Effective radioactive strontium removal using lithium titanate decorated Ti3C2Tx MXene/polyacrylonitrile beads.

A lithium titanate-decorated Ti3C2Tx MXene (LTO-MX) composite was synthesized through etching and alkali processes, and subsequently immobilized using polyacrylonitrile (PAN) polymer via a phase inversion method. In the batch study, the strontium adsorption behavior followed the Redlich-Peterson isotherm and the pseudo-second-order kinetic models. The maximum adsorption capacity for strontium reached 24.05 mg/g. Furthermore, a continuous fixed-bed column study was performed using the LTO-MX PAN beads to remove strontium from aqueous solutions. The dynamic behavior of column adsorption was examined under various operating parameters such as initial strontium concentration, flow rate, and bed height. Dynamic modeling was employed to describe adsorption breakthrough properties based on these experimental data. Both the Thomas and Yoon-Nelson models accurately simulated the breakthrough curves. The proposed mechanisms for strontium adsorption included encapsulation, electrostatic attraction, cation exchange, and surface complexation. These results demonstrate the effectiveness of LTO-MX PAN beads as adsorbents for the continuous removal of strontium from radioactive wastewater.

Experimental analysis and prediction of radionuclide solubility using machine learning models: Effects of organic complexing agents.

Radioactive wastes contain organic complexing agents that can form complexes with radionuclides and enhance the solubility of these radionuclides, increasing the mobility of radionuclides over great distances from a radioactive waste repository. In this study, four radionuclides (cobalt, strontium, iodine, and uranium) and three organic complexing agents (ethylenediaminetetraacetic acid, nitrilotriacetic acid, and iso-saccharic acid) were selected, and the solubility of these radionuclides was assessed under realistic environmental conditions such as different pHs (7, 9, 11, and 13), temperatures (10 °C, 20 °C, and 40 °C), and organic complexing agent concentrations (10-5-10-2 M). A total of 720 datasets were generated from solubility batch experiments. Four supervised machine learning models such as the Gaussian process regression (GPR), ensemble-boosted trees, artificial neural networks, and support vector machine were developed for predicting the radionuclide solubility. Each ML model was optimized using Bayesian optimization algorithm. The GPR evolved as a robust model that provided accurate predictions within the underlying solubility patterns by capturing the intricate relationships of the independent parameters of the dataset. At an uncertainty level of 95%, both the experimental results and GPR simulated estimations were closely correlated, confirming the suitability of the GPR model for future explorations.

Optimization of electrochemical regeneration of intercalated MXene for the adsorptive removal of ciprofloxacin: Prospective mechanism.

2D-Ti3C2Tx MXene nanosheets intercalated with sodium ions (SI-Ti3C2Tx) were synthesized and utilized in simultaneous adsorption and electrochemical regeneration with ciprofloxacin (CPX). The primary focus of this study is to investigate the long-term stability of SI-Ti3C2Tx MXene and to propose the underlying regeneration mechanisms. The successful synthesis of Ti3AlC2, Ti3C2Tx MXene, and SI-Ti3C2Tx MXene was confirmed using X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy. Electrochemical regeneration parameters such as charge passed, regeneration time, current density, and electrolyte composition were optimized with values of 787.5 C g-1, 7.5 min, 10 mA cm-2, and 2.5w/v% sodium chloride, respectively, enabling the complete regeneration of the SI-Ti3C2Tx MXene. In addition, the electrochemical regeneration significantly enhanced CPX removal from the SI-Ti3C2Tx MXene owing to partial amorphization, disorderliness, increased functional groups, delamination, and defect creation in the structure. Thus, the synthesized nano-adsorbent has proven helpful in practical water treatment with optimized electrochemical regeneration processes.

Sodium-alginate-laden MXene and MOF systems and their composite hydrogel beads for batch and fixed-bed adsorption of naproxen with electrochemical regeneration.

Sodium alginate (SA)-laden two-dimensional (2D) Ti3C2Tx MXene (MX) and MIL-101(Fe) (a type of metal-organic framework (MOF)) composites were prepared and used for the removal of naproxen (NPX), following the adsorption and electrochemical regeneration processes. The fixed-bed adsorption column studies were also conducted to study the process of removal of NPX by hydrogels. The number of interactions via which the MX-embedded SA (MX@SA) could adsorb NPX was higher than the number of pathways associated with NPX adsorption on the MIL-101(Fe)-embedded SA (MIL-101(Fe)@SA), and the MX and MIL-101(Fe) composite embedded SA (MX/MIL-101(Fe)@SA). The optimum parameters for the electrochemical regeneration process were determined: charge passed and current density values were 169.3 C g-1 and 10 mA cm-2, respectively, for MX@SA, and the charge passed and current density values were 16.7 C g-1 and 5 mA cm-2, respectively, for both MIL-101(Fe)@SA and MX/MIL-101(Fe)@SA. These parameters enabled excellent regeneration, consistent over multiple adsorption and electrochemical regeneration cycles. The mechanism for the regeneration of the materials was proposed that the regeneration of MX@SA and MIL-101(Fe)@SA involved the indirect electrooxidation process in the presence of OH radicals, and the regeneration of MX/MIL-101(Fe)@SA involved the indirect oxidation process in the presence of active chlorine species.

Enhanced biodegradation of perfluorooctanoic acid in a dual biocatalyzed microbial electrosynthesis system.

The toxic perfluorooctanoic acid (PFOA) is widely spread in terrestrial and aquatic habitats owing to its resistance to conventional degradation processes. Advanced techniques to degrade PFOA requires drastic conditions with high energy cost. In this study, we investigated PFOA biodegradation in a simple dual biocatalyzed microbial electrosynthesis system (MES). Different PFOA loadings (1, 5, and 10 ppm) were tested and a biodegradation of 91% was observed within 120 h. Propionate production improved and short-carbon-chain PFOA intermediates were detected, which confirmed PFOA biodegradation. However, the current density decreased, indicating an inhibitory effect of PFOA. High-throughput biofilm analysis revealed that PFOA regulated the microbial flora. Microbial community analysis showed enrichment of the more resilient and PFOA adaptive microbes, including Methanosarcina and Petrimonas. Our study promotes the potential use of dual biocatalyzed MES system as an environment-friendly and inexpensive method to remediate PFOA and provides a new direction for bioremediation research.

Enhanced bio-electrochemical performance of microbially catalysed anode and cathode in a microbial electrosynthesis system.

Most bio-electrochemical systems (BESs) use biotic/abiotic electrode combinations, with platinum-based abiotic electrodes being the most common. However, the non-renewability, cost, and poisonous nature of such electrode systems based on noble metals are major bottlenecks in BES commercialisation. Microbial electrosynthesis (MES), which is a sustainable energy platform that simultaneously treats wastewater and produces chemical commodities, also faces the same problem. In this study, a dual bio-catalysed MES system with a biotic anode and cathode (MES-D) was tested and compared with a biotic cathode/abiotic anode system (MES-S). Different bio-electrochemical tests revealed improved BES performance in MES-D, with a 3.9-fold improvement in current density compared to that of MES-S. Volatile fatty acid (VFA) generation also increased 3.2-, 4.1-, and 1.8-fold in MES-D compared with that in MES-S for acetate, propionate, and butyrate, respectively. The improved performance of MES-D could be attributed to the microbial metabolism at the bioanode, which generated additional electrons, as well as accumulative VFA production by both the bioanode and biocathode chambers. Microbial community analysis revealed the enrichment of electroactive bacteria such as Proteobacteria (60%), Bacteroidetes (67%), and Firmicutes + Proteobacteria + Bacteroidetes (75%) on the MES-S cathode and MES-D cathode and anode, respectively. These results signify the potential of combined bioanode/biocathode BESs such as MES for application in improving energy and chemical commodity production.

The value of the sacroiliac joint area as a new morphological parameter of ankylosing spondylitis.

A narrowed sacroiliac joint (SIJ) space has been considered to be a major morphologic parameter of ankylosing spondylitis (AS). Previous studies revealed that the sacroiliac joint thickness (SIJT) correlated with AS in patients. However, irregular narrowing is different from thickness. Thus, we devised a method using the sacroiliac joint cross-sectional area (SIJA) as a new morphological parameter for use in evaluating AS. We hypothesized that the SIJA is a key morphologic parameter in diagnosing AS. SIJ samples were collected from 107 patients with AS, and from 85 control subjects who underwent SIJ-view X-rays that revealed no evidence of AS. We measured the SIJT and SIJA at the SIJ margin on X-rays using our picture archiving and communications system. The SIJT was measured at the narrowest point between the sacrum and the ilium. The SIJA was measured as the entire cross-sectional joint space area of the SIJ in the X-ray images. The average SIJT was 3.09 ±â€…0.61 mm in the control group, and 1.59 ±â€…0.52 mm in the AS group. The average SIJA was 166.74 ±â€…39.98 mm2 in the control group, and 68.65 ±â€…24.11 mm2 in the AS group. AS patients had significantly lower SIJT (P < .001) and SIJA (P < .001) than the control subjects. Receiver operating characteristics curve analysis showed that the best cutoff point for the SIJT was 2.33 mm, with 92.5% sensitivity, 94.1% specificity, and an area under the curve of 0.97 (95% confidence interval: 0.95-0.99). The optimal cutoff point for the SIJA was 106.19 mm2, with 93.5% sensitivity, 95.3% specificity, and an area under the curve of 0.98 (95% confidence interval: 0.97-1.00). Although the SIJT and SIJA were both significantly associated with AS, the SIJA parameter was a more sensitive measurement. We concluded that the SIJA is an easy-to-use, fast, cheap, and useful new morphological parameter for predicting AS.

Electrocatalytic oxidation of antidiabetic drug metformin adsorbed on intercalated MXene.

Two-dimensional (2D) Ti3C2Tx transition metal carbide (MXene) nanosheets intercalated with sodium ions (SI-Ti3C2Tx MXene) were used in the adsorption and electrochemical regeneration process for removal of the antidiabetic drug metformin (MF) as a model emerging pollutant. After MF adsorption, SI-Ti3C2Tx MXene oxidized the MF on its surface through its electrocatalytic activity at very low current density and cell potential. For complete oxidation the optimum parameters were 0.525 C g-1, 0.005 mA cm-2, and pH 6 in absence of NaCl or 26.25 C g-1 and 0.5 mA cm-2 in the presence of 2.5 w/v% NaCl. The overall regeneration of SI-Ti3C2Tx is governed by a combined mechanism, i.e., desorption followed by degradation. The degradation mechanism, such as direct electron transfer or indirect oxidation, depends on the applied operating conditions. Thus, the investigation suggests that these 2D sheets are good nanoadsorbents as well as good electrocatalysts and proves their usefulness in practical water-treatment applications.

Buckwheat hull-derived biochar immobilized in alginate beads for the adsorptive removal of cobalt from aqueous solutions.

Buckwheat hull-derived biochar (BHBC) beads were synthesized by immobilizing biochar powder with alginate. Due to their cation-exchange ability, abundant functional groups, microporous structure, and large surface area, BHBC beads were successfully applied for the removal of cobalt from aqueous solution. The adsorption behavior followed pseudo-second-order kinetics and the Langmuir isotherm model showed a better fit to adsorption data than the Freundlich or Temkin isotherm models. The maximum adsorption capacity of BHBC beads was 24.0 mg/g at pH 5, 35 °C, and an initial cobalt concentration of 1.0 g/L, which was higher than those of previously reported natural resource-based adsorbents. In a fixed-bed column study, the effects of operating parameters such as flow rate, bed height, and bed diameter were investigated. Both the Thomas and Yoon-Nelson models were applied to the experimental data to predict the breakthrough curves using nonlinear regression. Overall, BHBC beads can be used as an efficient adsorbent for removal of radioactive cobalt from aqueous solution.

MXsorption of mercury: Exceptional reductive behavior of titanium carbide/carbonitride MXenes.

Two-dimensional (2D) transition metal carbides and nitrides (MXenes) have drawn considerable attention for application in the field of environmental remediation. In this study, we report the simultaneous reductive-adsorption behavior of Ti3CNTx for toxic metal ion Hg2+ ion in the aqueous phase. 2D Ti3CNTx and Ti3C2Tx MXene nanosheets were synthesized by exfoliation of Ti3AlCN and Ti3AlC2 MAX phases, respectively. Various characteristics analysis confirmed the successful fabrication of MAX phases and their exfoliation into MXenes. The fabricated MXene nanosheets were used to investigate their Hg2+ removal, Hg2+ intercalation, and surface interaction mechanism efficiencies. Both MXenes were found to adsorb and reduce a large amount of Hg2+. Analytical techniques such as X-ray powder diffraction, field emission transmission electron microscopy, zeta-potential analyses, and X-ray photoelectron spectroscopy were used to investigate the material characteristics and structural changes after uptake of Hg2+. The quantitative investigation confirmed the interaction of bimetal and hydroxyl groups with Hg2+ using electrostatic interactions and adsorption-coupled reduction. In addition, both MXenes exhibited extraordinary Hg ion removal capabilities in terms of fast kinetics with an excellent distribution coefficient (KdHg) up to 1.36 × 10+9. Based on batch adsorption results, Ti3C2Tx and Ti3CNTx exhibited removal capacities of 5473.13 and 4606.04 mg/g, respectively, for Hg2+, which are higher than those of previous Hg adsorbents.

Exfoliation of Titanium Aluminum Carbide (211 MAX Phase) to Form Nanofibers and Two-Dimensional Nanosheets and Their Application in Aqueous-Phase Cadmium Sequestration.

A green approach was adopted to exfoliate a Ti2AlC MAX phase. The exfoliated nanostructures (Alk-Ti2Cfibr and Alk-Ti2Csheet) with exceptional mechanical, thermal, and water stabilites, as well as abundant oxygenated active binding sites, were synthesized via a controlled hydrothermal treatment in an alkaline environment. The successful synthesis of nanofibers and sheetlike nanostructures was inferred with scanning electron microscopy and X-ray diffraction analyses. Field emission scanning electron microscopy, field-emission transmission electron microscopy, Raman spectroscopy, Brunauer-Emmett-Teller surface area, ζ-potential analyses, and X-ray photoelectron spectroscopy were utilized to investigate the material's characteristics and its structural changes after metal ion adsorption. Heavy metal ion adsorption of the synthesized nanostructures was assessed in batch tests based on Cd2+ ion sequestration; the maximum adsorption capacity for Cd2+ was 325.89 mg/g, which is among the highest values reported for similar materials such as graphene oxide and its derivatives. The detailed quantitative investigation confirmed the interaction of hydroxyl groups with Cd2+ ions by electrostatic interactions, adsorption-coupled oxidation, and complex formation. Owing to their unique structure, high porosity, large specific surface area, and oxygenated functional groups, Alk-Ti2Csheet nanosheets were highly time-efficient for Cd2+ removal. Moreover, Alk-Ti2Cfibr and Alk-Ti2Csheet nanostructures were tested for simulated groundwater, showing that synthesized nanostructures were capable for removing Cd2+ ions at the ppb level. The results obtained from this study suggested that nanostructures synthesized using this route could provide a new approach to prepare and exfoliate additional MAX phases for the removal of heavy metal ions and other pollutants in the environment.

The secretory products of Trichomonas vaginalis decrease fertilizing capacity of mice sperm in vitro.

Trichomonas vaginalis infection is one of the most prevalent sexually transmitted infections in humans and is now recognized as an important cause of infertility in men. There is little information about the effect of extracellular polymeric substances (EPS) from T. vaginalis on sperm, but previous reports do not provide a conclusive description of the functional integrity of the sperm. To investigate the impact of EPS on the fertilizing capacity of sperm, we assessed sperm motility, acrosomal status, hypo-osmotic swelling, and in vitrofertilization rate after incubating the sperm with EPS in vitrousing mice. The incubation of sperm with EPS significantly decreased sperm motility, viability, and functional integrity in a concentration and time-dependent manner. These effects on sperm quality also resulted in a decreased fertilization rate in vitro. This is the first report that demonstrates the direct negative impact of the EPS of T. vaginalis on the fertilization rate of sperm in vitro. However, further study should be performed using human sperm to determine if EPS has similar negative impact on human sperm fertilizing capacity in vitro.

Delayed human neutrophil apoptosis by Trichomonas vaginalis lysate.

Neutrophils play an important role in the human immune system for protection against such microorganisms as a protozoan parasite, Trichomonas vaginalis; however, the precise role of neutrophils in the pathogenesis of trichomoniasis is still unknown. Moreover, it is thought that trichomonal lysates and excretory-secretory products (ESP), as well as live T. vaginalis, could possibly interact with neutrophils in local tissues, including areas of inflammation induced by T. vaginalis in humans. The aim of this study was to investigate the influence of T. vaginalis lysate on the fate of neutrophils. We found that T. vaginalis lysate inhibits apoptosis of human neutrophils as revealed by Giemsa stain. Less altered mitochondrial membrane potential (MMP) and surface CD16 receptor expression also supported the idea that neutrophil apoptosis is delayed after T. vaginalis lysate stimulation. In contrast, ESP stimulated-neutrophils were similar in apoptotic features of untreated neutrophils. Maintained caspase-3 and myeloid cell leukemia-1 (Mcl-1) in neutrophils co-cultured with trichomonad lysate suggest that an intrinsic mitochondrial pathway of apoptosis was involved in T. vaginalis lysate-induced delayed neutrophil apoptosis; this phenomenon may contribute to local inflammation in trichomoniasis.