Search Results (1,920)

The utilization of carbon dioxide (CO₂) offers an effective approach for alleviating the carbon-reduction pressures associated with fossil energy consumption. However, studies on the use of CO₂ as an auxiliary agent in water treatment to enhance the removal of emerging contaminants are limited. In this study, the photodegradation of ciprofloxacin (CIP) was investigated using ultraviolet (UV) irradiation combined with CO₂ dosing (UV/CO₂). The results demonstrated that the UV/CO₂ system effectively degraded CIP, with CO₂ concentration and solution pH exerting a critical influence. Inorganic anions and metal cations had negligible effects on CIP degradation efficiency, whereas natural organic matter (NOM) had a pronounced inhibitory effect. Mechanistic analysis revealed that superoxide radicals ($·{\mathrm{O}}_2^{-}$) and carbonate radicals (${\mathrm{CO}}_3^{•-}$) were the primary oxidizing species, whereas the excited triplet state of CIP (³CIP*) and singlet oxygen played crucial roles in initiating radical generation. LC–MS analysis and density functional theory calculations indicated that the main degradation routes involved defluorination, decarboxylation, and epoxidation of the piperazine ring. Toxicity assessment indicated that the transformation products generated by UV/CO₂ were less toxic than the parent compound. Furthermore, the UV/CO₂ process demonstrated high energy efficiency, with a low electrical energy per order (EEO) value of 0.4193 kWh·m⁻³·order⁻¹. These findings suggest that the UV/CO₂ system is a promising alternative for the treatment of photosensitive organic pollutants and provides a beneficial pathway for CO₂ utilization. Full article

The analysis of time-resolved S₁–S_n absorption spectra in the 0–500 ps range, together with quantum-chemical calculations, uncovered a photorecoordination reaction for the following complexes of CD6 (a bis(aza-18-crown-6)-containing dienone (ketocyanine dye) with a central cyclohexanone fragment): CD6·(Mⁿ⁺)₂ (M = Ba²⁺, Sr²⁺, Ca²⁺, K⁺). This process takes place over hundreds of fs and involves an “axial-to-equatorial” conformational change, with the solvation shell undergoing rearrangement as well. The characteristic photorecoordination times were found to correlate with the stability constants of the complexes. The lifetimes for the fluorescent states of CD6 and its complexes, namely CD6·(Mⁿ⁺)₂ (M = Ba²⁺, Sr²⁺, Ca²⁺, K⁺), are different; ergo, there is no photoejection of crowned cations into the solution. The calculated conformational profiles in the ground and excited states indicate the presence of an energy barrier in this process. A general photorelaxation pathway is suggested for CD6·(Mⁿ⁺)₂ metal complexes (M = Ba²⁺, Sr²⁺, Ca²⁺, K⁺). The coordination of cations via the carbonyl moiety in the dye molecule promotes photorecoordination of metal cations in the cavities of the azacrown ether fragment. Photorecoordination times were found to correlate with the degree of conjugation between the lone pairs in the N atoms of the aza-18-crown-6 ether and the π subsystem in the dye molecules (established for the CD4–CD6 metal–dye complex series, where CD4 and CD5 are related dyes with central cyclobutanone and cyclopentanone fragments, respectively). Full article

This work introduces 2-(azulen-1-yldiazenyl)-5-(thiophen-2-yl)-1,3,4-thiadiazole (L) as a functional monomer capable of forming stable, redox-active films with high affinity for lead in aqueous solutions. L was synthesized and characterized using physical chemical methods and electrochemistry. Polymer films of L were prepared through oxidative electro polymerization on glassy carbon electrodes in L solutions in 0.1 M TBAP in acetonitrile. They were characterized through electrochemistry. The surface of chemically modified electrodes (CMEs) prepared through controlled potential electrolysis (CPE) at variable concentrations, potentials, and electric charges was characterized through scanning electron spectroscopy, atomic force microscopy, and Raman spectroscopy, which confirmed the films’ formation. Electrochemical sensing of the films deposited on these CMEs was tested with respect to heavy metal (HM) ion analysis in aqueous solutions to obtain sensors for HMs. The obtained CMEs presented the best characteristics for the recognition of Pb among the investigated HMs (Cd, Pb, Cu, and Hg). Calibration curves were obtained for the analysis of Pb(II) in aqueous solutions, which allowed for the estimation of a good detection limit of this cation (<10⁻⁸ M) for non-optimized CMEs. The resulting CMEs show promise for deployment in portable environmental monitoring systems, with implications for public health protection and environmental safety. Full article

Soil contamination with heavy metals (HM) poses a risk to human health and can impact different soil functions. This study aimed to determine the influence of heavy metal pollution on the physical and physicochemical characteristics of the two profiles of alluvial–deluvial soil under grassland located at different distances from the Aurubis-Pirdop Copper smelter in Bulgaria. Data for soil particle-size distribution, soil bulk and particle densities, mineralogical composition, soil organic carbon contents, cation exchange properties, surface charge, soil water retention curves, pore size distribution—obtained by mercury intrusion porosimetry (MIP)—and thermal properties were obtained. The contents of Pb, Cu, As, Zn, and Cd were above the maximum permissible level in the humic horizon and decreased with depth and distance from the Copper smelter. Depending on HM speciation, the correlations are established with SOC and most physicochemical parameters. It can be concluded that the HMs impact the clay content, specific surface area, distribution of pores, and the water stability of soil aggregate fraction 1–3 mm to varying degrees. Full article

Although transition metal catalysts have been used extensively for the polymerization of hydrocarbon monomers, several cationic aluminum catalysts have been also known to promote polymerization of ethylene and 1,3-butadiene. Transition-metal catalyzed polymerization generally proceeds via coordination and insertion of the monomer on one metal center. In contrast, in ethylene polymerization using aluminum catalysts, a bimolecular chain growth mechanism, including the reaction between neutral aluminum species and the monomer activated by cationic aluminum species, is proposed. Although previously reported aluminum catalysts are based on a monoaluminum complex, a dialuminum complex is expected to catalyze the polymerization more efficiently, considering the proposed mechanism. In this work, we found that a combination of diphosphines and MAO promotes polymerization of ethylene and 1,3-butadiene. The 1,4-bis(diphenylphosphino)butane (DPPB)/methylaluminoxane (MAO) system showed a much higher activity toward ethylene polymerization than other monophosphine or diphosphine/MAO systems. NMR analysis of a mixture of diphosphine and MAO indicates the formation of cationic dialuminum species in the presence of DPPB, whereas the formation of cationic monoaluminum species occurs in the presence of other diphosphines. The 2,2′-bis(diphenylphosphino)-1,1′-biphenyl (BIPHEP)/MAO system promoted 1,3-butadiene polymerization to give polybutadiene having a cis-1,4 selectivity of up to 93.8%. Full article

This study systematically explores the mechanisms and application potential of biochar in remediating heavy metal-contaminated soils. Particular emphasis is placed on the role of raw materials and pyrolysis conditions in modulating key physicochemical properties of biochar, including its aromatic structure, porosity, cation exchange capacity, and ash content, which collectively enhance heavy metal immobilization. The direct remediation mechanisms are categorized into six pathways: physical adsorption, electrostatic interactions, precipitation, ion exchange, organic functional group complexation, and redox reactions, with particular emphasis on the reduction in toxic Cr⁶⁺ and the oxidation of mobile As³⁺. In addition to direct interactions, biochar indirectly facilitates remediation by enhancing soil carbon sequestration, improving soil physicochemical characteristics, stimulating microbial activity, and promoting plant growth, thereby generating synergistic effects. The study evaluates combined remediation strategies integrating biochar with phytoremediation and microbial remediation, highlighting their enhanced efficiency. Moreover, practical challenges related to the long-term stability, ecological risks, and economic feasibility in field applications are critically analyzed. By synthesizing recent theoretical advancements and practical findings, this research provides a scientific foundation for optimizing biochar-based soil remediation technologies. Full article

Rechargeable aqueous Zn-MnO₂ batteries are positioned as a highly promising candidate for next-generation energy storage, owing to their compelling combination of economic viability, inherent safety, exceptional capacity (with a theoretical value of ≈308 mAh·g⁻¹), and eco-sustainability. However, this system still faces multiple critical challenges that hinder its practical application, primarily including the ambiguous energy storage reaction mechanism (e.g., unresolved debates on core issues such as ion transport pathways and phase transition kinetics), dendrite growth and side reactions (e.g., the hydrogen evolution reaction and corrosion reaction) on the metallic Zn anode, inadequate intrinsic electrical conductivity of MnO₂ cathodes (≈10⁻⁵ S·cm⁻¹), active material dissolution, and structural collapse. This review begins by systematically summarizing the prevailing theoretical models that describe the energy storage reactions in Zn-Mn batteries, categorizing them into the Zn²⁺ insertion/extraction model, the conversion reaction involving MnO_x dissolution–deposition, and the hybrid mechanism of H⁺/Zn²⁺ co-intercalation. Subsequently, we present a comprehensive discussion on Zn anode protection strategies, such as surface protective layer construction, 3D structure design, and electrolyte additive regulation. Furthermore, we focus on analyzing the performance optimization strategies for MnO₂ cathodes, covering key pathways including metal ion doping (e.g., introduction of heteroions such as Al³⁺ and Ni²⁺), defect engineering (oxygen vacancy/cation vacancy regulation), structural topology optimization (layered/tunnel-type structure design), and composite modification with high-conductivity substrates (e.g., carbon nanotubes and graphene). Therefore, this review aims to establish a theoretical foundation and offer practical guidance for advancing both fundamental research and practical engineering of Zn-manganese oxide secondary batteries. Full article

Electronic waste is becoming a growing global pollution issue due to short device lifespans and insufficient safe disposal methods. Hazardous metals like arsenic and mercury from electronic waste harm both the environment and human health. Recycling processes remain underdeveloped, requiring new eco-friendly solutions. This paper reports on the synthesis and properties of the cationic surfactants ammonium terthiophene (CTT) and 3,4-propylene-dioxythiophene (C-ProDOT), which may have potential use in organic electronics. Ecotoxicological tests showed no significant long-term toxicity and medium-to-high biodegradability, which are keys for environmental protection. These surfactants also displayed selective bacterial adhesion, making them candidates for bionic devices. Life cycle assessment revealed higher energy use and ecotoxicity for C-ProDOT than CTT, underscoring the need for sustainable chemical design. Full article

Biochar (BC), a carbonaceous material derived from biomass pyrolysis, exhibits a wide range of physicochemical properties, including a high cation exchange capacity, porosity, and specific surface area, which make it a highly valuable amendment for soil enhancement and environmental sustainability. As BC has shown strong potential to remediate soils, enhance their fertility, and increase crop productivity, it can successfully be used as a soil remediation factor. Additionally, it can play a critical role in carbon sequestration and climate change mitigation, revealing a high sorption capacity, multifunctionality, and long-term persistence in soils, where it can remain stable for hundreds to thousands of years. The present systematic review aims at presenting the dynamics of BC when incorporated into a soil system, focusing on its pH, water-holding capacity, aeration, microbiota, and carbon and nutrient availability across various case studies, particularly in acid, saline/sodic, and heavy metal-contaminated soils. Given the variability in BC performance, robust, long-term field-based research is essential to validate the current findings and support the development of targeted and sustainable biochar applications. Full article

Water pollution continues to pose a critical global challenge, largely due to the unregulated discharge of industrial, agricultural, and municipal effluents. Among emerging solutions, enzymatic bioremediation stands out as a sustainable and environmentally friendly approach, offering high specificity and efficiency under mild conditions. Nonetheless, the practical application of free enzymes is hindered by their inherent instability, poor reusability, and susceptibility to denaturation. To address these limitations, the immobilization of enzymes onto solid supports, particularly clay minerals, has garnered increasing attention. This review presents a detailed analysis of clay minerals as promising carriers for enzyme immobilization in wastewater treatment. It explores their classification, structural characteristics, and physicochemical properties, highlighting key advantages such as a large surface area, cation exchange capacity, and thermal stability. Functionalization techniques, including acid/base activation, intercalation, grafting, and pillaring, are discussed in terms of improving enzyme compatibility and catalytic performance. Various immobilization methods such as physical adsorption, covalent bonding, entrapment, crosslinking, and intercalation are critically evaluated with regard to enhancing enzyme activity, stability, and recyclability. Recent case studies demonstrate the effective removal of pollutants such as dyes, pharmaceuticals, and heavy metals using enzyme–clay composites. Despite these advances, challenges such as enzyme leaching, mass transfer resistance, and variability in clay composition persist. This review concludes by outlining future prospects, including the development of hybrid and magnetic clay-based systems and their integration into advanced water treatment technologies. Overall, enzyme immobilization on clay minerals represents a promising and scalable approach for the next generation of wastewater bioremediation strategies. Full article

This study introduces a novel nucleic acid testing (NAT) protocol that integrates rapid deoxyribonucleic acid (DNA) extraction, isothermal amplification, and visual detection to enable efficient analysis of opportunistic pathogens. Polyethylenimine-functionalized iron oxide (PEI-Fe₃O₄) nanoparticles were prepared by combining PEI, acting as a stabilizing agent, with iron salt, which was utilized as the metal ion precursor by the ultrasonication-assisted co-precipitation method, and characterized for structural, optical, and magnetic properties. PEI-Fe₃O₄ exhibited cationic and anionic behavior in response to pH variations, enhancing adaptability for DNA binding and release. PEI-Fe₃O₄ enabled efficient extraction of E. faecium DNA within 10 min at 40 °C, yielding 17.4 ng/µL and achieving an extraction efficiency of ~59% compared to a commercial kit (29.5 ng/µL). The extracted DNA was efficiently amplified by loop-mediated isothermal amplification (LAMP) at 65 °C for 45 min. Pyrogallol-rich poly(tannic acid)-stabilized gold nanoparticles (PTA-AuNPs) served as colorimetric probes for direct visual detection of the DNA amplified using LAMP. The magnetic-nanogold (PEI-Fe₃O₄/PTA-AuNPs) hybrid system achieved a limit of quantification of 1 fg/µL. To facilitate field deployment, smartphone-based RGB analysis enabled quantitative and equipment-free readouts. Overall, the PEI-Fe₃O₄/PTA-AuNPs hybrid system used in NAT offers a rapid, cost-effective, and portable solution for DNA detection, making the system suitable for microbial monitoring. Full article

The Nujiang region of Yunnan is by far the richest tourmaline-producing mining area in China. Since the discovery of the tourmaline-bearing deposit in Yunnan Province in 1980, there have been few comprehensive gemmological studies of this deposit. Therefore, the results of tests on 32 tourmaline samples from the Fugong and Gongshan regions of Yunnan are reported in this paper. The chemical composition of the Yunnan tourmalines was analyzed, and the contents of major trace elements were compared with those of tourmaline samples from different localities reported in the literature to highlight their specific provenance characteristics. Microscopic observation revealed the presence of liquid, gas, and solid inclusions; Raman spectra indicated the presence of constitutional water and CH₄-C₂H₆ dihydrate in the Yunnan tourmalines and also pointed to the influence pattern of the Fe content. The infrared spectrum in the range of 4000–4800 cm⁻¹ showed the frequency of metal cations and hydroxyl groups. Based on the characteristic peaks at 4343 cm⁻¹ and 4600 cm⁻¹, a quick distinction between elbaite and dravite could be made. UV–Vis absorption spectroscopy analysis showed that in yellow tourmalines, Mn²⁺-Ti⁴⁺ IVCT is the main cause of color, while green coloration occurs due to Fe²⁺–Fe³⁺ interactions or Cr³⁺ and V³⁺, and the pink color is caused by Mn³⁺ d-d transitions. The three-dimensional fluorescence spectra revealed the presence of the main fluorescence peaks at λex280/λem320 nm and λex265/λem510 nm in the tourmaline samples analyzed and the fluorescence intensity with Ti and Fe contents. Full article

Zeolitic imidazolate framework (ZIF)-8 materials exhibiting zinc metal centers partially replaced by cobalt or neodymium were successfully synthesized via a convenient coprecipitation method. The resulting materials were structurally and microstructurally characterized by SEM, XRD, FT-IR, and TGA, among other techniques. Subsequently, ZIF-8 nanoparticles were integrated into polyacrylonitrile fibers (PAN) via the electrospinning technique, followed by a secondary growth step to increase the ZIF-8 loading on the fiber’s surface. Furthermore, the characterization and evaluation of the materials’ CO₂ adsorption properties at low pressures revealed their volumetric CO₂ uptake capacities. The samples containing ZIF-8 powders modified with Co cations exhibited the best CO₂ capture performances of 26.48 and 8.08 cm³·g⁻¹ (at STP) for the unsupported and PAN-anchored materials, respectively. The strategy of seeding followed by secondary growth to anchor ZIF-8 onto PAN fibers is proposed as a novel and practical approach for adsorbent processing. Full article

Currently, lepidolite is considered an important natural alternative for obtaining lithium, given the difficulty in processing other species containing this metal. However, its mechanical preparation and beneficiation present considerable challenges and play a critical role in its efficient separation by flotation. This study explores the effect of particle size and dodecylamine concentration during flotation in a laboratory Denver cell. The results indicate that particle size significantly affects the finding in which the optimum was −90 + 75 μm, with a separation efficiency of 94%, and with only 2.067 × 10⁻⁵ M of dodecylamine (DDA) (5 g/t) at pH 11.0. The hydrophobicity of lepidolite was generated by the effect of the chemisorption of the cationic collector and the FTIR results indicate detection of the characteristic bands of the adsorption of DDA to the surface of lepidolite. Full article

The Long Interspersed Element-1 (L1) retrotransposon is an ancient genetic parasite that comprises a significant part of the human genome. ORF2p is a multifunctional enzyme with endonuclease (EN) and reverse transcriptase (RT) activities that mediate target-primed reverse transcription of RNA into DNA. Structural studies of LINE-1 ORF2p consistently show a single Mg²⁺ cation in the reverse transcriptase active site, conflicting with the common DNA polymerase mechanism which involves two divalent cations. We explored a reaction pathway of the DNA elongation based on the recent high-resolution ternary complex structure of the ORF2p. The combined quantum and molecular mechanics approach at the QM (PBE0-D3/6-31G**)/MM (CHARMM) level is employed for biased umbrella sampling molecular dynamics simulations followed by umbrella integration utilized to obtain the free energy profile. The nucleotidyl transfer reaction proceeds in a single step with a free energy barrier of 15.1 ± 0.8 kcal/mol, and 7.8 ± 1.2 kcal/mol product stabilization relative to reagents. Concerted nucleophilic attack by DNA O3′ and proton transfer to Asp703 occur without a second catalytic metal ion. Estimated rate constant ∼60 s⁻¹ aligns with RT kinetics, while analysis of the Laplacian of the electron density along the cleaving P-O bond identifies a dissociative mechanism. Full article