because both oxidants convert recalcitrant organic compounds into more biodegradable forms that still register in the COD assay. Notably, samples containing amoxicillin consistently showed higher COD values than their drug-free counterparts, and the largest increase, reaching 1066.5 milligrams per liter, occurred when amoxicillin-laced effluent was treated with 15 milligrams per liter sodium hypochlorite for 15 minutes. This suggests that even a single antibiotic can measurably alter the behavior and by-product profile of disinfection, a factor that most treatment studies do not account for. All treatments also lowered the pH of the alkaline synthetic effluent, with the largest drops observed in the highest-dose chlorination runs, a pattern consistent with the known tendency of trihalomethane formation to increase at elevated pH.

Residual chemistry raised additional red flags for chlorine. Treatments using 15 milligrams per liter of sodium hypochlorite left total and free residual chlorine concentrations exceeding the 2 milligrams per liter discharge limit enforced by the local sanitation utility, and above the free chlorine range of 0.09 to 0.55 milligrams per liter measured in real hospital effluents by earlier investigators. Residual chlorine is toxic to aquatic organisms and can select for chlorine-resistant bacteria and propagate antibiotic resistance genes in downstream treatment plants. The researchers specifically tested for chloroform, the dominant trihalomethane typically produced during chlorination, in two high-dose samples, but concentrations fell below the analytical quantification limit of 0.005 milligrams per liter. The authors caution, however, that their synthetic matrix lacks the recalcitrant compounds found in real hospital effluent, where chlorination can generate haloacetic acids, haloacetonitriles, haloketones, trichloronitromethane, and chloral hydrate.

Peracetic acid residuals behaved predictably, with higher doses leaving higher residuals, and organic matter consuming much of the disinfectant within the first five minutes of contact, echoing prior observations that organic compounds demand peracetic acid rapidly while inorganic constituents such as iron consume it more slowly over about an hour. From an economic standpoint, the study notes that although peracetic acid has historically been more expensive than chlorine, its self-decomposing nature eliminates costly dechlorination steps, and its lower doses and shorter contact times can generate operational savings. The global peracetic acid market is projected to reach 1.3 billion dollars by 2026, with the wastewater segment growing at roughly eight percent annually, and combined peracetic acid followed by chlorine dosing has shown promise at full scale for facilities seeking better disinfection compliance.

The authors conclude that peracetic acid is a credible alternative to chlorination for hospital wastewater pre-treatment, offering comparable E. coli inactivation while producing by-products that do not harm the environment. They emphasize, however, that their work was conducted on synthetic effluent under controlled laboratory conditions, and that further studies using real hospital wastewater are needed to confirm the findings and fully characterize by-product formation. They also call for research into the toxic potential of hospital effluents, particularly in Brazil, where no specific legislation establishes discharge standards for hospital effluents entering public sanitary sewer systems. As concerns about antibiotic resistance and pharmaceutical pollution intensify worldwide, the humble choice of a disinfectant chemical may prove to be one of the most consequential decisions a hospital can make about its environmental footprint.

Subject of Research: Comparative evaluation of sodium hypochlorite and peracetic acid for disinfecting synthetic hospital wastewater and controlling disinfection by-products

Article Title: Evaluation of sodium hypochlorite and peracetic acid for disinfection of synthetic hospital wastewater

Article References: Koga, A., dos Santos, D. F., Martins, D. C. C., de Oliveira, L. T., de Abreu Filho, B. A., Benatti, C. T., & de Barros, M. A. S. D. (2026). Evaluation of sodium hypochlorite and peracetic acid for disinfection of synthetic hospital wastewater. Heliyon, 12(15), Article e45429. https://doi.org/10.1016/j.heliyon.2026.e45429

Image Credits: AI Generated

DOI: 10.1016/j.heliyon.2026.e45429

Keywords: hospital wastewater, disinfection, peracetic acid, sodium hypochlorite, E. coli, disinfection by-products, trihalomethanes, amoxicillin, chemical oxygen demand, antibiotic resistance, wastewater treatment, Heliyon