Lead contamination in wastewater is a significant environmental issue, necessitating effective removal methods. This study evaluates the performance of polyelectrolyte-enhanced ultrafiltration (PEUF) and nanofiltration (NF) processes for removing lead ions from aqueous solutions. The objective was to assess the effectiveness of various polyelectrolytes (chitosan, polyethylenimine, and polyacrylic acid) in conjunction with ultrafiltration and to investigate the influence of experimental parameters on lead retention and permeate flux.
RESULTS
In the PEUF process, a polyethersulfone membrane with a pore size of 10 kDa (PES10) was used. The maximum lead ion rejection of 97% was achieved with polyacrylic acid (PAA) at a concentration of 600 ppm and a transmembrane pressure of 4 bar. Increasing the feed pH enhanced lead retention but reduced permeate flux. Higher ionic strength negatively affected both lead retention and permeate flux. Over time, permeate flux decreased from 553 to 221 L/h/m2 due to solute accumulation and polymer aggregation. For the NF process, the maximum lead retention of 68% occurred at a transmembrane pressure of 6 bar. Lead retention increased at lower pH (73% at pH 2) but decreased at higher pH (47% at pH 5). The addition of salt adversely affected lead removal.
Dye sensitization is a promising approach to modify semiconductor photocatalysts. However, the use of synthetic dyes is neither cost-effective nor rational.
RESULTS
This research is the first report on the synthesis of colored nano-titanium dioxides as dye-sensitized photocatalysts via a convenient azo coupling reaction directly on the surface of n-TiO2-P25. According to their reduced band gap (2.6, 2.5, and 2.35 eV for dye-sensitized n-TiO2-P25 compared to 3.2 eV for bare n-TiO2-P25), dye-sensitized TiO2-P25 nanoparticles showed the absorption edge in the visible region, which expands their application compared to ultraviolet absorption in bare titanium dioxide. Various characterization techniques confirmed the structure and enhanced properties of the as-prepared nanoparticles, which were utilized as photocatalysts for the selective oxidation of benzyl alcohol to benzaldehyde in the presence of nitrate as an oxidant. These reactions were carried out under different wavelengths of visible light (blue LED, λ > 420 nm; green LED, λ > 510 nm; and red LED λ > 620 nm), yielded promising results, with reaction times of 19 h and significantly improved yields ranging from 80% to 20%, in comparison with the bare n-TiO2-P25. Furthermore, these photocatalysts are properly recyclable and reusable, addressing limitations of dye sensitization methods.
Duc Toan Ngo, Thi Trinh Thi Tran, The Luan Nguyen, Chau Ngoc Hoang, Tuyet-Mai Tran-Thuy, Thi Xuan Thi Luu, Tien Khoa Le
BACKGROUND
The development of environmentally friendly and efficient catalysts for pollutant reduction is a pressing need in green chemistry. Magnetic spinel ferrites, particularly CuFe2O4, are promising candidates due to their recoverability and tunable catalytic properties. However, conventional synthesis methods often require high temperatures and long durations.
RESULTS
Our study presents a green and rapid method for synthesizing CuFe2O4 nanoparticles as magnetically recoverable catalysts for the reduction of 4-nitroaniline at room temperature, using a coprecipitation–microwave treatment approach. The microwave-assisted synthesis enabled the formation of a well-crystallized cubic spinel phase without necessitating prolonged high-temperature calcination. The resulting materials were thoroughly characterized for their crystal structure, morphology, surface functional groups, elemental composition, specific surface area, porosity, and magnetic properties. Accordingly, the sample prepared without microwave treatment exhibited an amorphous structure, negligible magnetic response, and poor catalytic activity. In contrast, the microwave-treated samples, particularly those irradiated for 15–25 min, showed outstanding catalytic performance, achieving complete reduction of 4-nitroaniline to p-phenylenediamine in the presence of NaBH4 within 75–180 s, which are attributed to the enhanced spinel phase contents, increased surface concentrations of Cu2+ and Fe3+ ions, high porosity, and large specific surface areas. These catalysts also demonstrated strong magnetic properties, enabling easy magnetic separation and reuse.
Luciani de L Souza, Everton Skoronski, Fábio de Farias Neves
BACKGROUND
Wastewater produced from the thermal processing of poultry meat contains high levels of nitrogen and phosphorus. Thus, tertiary treatment is required to ensure that the wastewater meets Brazilian environmental regulations. Microalgae are capable of removing nutrients from wastewater and simultaneously synthesizing high-value biomolecules, such as proteins, which perform essential functions (structuring, energy reserve and bioactivity). However, microalgae are sensitive to temperature, which affects biomass productivity and the nutrient removal rate. The southern region of Brazil – where the present study was developed – has a temperate–subtropical climate, with periods of temperatures lower than 10 °C in winter, which may affect microalgal productivity and growth. The aim of the present study was to investigate the influence of temperature on nutrient removal from wastewater produced in a thermal poultry meat processing facility using a microalga-based process with Parachlorella kessleri. Biomass yield, nitrogen and orthophosphate removal efficiency and protein content were assessed at three temperatures (10, 20 and 30 °C) for 13 days.
RESULTS
A yield of 0.049 ± 0.01 g L−1 d−1 was obtained at 20 °C. On the sixth day of cultivation, the ammonia removal rate was 98.79%. Orthophosphate was removed efficiently in all treatments, with rates higher than 90%. Average protein concentration did not differ significantly among the treatments.
Mercury pollution from coal-fired flue gas poses significant threats to human health and the ecosystem, prompting strict control measures under international conventions like the Minamata Convention. Existing flue gas treatment technologies (e.g., dust removal, desulfurization) have limited mercury removal efficiency, while activated carbon injection suffers from high costs and secondary treatment issues. Graphitic carbon nitride (g-C3N4) shows potential for mercury removal, and doping copper (Cu) atoms can enhance its performance. This study aimed to synthesize a Cu-N4C catalyst via high-temperature calcination and explore its mercury removal mechanism in coal-fired flue gas.
RESULT
The Cu-N4C catalyst prepared at 800 °C showed remarkable mercury removal performance, with an average conversion of 98.50% at 50 °C and almost no Hg0 release, significantly outperforming conventional g-C3N4. It maintained high efficiency under various flue gas components, demonstrating strong resistance to interference from O2, CO2, NO, and SO2. Structural characterization by XRD and FTIR confirmed the high crystallinity of Cu-N4C and the impact of Cu doping on its chemical bonds, while SEM/EDX revealed a fluffy porous structure with uniform Cu distribution. N2 adsorption–desorption tests showed that Cu-N4C had a large specific surface area of 232 m2/g and a mesoporous structure, which enhanced the contact area with mercury. Mechanistic studies via Hg-TPD and XPS indicated that Cu+ in Cu-N4C was oxidized to Cu2+ during the reaction, forming a CuHg alloy with Hg0 to promote mercury removal through redox reactions and metal-mercury chemisorption.
Quorum sensing (QS) regulates several physiological behaviors in bacteria. Acyl homoserine lactones (AHLs) are self-synthesized auto-inducing molecules to form biofilm. Exogenous addition of AHLs can improve the bacterial community structure and biodegradation performance in wastewater treatment systems. However, the role of the QS-mediated interspecies interaction in phenanthrene degradation has been relatively less explored. There remains a notable research gap in understanding the effect of eavesdropping phenomena on biofilm formation, catabolic gene expression, and polycyclic aromatic hydrocarbon degradation in marine bacteria.
RESULTS
Two non-cognate AHLs – N-hexanoyl-dl-homoserine lactone (C6-HSL) and N-3-oxo-octanoyl-l-homoserine lactone (3OC8-HSL) – showed affinity for LasR and RhlR QS systems in a marine bacterium, Pseudomonas aeruginosa PFL-P1. Exogenous supplementation of AHLs improved the specific biofilm formation (SBF) index, cell surface hydrophobicity, cell auto-aggregation, and motility. Further, the phenanthrene degradation potential of the organism increased from 85.18% to 93.82% in the presence of C6-HSL and 96.59% in the presence of 3OC8-HSL within 5 days. The biofilm-associated extracellular polymeric substances (EPS) showed high emulsification activity towards several hydrocarbons. The high binding constant (4.42 L mol−1) and binding site number (1.38), indicating binding efficiency, suggested a strong interaction between EPS and phenanthrene. The exogenous addition of AHLs upregulated the expression of lasI, rhlI, and pslB. The phenanthrene catabolic gene, nahAc, was upregulated up to 3.07-fold (P < 0.01) in the presence of C6-HSL and up to 4.7-fold in the presence of 3OC8-HSL (P < 0.0001).
Tuo Wei, Rui Guo, Youxu Liu, Ruoxi Yan, Jianxun Yu, Le Qu, Gang Chen
BACKGROUND
Synergistic catalytic aquathermolysis represents a pivotal technology for heavy oil recovery, where the development, screening, and mechanistic understanding of composite catalysts play a central role. Although this approach demonstrates considerable scientific merit and practical utility, enhancing catalyst performance and economic viability remains an ongoing challenge.
RESULTS
In this study, a series of novel composite catalysts were designed and synthesized using piperazine as the ligand and Na-montmorillonite as the carrier and applied to the aquathermolysis reaction system of heavy oil. The experimental results show that the S@Ni(II)P composite catalyst exhibits excellent synergistic catalytic performance: the viscosity reduction rate reaches 67.5% compared with the untreated oil sample and 57.4% compared with the blank aquathermolysis sample, while maintaining good catalytic stability. The viscosity reduction performance of the catalyst was systematically verified by characterization techniques such as Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), elemental analysis, SARA analysis (saturates, aromatics, resins, asphaltenes), and gas chromatography (GC) of saturated hydrocarbons. In addition, based on the molecular structural characteristics of resins and asphaltenes in heavy oil, a model compound system was constructed in this study to deeply elucidate the synergistic catalytic mechanism of the S@Ni(II)P composite catalyst in the aquathermolysis process of heavy oil.
Evelyn Diane Pereira, Daniel Vianey Cardoso, Edson Antônio da Silva, Carina Contini Triques, Erica Camila Pavan, Kátia Andressa Santos, Ricardo Fiori Zara, Jaqueline Hoscheid, Márcia Regina Fagundes-Klen
BACKGROUND
In this study, lyophilized camu-camu (Myrciaria dubia) fruits were subjected to ultrasound-assisted extraction (UAE) using water, ammonia solution pH 9.5, and hexane. Each solvent was evaluated following a 23 factorial experimental design to assess the effects of amplitude, solvent-to-solid ratio, and temperature on extract yield and antioxidant potential. The results were compared to those obtained by the conventional method of dynamic maceration (DM). The UAE times were 20 min for water and ammonia solution pH 9.5, and 30 min for hexane.
RESULTS
The highest yield (47.78%) was reached with an amplitude of 90% for water, a solid-to-sample ratio of 22 mL g−1, and a temperature of 35 °C for water. On average, UAE yielded approximately 26% more extract than DM, requiring only one-tenth of the extraction time, resulting in significantly lower energy consumption. Although all extracts exhibited antioxidant activity, the aqueous extract showed the highest value (3056 μmol TE·g−1). Furthermore, it demonstrated stronger antimicrobial activity than ascorbic acid. High concentrations of ascorbic acid and phenolic compounds were also detected in the aqueous extract.
Electrically conductive membranes have recently emerged as a promising solution, offering self-cleaning properties with reduced fouling. In this study, we synthesized electrically conductive polyaniline (PANI) and carbon quantum dots-doped PANI (CQDs/PANI) using Piper longum plant extracts and incorporated them into polysulfone/polyvinylpyrrolidone (PSF/PVP) membranes for improved self-cleanliness by minimizing membrane fouling.
RESULTS
Optimized PANI and CQDs40/PANI (with 40% CQDs) achieved notable electrical conductance of 513.4 ± 24.1 and 997.3 ± 29.7 μS, respectively. The incorporation of 2% PANI and CQDs40/PANI into the membranes (denoted as PANI2-PVP2/PSF12.5 and CQDs40/PANI2-PVP2/PSF12.5) enhanced membrane conductivity to 4.23 × 10−3 and 5.30 × 10−3 S cm−1, respectively. The CQDs40/PANI modification improved hydrophilicity and porosity (16.0 ± 1.2% to 66.1 ± 2.7%). The water flux of PVP2/PSF12.5, PANI2-PVP2/PSF12.5 and CQDs40/PANI2-PVP2/PSF12.5 membranes was measured as 316.0 ± 9.3, 435.4 ± 11.9 and 485.7 ± 14.4 L m−2 h−1, respectively. Filtration of E. coli in phosphate buffer demonstrated significant fouling mitigation, with a reduced fouling from 69.1% to 49.3% and 34.5% for PANI- and CQDs40/PANI-modified membranes, respectively, and flux recovery improved correspondingly, from 46.4% to 74.4% and 83.7% along with improved E. coli rejection from 63.7 ± 3.3% to 83.1 ± 2.9% and 96.5 ± 1.5%, respectively. E. coli-spiked sewage water filtration showed superior E. coli rejection (98.3 ± 2.3%) and fouling recovery (86.3 ± 2.1%) with lower fluxes than that of E. coli. Hagen–Poiseuille and resistance-in-series models showed <15% variations in theoretical and experimental fluxes.
Bo Yu, Xiaoling Wan, Jiao Zhang, Juan Pei, Mingxing Guo, Siwei Xiang
BACKGROUND
Phosphate contamination in water bodies poses a significant threat to both human health and aquatic ecosystems. In this study, an MgAl layered double oxide (MgAl-LDO) was synthesized via calcination of MgAl layered double hydroxide for efficient phosphate removal from water.
RESULTS
MgAl-LDO exhibited an exceptional adsorption rate of 97% for phosphate and maintained an adsorption efficiency above 60% even after undergoing four regeneration cycles. The properties of MgAl-LDO were thoroughly analyzed by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and automated specific surface area. The adsorption mechanism of MgAl-LDO was investigated in conjunction with adsorption kinetics and isotherms, and was determined to be ion exchange.
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