Search Results (142)

Electrokinetic-Permeable Reactive Barrier (EK-PRB) technology can effectively remediate heavy metal-contaminated soil, and the properties of PRB materials play an important role in determining the remediation efficiency. To select a suitable PRB material, montmorillonite (MMT) was modified using cetyltrimethylammonium bromide (CTAB), sodium dodecylbenzenesulfonate (SDBS), and cocamidopropyl betaine (CAB), respectively; their remediation efficiencies for soils co-contaminated with Zn²⁺, Pb²⁺, and Cd²⁺ were then compared within an EK-PRB system. The results indicated that remediation efficacy varied significantly depending on the heavy metal and the surfactant used for modification. After 7 days of remediation, SDBS-modified MMT achieved the highest Zn²⁺ removal efficiency (49.65%), whereas CTAB-modified MMT showed optimal removal performance for both Pb²⁺ (38.03%) and Cd²⁺ (76.02%). When the remediation time was extended to 14 days, SDBS-modified MMT attained the highest removal efficiencies for Zn²⁺ (69.80%) and Pb²⁺ (69.50%), while CTAB-modified MMT maintained superior Cd²⁺ removal performance (86.94%). Energy consumption analysis showed that both CAB- and SDBS-modified MMT reduced energy consumption moderately compared with the unmodified control, whereas CTAB modification resulted in a substantial increase in energy demand. Experimental results confirm that surfactant-modified MMT effectively optimizes the EK-PRB remediation. A comprehensive evaluation considering both removal efficiency and energy consumption identified SDBS-MMT as the optimal material. The optimized EK-PRB parameters established in this study provide theoretical and technical support for the remediation of soils co-contaminated with multiple heavy metals. Full article

Biosurfactants offer a green, sustainable approach to many environmental bioremediations, especially for oil contamination. In this study, the aim is to evaluate the effectiveness of biosurfactants in accelerating hydrocarbon removal from mature fine tailings under anaerobic conditions. The bacteria were isolated from mature fine tailings and tested for biosurfactant production using different biosurfactant screening methods (i.e., blood agar, cetyltrimethylammonium bromide (CTAB) blue agar, oil displacement, and drop collapse). The most efficient strain showed high similarity to Stutzerimonas stutzeri by 16S rRNA gene sequencing. Results showed that this strain produces rhamnolipids with a critical micelle concentration (CMC) of 600 mg/L and a minimum surface tension of 38.70 ± 0.08 mN/m. Moreover, when supplemented with whey, the strain showed a high emulsification index of 24 toward toluene (66%) and hexane (60%). The bioremediation of mature fine tailings (MFTs) was conducted under anaerobic conditions by adding a consortium of the four strains that were positive in biosurfactant screening tests. The results showed 53% removal of n-alkane C9-C30 and a reduction in surface tension from 69 ± 0.5 mN/m to a minimum of 54.33 ± 0.5 mN/m. The results suggest the potential successful application of bioaugmentation for in situ biological treatment in the oil sands industry. Full article

This study investigates the adsorption of ibuprofen (IBU) and diclofenac sodium (DS) using bentonite modified with varying amounts (50, 75, and 100% of cation exchange capacity—CEC) of two surfactants: octadecyl(dimethylbenzyl)ammonium (ODMBA) chloride and hexadecyltrimethylammonium (HDTMA) bromide. The resulting organobentonites were characterized by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry/thermogravimetric analysis (DSC/TG), and zeta potential analysis. The results indicated that higher surfactant concentrations in organobentonites improved adsorption efficiencies for both drugs, while ODMBA-modified organobentonites exhibited notably larger adsorption capacities than HDTMA-modified samples. The adsorption isotherms fitted well to both the Langmuir and Freundlich models, with a better fit observed for the Freundlich model. The highest adsorption capacities were 102 mg/g for IBU and 160 mg/g for DS on sample OB-100 (organobentonite with 100% of ODMBA). Characterization of samples after drug adsorption, using FTIR, zeta potential and DSC/TG analysis, confirmed drug presence in organobentonites. Adsorption tests of DS in real river water (Danube and Sava rivers) showed that OB-100 demonstrated high removal capacity for DS. The findings suggest that organobentonites are low-cost adsorbents with potential for the removal of pharmaceutical contaminants from real aquatic environments. Full article

Yersinia enterocolitica is a foodborne pathogen that forms biofilms on surfaces, enhancing its survivability and increasing bacterial resistance, which poses a significant challenge to public health. Therefore, developing effective strategies to inhibit biofilm formation is crucial. Lipoic acid (LA) is a compound with antibiofilm properties. This study investigates the effects of LA on biofilm formation by Y. enterocolitica BNCC 108930 (a standard strain from the BeNa Culture Collection). Biofilm formation, maturation, removal, and cell viability were evaluated by crystal violet staining, extracellular polysaccharide assay, Methylthiazolyldiphenyl-tetrazolium bromide assays, motility, and quorum sensing (QS) assays. The results indicate that LA interferes with the early stages of biofilm formation by compromising cell membrane integrity and reducing cellular adhesion. Furthermore, 2.5 mg/mL of LA reduced biofilm biomass (with a 48 h treatment inhibition rate of 51.46 ± 1.29%) and extracellular polysaccharide production (with a relative inhibition rate of 30.09 ± 1.8%), while significantly reducing the metabolic activity of bacteria within the biofilm (inhibition rate over 85%) compared to the untreated group. Confocal laser scanning microscopy and field emission gun scanning electron microscopy confirm that LA induces a sparse biofilm structure, reduced aggregation, and decreased biofilm thickness to 21.33 ± 2.27 μm. Motility and QS assays demonstrate that LA affects flagellar motility and the secretion of N-acyl homoserine lactones. Transcriptome analysis revealed downregulation of genes involved in the QS system and biofilm formation (e.g., lsrA, lsrC, lsrD, lsrR, and oppA), as well as upregulation of genes related to bacterial chemotaxis and flagellar assembly (e.g., RS19655, RS15590, fliE, fliJ, fliP, fliA, and fliK). These alterations suggest that LA inhibits Y. enterocolitica biofilm formation by affecting intercellular communication and flagellar motility. This study highlights the antibiofilm properties of LA, providing a theoretical basis for potential applications in microbial and biofilm control. Full article

Millions of people across rural and peri-urban regions worldwide remain exposed to unsafe concentrations of naturally occurring fluoride in groundwater. In West Bengal, India, community-level water purification plants (CWPPs) have been widely installed to remove excess fluoride, yet their long-term operational performance remains minimally documented. This study assessed the pre-filter and post-filter water quality of 58 such groundwater-based CWPPs across the fluoride-affected districts of Bankura and Purulia in West Bengal, to evaluate in-field fluoride removal performance and potential hydrogeochemical, operational, and management drivers. Evaluation included fluoride concentration and key physicochemical parameters such as pH, temperature, electrical conductivity (EC), oxidation-reduction potential (ORP), total dissolved solids (TDS), and other anions including bromide, chloride, bicarbonate, nitrite, nitrate, phosphate, and sulphate. Fluoride concentration ranged from 1.7 mg/L to 8.2 mg/L and 1.6 mg/L to 3.9 mg/L in the sampled source water of Bankura and Purulia respectively, with both pre- and post-filter water of all the observed treatment units exceeding the WHO guideline of 1.5 mg/L. Potential contributors to underperformance may include inappropriate filter media selection, insufficient backwashing and regeneration, limited operational oversight and/or non-tailored treatment approaches. However, details on the adsorbent media and operational details were not available, and thus findings reflect observed field performance rather than necessarily causal relationships. These operational insights will contribute to the global discussion on improving decentralized groundwater treatment systems in resource-constrained settings. Full article

Soil harbors the highest concentration of microorganisms in ecosystems, and their molecular characterization through high-throughput sequencing is essential for metagenomic studies. However, obtaining high-quality, high-concentration DNA is limited by physicochemical properties (pH, heavy metals, humic acids) and adsorption to clay minerals. Although standardized commercial protocols exist, they present variable limitations depending on soil type. This study developed and validated the National Center for Genetic Resources—Microorganism Collection (CNRG-CM) method, which incorporates innovative pre-washing steps using phosphate-buffered saline (PBS) and sodium phosphate to effectively remove inhibitory humic acids and metal ions, combined with cetyltrimethylammonium bromide (CTAB)/chloroform extraction to achieve high-molecular-weight metagenomic DNA isolation. The CNRG-CM method was applied to three diverse soil types with variable physicochemical properties, recovering DNA concentrations ranging from 1000 to 1300 ng/μL ith a yield of 30 to 48 µg/g⁻¹, significantly exceeding those obtained with a standard commercial kit with maximum DNA concentrations of 360 ng/μL and a yield of 43 µg/g⁻¹. The CNRG-CM protocol is established as an effective and adaptable alternative for metagenomic DNA extraction across diverse agricultural and ecological contexts. It enables subsequent metagenomic studies of soil microbial communities. Full article

A carbon-modified attapulgite composite (C-AATP@CTAB) was synthesized via the hydrothermal method using citric acid as the carbon source and cetyltrimethylammonium bromide (CTAB) as a surface modifier for efficient rhodamine B (Rh-B) removal. Carbon modification elevated the composite’s specific surface area (212 m²/g) and negative surface charge (−38.21 mV), significantly enhancing dye adsorption capacity to 666.66 mg/g—nearly double that of unmodified ATP variants (360.4–386.8 mg/g). Kinetic studies confirmed pseudo-second-order adsorption kinetics, attributed to hydrogen bonding and van der Waals interactions between Rh-B and the composite. Under photo-Fenton conditions, C-AATP@CTAB achieved 99.8% Rh-B degradation within 20 min, demonstrating superior catalytic performance in heterogeneous Fenton/photo-Fenton systems. This work establishes a low-cost, high-efficiency adsorbent-catalyst hybrid derived from low-grade attapulgite, offering promising avenues for sustainable wastewater treatment. Full article

This study aimed to design a new composite with promising antimicrobial and antioxidant properties by a simple modification process of natural bentonite (B) with polysaccharide chitosan isolated from edible mushrooms Agaricus bisporus—ChM (sample B–ChM) and subsequently with a cationic surfactant—hexadecyltrimethylammonium bromide—HB (sample B–ChM–HB) for effective removal of mycotoxin zearalenone (ZEN). Characterization confirmed the presence of ChM in B–ChM and both ChM and HB in B–ChM–HB. Compared to non- or slightly inhibitory activity of B and B–ChM, B–ChM–HB showed fungicidal activity against yeast Candida albicans and mycotoxigenic mold Aspergillus flavus, with a reduction of 6.00 log10 (CFU/mL) and 5.32 log10 (CFU/mL), respectively. B–ChM–HB showed a very high neutralization ability on •DPPH (89.03%–95.99%) in the concentration range of 0.625–5.0 mg/mL, the highest ferrous ion chelating ability (80.25%) at a concentration of 0.625 mg/mL, and did not induce lipid peroxidation in the linoleic acid model system. While B and B–ChM exhibited low adsorption of ZEN, its adsorption by B–ChM–HB was significantly higher. The equilibrium results of B–ChM–HB for ZEN were in accordance with the linear isotherm model at pH 3 and 7, pointing out that hydrophobic interactions (partitioning process) were relevant for toxin adsorption by the composite. Similar maximum ZEN adsorbed amounts under the applied experimental conditions (14.4 mg/g) at both pH values suggested that its adsorption was independent of the pH. This study reported for the first time that a novel composite of B with ChM and HB showed promising antimicrobial and antioxidant properties and was an efficient adsorbent for mycotoxin ZEN. Full article

Organophilic acidic magadiites were prepared after an acidic magadiite (A-Mgd) reaction with cetyltrimethylammonium solutions containing different anions, such as cetyltrimethylammonium bromide (C16TMABr), cetyltrimethylammonium chloride (C16TMACl), and cetyltrimethylammonium hydroxide (C16TMAOH). The resulting materials were studied as adsorbents for Eosin Y removal from artificially contaminated solution. Successful preparation of oganophilic A-Mgd was achieved using C16TMAOH solution with an increased basal spacing from 1.21 nm to 3.15 nm and uptake C16TMA amount of 1.16 mmol/g. Meanwhile, no variation in the basal spacing of 1.20 nm occurred using C16TMACl and C16TMA Br solutions with an uptake mount of 0.07 to 0.09 mmol/g, respectively. Other techniques supported the behavior of the counteranion of surfactant solution on the synthesis of organophilic A-Mgd samples. 13C CP/MAS NMR data revealed that C16TMA cations displayed all-trans conformation comparable to C16TMABr solid, and ²⁹Si MAS NMR confirmed the stability of the host silicate layers during the reaction. The specific surface area of A-Mgd was reduced after the intercalation of C16TMA cations from 38 m²/g to 11 m²/g. The removal properties of organophilic samples were investigated under different conditions, including the Eosin Y pH solution, initial concentration, dosage mass, and content of C16TMA cations. The maximum removal amount was 70 mg/g at acidic pH and using A-Mgd prepared from C16TMAOH solution, while the other organophilic A-Mgds exhibited low removal amounts of 3 to 5 mg/g. The regeneration tests indicated that the efficiency was maintained after four reuse tests with a drop of 30 to 50% from the initial value after seven cycles. The adsorber batch design was employed to estimate theoretically the required masses of used samples to treat an effluent volume of 10 L at a removal percentage of 95% at a fixed initial concentration of 200 mg/L. In total, 20 g of organophilic prepared from A-Mgd and C16TMAOH solution was needed, while 243 g of sample prepared from C16TMABr solution was required. This study proposes the development of a cost-effective, sustainable solution for dye-contaminated wastewater treatment. Full article

Hydrothermal treatment has been demonstrated as a highly effective approach to enhance the adsorption properties of coal gangue (CG) for Cd²⁺ and Pb²⁺. This study evaluated the influence of NaOH concentration (X₁), hexadecyltrimethylammonium bromide dosage (X₂) and hydrothermal duration (X₃) on the modified CG’s composition and its adsorption capacities for Cd²⁺ (q_e,Cd) and Pb²⁺ (q_e,Pb). Response Surface Methodology (RSM) was utilized to explore the interactions among these variables, while XRD, SEM-EDX, FTIR and XPS techniques were employed to elucidate the adsorption mechanisms. The results reveal that hydrothermal treatment facilitated the formation of zeolite materials in the modified CG samples. Optimal conditions for Cd²⁺ adsorption (q_e,Cd = 58.4 mg/g) were determined as X₁ = 2.9 mol/L, X₂ = 1 g and X₃ = 16.8 h. For Pb²⁺ adsorption (q_e,Pb = 233.6 mg/g), the optimal conditions were X₁ = 2.4 mol/L, X₂ = 0.57 g and X₃ = 20.7 h. RSM analysis indicated that X₃ significantly influences q_e,Cd with the appropriate range of 14–18 h, while all three factors (X₁, X₂ and X₃) notably affect q_e,Pb, with suitable ranges identified as follows: X₁ = 1.8–3 mol/L, X₂ = 0.4–0.8 g and X₃ = 16–24 h. The primary adsorption mechanism for Cd²⁺ and Pb²⁺ was determined to be ion exchange, with additional Pb²⁺ removal achieved through the precipitation of cerussite (PbCO₃). Full article

Evaluation of characteristics and flocculation mechanisms of microbial flocculants facilitates the identification of potential applications and informs the fine-tuning of operational conditions for maximum activity. Therefore, this study aimed to characterise and optimise the operational conditions of bioflocculants produced from Klebsiella pneumoniae and Meyerozyma guilliermondii for potent wastewater treatment. Scanning electron microscopy, X-ray Diffraction (XRD), Thermogravimetric Analysis (TGA) and Fourier Transform Infrared Spectroscopy (FTIR) were employed to assess the surface morphology, crystalline structure, thermal stability, and functional group composition of the bioflocculants. Their cytotoxicity was assessed using the tetrazolium bromide-based assay against human colorectal adenocarcinoma (CaCO-2) cell lines. Flocculation efficiencies and mechanisms were determined using Jar and zeta potential assays, respectively. The bioflocculant from K. pneumoniae (Kp1) revealed a fibrous morphology, whereas that from M. guilliermondii (Mg1) displayed a granular structure. FTIR spectra revealed hydroxyl, amine, and alkene groups as key functional groups, while TGA analysis indicated that Kp1 was thermally unstable, contrary to Mg1, which exhibited good thermal stability. Bioflocculants Kp1 and Mg1 exhibited COD removal of 90.86% and 93.12% and turbidity reductions of 92.65% and 92.74%, respectively. Zeta potential analysis revealed that bioflocculant Kp1 primarily flocculated through charge neutralisation, while Mg1 employed a bridging mechanism. These bioflocculants illustrated strong potential to treat wastewater. However, the observed cytotoxic effect at increased concentrations warrants cautious handling and application in lower doses. Full article

This study investigates the adsorption of paracetamol from aqueous solutions using natural clinoptilolite and its modified forms. The raw zeolite (p-CLI) was converted into its protonic (H-CLI) and organo-modified (o-CLI) counterparts through ammonium exchange and calcination, and treatment with hexadecyltrimethylammonium bromide (HDTMA-Br), respectively. The materials were characterized by XRD, FT-IR, and SEM analyses. XRD confirmed that the clinoptilolite crystalline framework was preserved after both modifications, while FT-IR and SEM revealed partial removal of exchangeable cations in H-CLI and the formation of an HDTMA-derived organic layer on the external surface of o-CLI. Adsorption experiments were carried out under batch conditions at initial paracetamol concentrations of 0.5–10 mg/L, and equilibrium paracetamol concentrations were determined using differential pulse voltammetry (DPV). The raw clinoptilolite exhibited negligible adsorption capacity (<0.10 mg/g) due to its hydrophilic surface and microporous framework, which limit interaction with neutral organic molecules. Conversion to the protonic form slightly enhanced the adsorption performance (~0.15 mg/g), while HDTMA modification resulted in a modest additional increase (~0.25 mg/g), attributed to the formation of hydrophobic and organophilic surface sites. Overall, the results indicate that surface functionalization can improve the affinity of clinoptilolite toward weakly polar pharmaceuticals; however, the adsorption capacities remain limited. The novelty of this work lies in combining voltametric quantification with a direct comparison of proton-exchanged and surfactant-modified clinoptilolite to elucidate how specific structural and surface changes influence paracetamol uptake. Full article

For deep purification of wastewater containing anionic dyes. In this study, cetyltrimethylammonium bromide (CTAB)-modified geopolymer-based hectorite was synthesized via a steam-assisted method using depolymerized illite-based geopolymer as the silicon source and CTAB as the modifier, enhancing its adsorption performance for anionic dyes. The product was characterized by methods such as X-ray diffraction, and the effects of parameters such as adsorbent dosage and pH on the adsorption process were investigated. Adsorption experiments revealed that when the CTAB addition was 20%, the adsorption performance for Congo red was optimal (99.79%, 997.92 mg·g⁻¹), far superior to that of hectorite without CTAB (66.64%, 666.40 mg·g⁻¹). The adsorption process followed pseudo-second-order kinetics and the Langmuir isotherm model. Further comparison of changes before and after adsorption indicated that the adsorption mechanism primarily involved the combined effects of electrostatic interaction and hydrophobic effects. Additionally, after five adsorption–desorption cycles, the material maintained over 92% removal efficiency. By using different geopolymers as silicon sources to prepare CTAB-modified geopolymer-based hectorite, the high universality of this synthesis strategy was confirmed. This study provides a universal, green, and sustainable route for preparing efficient anionic dye adsorption materials and expands the high-value utilization of clay resources. Full article

The persistent pharmaceutical diclofenac (DCF) presents a significant environmental challenge due to its widespread presence and biological activity in water systems. This study aimed to develop and characterize a novel, low-cost biosorbent by modifying waste guava seeds (GS) with the cationic surfactant cetyltrimethylammonium bromide (CTAB) to enhance the removal of DCF from aqueous solutions. GS and seeds modified with CTAB at 2 mmol/L (MGS-2) and 10 mmol/L (MGS-10) were prepared and characterized using FTIR, SEM-EDS, TGA, and Zeta Potential measurements. Batch adsorption experiments were conducted to assess the effects of contact time, biosorbent dosage, and solution pH. CTAB modification changed the biosorbent’s surface charge from negative to positive, thereby enhancing DCF removal. The MGS-10 biosorbent demonstrated the fastest kinetics. Critically, an intermediate level of surfactant modification (MGS-2) proved optimal, achieving a maximum adsorption capacity of 38.0 mg/g at 45 °C. This capacity significantly surpassed both the GS (29.7 mg/g) and the MGS-10 (32.7 mg/g). This superior performance is attributed to a favorable multi-stage adsorption mechanism, which combines electrostatic attraction and hydrophobic interactions, and is determined to be an endothermic and entropy-driven process. While highly effective, the biosorbents showed poor regenerability with NaOH, indicating a need to explore alternative regeneration methods. This work demonstrates that optimally modified guava seeds are a promising and sustainable material for remediating pharmaceutical contaminants from water. Full article

Seismic attribute analysis, guided by well data, reveals widespread stratigraphic anomalies caused by erosion or karstification in the late Ordovician-early Devonian Hunton Group in the Arkoma Basin, eastern Oklahoma, USA. This study shows that these strata are more extensive than previously known. Well data and seismic mapping in the Red Oak petroleum field identify approximately 40 m thick Hunton lenses, averaging 3 km in diameter, surrounded by karsted rock. These lenses may be remnants of incomplete erosion during the Middle Devonian period (pre-Woodford unconformity) or result from Hunton rocks sagging into sinkholes caused by karstification and collapse of underlying Viola or Bromide carbonates. Using formation tops from wells, correlated with attribute and structure maps from a 3D seismic volume, we identify (1) areas lacking Hunton seismic markers, indicating complete removal; (2) areas with Hunton contacts, showing where Hunton remains; and (3) zones without Hunton but with a thin layer underlying carbonate strata, interpreted as an incipient karst zone, often near areas with Hunton. We also observe that the thickness of the overlying Woodford Shale, a key hydrocarbon target, correlates with karstic and erosional thinning of Hunton carbonates. Interpretation of 3D seismic data reveals a strong connection between thinned Hunton and thickened Woodford Shale. Full article