Search Results (290)

Disinfection is essential to ensure safe drinking water and hygienic conditions in environmental, industrial, and clinical settings. However, conventional methods for monitoring free residual chlorine are often laboratory-based and not suited for decentralized analysis. Here, we report a novel paper-based colorimetric biosensing platform that translates the ISO 7393-2 standard, a method based on the reaction of chlorine with N,N-diethyl-p-phenylenediamine (DPD), into a portable and user-friendly format. The proposed device integrates the DPD chemistry within a paper architecture, enabling reagent-free operation at the point of need. The sensor provides a rapid visual readout that is detectable by the naked eye, while quantitative analysis is achieved within 3 min through smartphone-based image acquisition. This work constitutes the first implementation of the ISO standard in a portable paper-based format suitable for both environmental and clinical matrices. The sensor provided a detection limit of 12 μM for sodium hypochlorite and was successfully validated in real samples, including bottled water and exhaled breath condensate, with satisfactory recoveries. Furthermore, the stability of the paper-based sensor was assessed under storage conditions of 4 °C and room temperature (23 °C), demonstrating excellent performance over 30 days in both cases, indicating that refrigeration is not required for maintaining sensor performance. Full article

This study proposes a methodology to identify deteriorated pipes in water distribution networks using prior system information and routine chlorine residual data. While bulk chlorine decay k_bulk can be measured in laboratories, wall decay k_wall depends on pipe material, diameter, and ageing, particularly in unlined metallic pipes. Empirical data were used to estimate k_wall, which was integrated into a Bayesian inference framework solved with Markov Chain Monte Carlo. Applied to an Italian network with synthetic chlorine data, this method demonstrated effectiveness across three test scenarios, exploiting the contrast between k_wall and k_bulk to detect deteriorated pipes within a computationally efficient environment. Full article

Volatile halogenated hydrocarbons (VHHs) are critical air toxic pollutants, with some ozone-depleting substances (ODSs) strictly regulated by the Montreal Protocol. However, current understanding of the pollution characteristics, sources, and health risks of atmospheric VHHs in Southwest China remains insufficient. This study performed field observations of atmospheric VHHs in summer in Mianyang, a medium-sized industrial city in the Sichuan Basin. Freon-12 (563 ± 20 ppt) and Freon-11 (264 ± 15 ppt) were the most abundant chlorofluorocarbons (CFCs); chloromethane (785 ± 261 ppt) and methylene chloride (563 ± 505 ppt) dominated among VSLSs. The mean concentration of regulated ODSs (1037 ± 33 pptv) was notably lower than unregulated very short-lived chlorinated substances (1887 ± 745 pptv), reflecting effective ODSs phase-out locally, yet enhancements relative to Northern Hemisphere background implied potential leakage from residual tanks. Methylene chloride and trichloroethylene concentrations exceeded global background levels by over 10 times, indicating strong anthropogenic industrial influences. Phased-out CFCs displayed negligible diurnal variation due to stringent emission controls, whereas unregulated VSLSs exhibited a distinct U-shaped diurnal cycle, with peaks driven by morning boundary layer dynamics and evening accumulation. Positive matrix factorization revealed that industrial sources, including electronic solvents (28.6%), industrial processes (27.8%), and solvent usage (23.7%), accounted for 80.1% of total VHHs. The total carcinogenic risk (2.3 × 10⁻⁵) surpassed the acceptable threshold (1 × 10⁻⁶), dominated by 1,2-dichloroethane, chloroform, carbon tetrachloride, and 1,2-dichloropropane. All individual compounds exhibited mean hazard quotients (HQs) below the non-carcinogenic risk threshold. The cumulative hazard index reached 1.5, suggesting combined non-carcinogenic risks to the local population. These results support VHHs health risk management and ODSs control in Southwest Chinese industrial cities. Full article

This paper studies a two-stage oxygen-alkaline treatment and subsequent bleaching of softwood sulfate pulp obtained from healthy and deadwood of spruce and larch. Delignification was carried out at elevated temperature and pressure in an alkaline medium with the addition of hydrogen peroxide, after which the pulp was subjected to classic ECF cycles with chlorine dioxide, hydrogen peroxide and, if necessary, elemental chlorine. The selected and washed mass was ground to a specified degree of grinding and formed into laboratory sheets of standard density on a sheet-forming apparatus. The results showed that oxygen-alkaline pretreatment significantly reduces the residual lignin content, and subsequent bleaching cycles make it possible to obtain high-brightness pulp with minimal losses of cellulose and viscosity. The structural, morphological and mechanical characteristics of the obtained samples were studied. After a full bleaching cycle, the fibers become slightly shorter and thinner, their surface is leveled, the proportion of small fractions decreases, and the homogeneity of the structure improves. The resulting cellulose samples demonstrate mechanical characteristics that meet industrial requirements for high-quality printing and thin-layer paper grades. Full article

The increasing generation of organic and liquid wastes calls for sustainable strategies to convert residues into valuable energy resources. This study investigates waste Oxytree biomass (Paulownia Clon In Vitro 112^®) as a sorbent for producing impregnated solid fuels from selected liquid wastes, including used cooking oil, spent mineral oil, and pyrolysis condensate, targeting industrial energy applications. Oxytree biomass was selected due to its high and predictable yield, uniform composition, and favorable physical properties compared to conventional lignocellulosic residues such as pine sawdust. Biomass and liquid wastes were characterized in terms of fuel properties and elemental composition. Several empirical combinations of sorbent and liquid fractions were tested to optimize homogeneity and fuel quality, resulting in a final composition of sorbent:used cooking oil:used machine oil:pyrolytic condensate equal to 3:1:1:3. The temporal stability of this selected fuel was verified over 24 h, 3 days, and 1 week. The resulting fuels exhibited an energy value of approximately 15 MJ/kg, low ash content (<1%), and minimal concentrations of chlorine and sulfur (<0.08%). Overall, the findings demonstrate that Oxytree waste biomass can serve as an effective sorbent for integrating problematic liquid wastes into solid fuels, providing a practical route for waste valorization and supporting circular economy principles, and establishing a foundation for further research on sustainable energy applications of biomass and industrial residues. Full article

In this study, lithium was recovered from LiFePO₄ (LFP) cathode active materials through a two-step thermal process combining hydrogen reduction and chlorination roasting. Hydrogen reduction was conducted while varying temperature and holding time to promote oxygen removal from LFP and induce phase separation into Li₃PO₄ and iron phosphides (FeP and Fe₂P). Based on stoichiometric assessment using the degree of LFP decomposition and the reduction in oxygen moles, the optimal hydrogen-reduction condition was determined to be 900 °C for 1 h. Subsequently, CaCl₂ was selected as an appropriate chlorination agent using thermodynamic considerations, and the hydrogen-reduced product was reacted with CaCl₂ to convert Li₃PO₄ into water-soluble LiCl. The mass of LiCl produced was quantified as a function of reaction temperature. Water leaching enabled the separation of LiCl from the insoluble residues, resulting in an overall lithium recovery of 71.7%. Full article

Vaporized free chlorine, primarily present as hypochlorous acid (HOCl), is increasingly used for indoor microbial control; however, virus-dependent susceptibility and its molecular determinants remain unclear. We evaluated virucidal effects under controlled indoor conditions (0–9 ppb) against echovirus 30 (E30), influenza A/H1N1, and human adenovirus type 3 (HAdV3). Infectious titers were quantified by TCID₅₀ assays. Computational fluid dynamics (CFD) simulations and gas-sensor measurements assessed spatial dispersion, and structural analyses examined oxidation-sensitive amino acid residues. Significant reductions in infectivity were observed for E30 (99.0%, p = 0.00727) and influenza A/H1N1 (99.9%, p = 0.000597), whereas no significant reduction was detected for HAdV3 (p = 0.142). Analyses including all data points without outlier exclusion confirmed the robustness of these findings. CFD indicated uniform dispersion, although spatial heterogeneity within the indoor environment cannot be excluded. These findings suggest that viral susceptibility to vaporized HOCl is associated with residue-level composition and structural context; however, this relationship should be interpreted as correlative rather than causal. Moreover, integration of molecular and structural analyses provides a plausible mechanistic framework, although direct biochemical validation remains necessary. Structural analyses showed lower proportions of oxidation-sensitive residues in adenoviral proteins compared with influenza A hemagglutinin (OR = 0.34–0.40, adjusted p < 0.001) and the E30 VP1 intermediate. Residues were clustered in surface-exposed functional domains in susceptible viruses. Full article

This study investigates how porous structure formation influences the properties and safety characteristics of composite rocket propellants. Particular attention was given to approaches that may support more sustainable propellant formulations and processing methods. The work compares the efficiency of different sample-structuring and foaming methods, including a chemical foaming strategy based on two ammonium salts. Additionally, it evaluates the feasibility of generating porosity in propellants containing glycidyl azide polymer through the retention of a low-boiling solvent, remaining from synthesis. This approach is expected to reduce the number of processing steps and simplify them, translating into lessened environmental impact. Propellants incorporating this polymer were found to exhibit consistent low-level porosity and improved performance compared to other ammonium nitrate-based propellants, constituting a potential sustainable alternative to perchlorate-based propellants. The investigation encompassed decomposition kinetics (including decomposition activation energy), combustion product analysis, and exploratory nitrogen porosimetry. From a sustainability perspective, the investigated approach addresses key limitations of perchlorate-based propellants by eliminating chlorine-containing oxidising agents and reducing the need for auxiliary chemicals. In particular, the physical foaming strategy enables pore formation using residual solvent, which is already present in the system, supporting waste minimisation and inherently safer processing. These aspects are discussed in the context of selected principles of Green Chemistry and fundamental properties–sustainability trade-offs. Overall, the results highlight how foaming method selection affects not only propellant behaviour but also opportunities for more resource-efficient and environmentally conscious manufacturing routes. Full article

The shipping sector is responsible for a considerable share of global CO₂ emissions and is under pressure to reduce emissions and adopt carbon-neutral fuels. Among the proposed alternatives, methanol produced from green hydrogen and biogenic CO₂ represents a promising option. However, the feasibility of its production is significantly influenced by the composition and variability of the bio-CO₂ feedstock, which can negatively impact the complete value chain. To address these challenges, sampling campaigns were carried out at actual bio-CO₂-emitting sites, namely biogas and biomass combustion facilities, to characterize the impurity profiles and determine the appropriate conditioning requirements. A novel membrane gas absorption system with a Diethanolamine solution was deployed directly in the field to capture, as well as purify to a certain extent, the CO₂ stream. The system demonstrated high efficiency in removing most impurities, achieving high CO₂ capture rates and impurity reduction close to 90%. However, residual chlorine species were detected in the CO₂ streams from biogas plants, suggesting the need for additional conditioning to meet the purity specifications required for methanol synthesis. Given that the feedstock composition and upstream process conditions could significantly affect the final output and present considerable variations, the implementation of additional cleaning measures is recommended before synthesis. Full article

This review work highlights the eco-friendly synthesis and application of biomass-derived silica gel (SG)-supported metallic nanoparticles (MNPs), primarily focusing on their potential for sustainable drinking water disinfection and utilizing abundant biomass waste, such as agricultural residues, to extract silica through processes like pyrolysis, chemical treatment, or hydrothermal methods, creating a versatile support with high surface area, porosity, and biocompatibility. MNPs, notably silver, copper, zinc, etc., are immobilized onto these silica frameworks via green synthesis techniques, including plant extract-mediated methods, chemical reduction, and sol–gel processes, resulting in nanocomposites with controlled size, distribution, and enhanced stability. These MNPs are known for their potent antimicrobial activity, capable of inactivating a broad spectrum of pathogens like Staphylococcus aureus and Escherichia coli. Silica gel supports mitigating issues such as nanoparticle aggregation and leaching, thus improving reusability and environmental safety. The synthesis parameters of nanoparticle size, concentration, surface chemistry, and contact time directly influence disinfection efficacy, while biomass-based supports offer advantages including cost-effectiveness, environmentally benign production, and minimal pollution. Incorporating biomass-derived silica gel-supported AgNPs into water treatment systems presents a promising, sustainable alternative to conventional chemical methods like chlorination and ultraviolet (UV) irradiation, which can generate hazardous byproducts. These nanocomposites demonstrate significant potential in resource-limited settings due to their high surface area, porosity, and reusability, although concerns such as nanoparticle leaching, toxicity, scalability, and environmental impact warrant further investigation. Overall, biomass-supported MNPs represent an innovative frontier in water purification technology, aligning with principles of green chemistry and sustainability. Emphasizing the importance of optimizing synthesis protocols and assessing long-term safety, this review underscores their capacity to advance eco-friendly water disinfection strategies that can improve public health and promote sustainable water management practices worldwide. Full article

Free chlorine removal from industrial wastewater using activated carbon filtration requires accurate modeling and optimal control to balance treatment efficiency and adsorbent consumption. In this study, a combined experimental–machine learning–optimization framework was developed to predict and optimize residual chlorine concentration in a pilot-scale activated carbon filtration unit. A total of 200 experimental runs were collected using a pilot activated carbon filtration system by varying flow rate, initial chlorine concentration, pressure, pH, temperature, and carbon dose. Two ensemble learning models, Random Forest (RF) and Gradient Boosting (GB), were trained and validated using five-fold cross-validation. Both models exhibited high predictive accuracy, with GB outperforming RF on the full dataset (R² = 0.9995, Root Mean Square Error (RMSE) = 0.0355 mg·L⁻¹, Mean Absolute Error (MAE) = 0.0276 mg·L⁻¹) and on the independent test set (R² = 0.9417). Feature importance and partial dependence analyses revealed that the initial chlorine concentration and activated carbon dose were the dominant controlling variables, while increasing flow rate led to higher residual chlorine levels. A multi-objective optimization strategy based on Pareto dominance was implemented using the trained GB model as a surrogate to simultaneously minimize residual chlorine and carbon consumption. The optimal compromise solution corresponded to an activated carbon dose of approximately 51.5 kg and a residual chlorine concentration of 0.156 mg·L⁻¹ at a flow rate of 43.1 m³·h⁻¹. The proposed framework demonstrates a reliable and cost-effective approach for predictive control and sustainable optimization of dechlorination processes in industrial wastewater treatment. Full article

Background: Surface chemistry and cleanliness are widely regarded as important factors influencing the host response to titanium dental implants. Despite advances in manufacturing and sterilization, trace residues may persist at the nanoscale even in commercially sterile devices. This study provides a preliminary evaluation of premium-grade titanium dental implants using time-of-flight secondary ion mass spectrometry (ToF-SIMS) to assess surface chemical uniformity and trace contaminant distribution. Method: Two commercially available titanium implants from Schütz Dental were analyzed under static and dynamic ToF-SIMS modes using Bi₃⁺ and Cs⁺ ion beams. Both positive and negative ion spectra were collected to identify elemental and molecular species. Chemical mapping and depth profiling were performed to evaluate contaminant distribution and surface depth composition. Results: In the two implants analyzed, the surfaces were dominated by TiO⁺ and TiO₂⁺ species, consistent with a native titanium oxide layer. In both analyzed implants, localized contaminants—including fluorine, chlorine, sulfur, CN groups, and organic residues—were detected within the outermost ~0.1 µm. These signals showed heterogeneous distribution along the thread-related regions within the analyzed ROIs, compatible with residues originating from machining, surface treatments, packaging, and/or sterilization steps. Conclusions: The present data support only the descriptive finding that trace contaminants were detected on the two analyzed implants. ToF-SIMS enabled nanoscale chemical mapping and depth profiling of these residues, supporting the feasibility of this approach for trace-level surface auditing and hypothesis generation. Any biological/clinical implications remain speculative and require dedicated in vitro/in vivo validation on larger sample sets. Full article

Nature-based solutions, including green infrastructure (GI), are considered sustainable tools for stormwater treatment. GI elements (rain gardens, green roofs, etc.) are increasingly applied as integrated approaches for climate change mitigation and environmental pollution reduction. This study focused on investigations of rain gardens for reducing stormwater polluted by residual chlorine after the disinfection of outdoor spaces. Laboratory (column test) and field tests were carried out to evaluate the infiltration capacities of an experimental rain garden model, as well as its efficiency for retaining residual chlorine. The experiments were conducted using simulated rain garden layers composed of waste materials that remained after different production processes. The average infiltration coefficient values obtained were 2.55 × 10⁻⁵ m/s, 2.45 × 10⁻⁵ m/s, 2.24 × 10⁻⁵ m/s, 3.4 × 10⁻⁵ m/s, 1.28 × 10⁻⁵ m/s, 1.84 × 10⁻⁵ m/s (laboratory test), and 1.39 × 10⁻⁵ m/s (field test). These values correspond to the characteristics of sand–gravel substrates. A chlorine retention efficiency of 82.5–87% was obtained. Granulometric analysis confirmed fraction size suitability for rain garden filtration. This research indicates the potential of rain gardens for reducing stormwater pollution, providing a basis for future research and practical implementation. Full article

To achieve an atomically clean surface of single-crystal aluminum nitride (AlN) substrates, this study systematically evaluated the effects of each step in ex situ wet chemical cleaning (solvent, piranha solution, HF, HCl) and in situ hydrogen annealing. X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) analyses revealed that while the combination of solvent and piranha solution exposed step morphology, its effectiveness in removing organic contaminants was limited. HF cleaning efficiently removed the oxide layer but introduced fluorine residues, whereas HCl cleaning left no chlorine residues but exhibited lower efficiency in oxide removal. In situ hydrogen annealing significantly reduced carbon and oxygen contamination, albeit accompanied by a transformation of the surface morphology from step to island mode. By modulating the low V/III ratio during low-temperature metal–organic chemical vapor deposition (MOCVD) growth, a controlled transition from 3D island growth to 2D step-flow growth was achieved. This research provides a basis for optimizing AlN substrate surface treatment, offering important insights for advancing nitride-based optoelectronic and power devices. Full article

To meet the demand for ultra-high-purity arsenic (≥7N) from crude arsenic (As ≥ 99.3%, Sb ≤ 0.6%), an integrated process combining chlorination, distillation and hydrogen reduction was developed. After preliminary purification of crude arsenic by vacuum distillation, chlorine was applied to convert arsenic and its impurities into chlorides. Low-boiling chlorides such as SbCl₃, S₂Cl₂ and Se₂Cl₂ were separated by distillation, and ultra-pure AsCl₃ was finally reduced by hydrogen to obtain ultra-high-purity arsenic. Under optimal conditions—10 mL·min⁻¹ Cl₂ flow, 20 mm–30 mm arsenic particle size and 80 mm–90 mm packing height—the chlorine utilization reached 92.3%. Distillation at 433 K with 4 h total reflux and a 5:1 volumetric reflux ratio yielded AsCl₃ of 99.99999% purity, with S and Se below 0.02 ppm and 0.01 ppm, respectively. Hydrogen reduction at 1123 K, H₂/AsCl₃ molar ratio 1.8 and 623 K condensation temperature achieved an arsenic recovery of 99.13%, a chlorine residue of 20 ppb and a final arsenic purity of 99.9999%. This study provides a feasible route for large-scale production of high-purity arsenic. Full article