Dye Contaminants Research Articles

Cutting-Edge Applications of Cellulose-Based Membranes in Drug and Organic Contaminant Removal: Recent Advances and Innovations

The increasing environmental challenges caused by pharmaceutical waste, especially antibiotics and contaminants, necessitate sustainable solutions. Cellulose-based membranes are considered advanced tools and show great potential as effective materials for the removal of drugs and organic contaminants. This review introduces an environmentally friendly composite membrane for the elimination of antibiotics and dye contaminants from water and food, without the use of toxic additives. The potential of cellulose-based membranes in reducing the impact on water quality and promoting environmental sustainability is emphasized. Additionally, the benefits of using biobased cellulose membranes in membrane biological reactors for the removal of antibiotics from pharmaceutical waste and milk are explored, presenting an innovative approach to achieving a circular economy. This review provides recent and comprehensive insights into membrane bioreactor technology, making it a valuable resource for researchers seeking efficient methods to break down antibiotics in industrial wastewater, particularly in the pharmaceutical and dairy industries.

Synthesis and characterization of Selenicereus undatus extract mediated nano-Bi2O3 and its application in the adsorption of Rhodamine B dye

Betacyanins (BC) are reddish-purple pigments widely found in the peels of white-fleshed dragon fruit (Selenicereus undatus) and peels and pulps of red-fleshed dragon fruit (Selenicereus costaricensis). BC pigments are good anti-oxidants that inhibit the formation of reactive oxygen species (ROS) in plants and thereby promote the reduction of metal ions to zero-valent metals. It also acts as a good stabilizing and capping agent in the synthesis of nanoparticles. Hence, this research aims to extract, and quantize the content of BC from the peels of Selenicereus undatus, to fabricate betacyanin-rich- Selenicereus undatus (SU) modified bismuth oxide nanoparticles (Bi2O3 NPs) and characterize using UV-Vis, FTIR, XRD, SEM, EDAX, and BET. The quantity and stability of the betacyanin are optimized using various parameters like time, temperature, solvent ratio, pH, etc., through a UV-Vis spectrophotometer at 538 nm. Synthesized SU-Bi2O3 NPs aim to alleviate synthetic dye contaminants through adsorption- an efficient route for water remediation. The nano-adsorbent Bi2O3 NPs showed an increase in dye adsorption with an increase in reaction time, temperature, and Bi2O3 NPs dosage, enabling efficient removal of dyes such as Rhodamine B (RhB) dyes.

Robust regenerable metal-selenide-chitosan photocatalyst for the effective removal of Bromothymol Blue (BB) from wastewater

Water scarcity has been a crucial debate in recent years regarding the critical scenario of water pollution. The water body is continuously contaminated by organic effluents of textile industries, including pigmented dye pollutants. To tackle water bodies contamination, there is a need to develop an eco-friendly and efficient method for removing toxic dyes. Herein, ternary metal selenide nanocomposites of barium nickel selenide (NBSe-NPs) were synthesized by the solvothermal method supported by chitosan microsphere (NBSe-NPs-CM). Recovery of the catalyst was convenient by capping nanoparticles in the microsphere to maintain effective stability, biocompatibility, and well-designed surface coating. FTIR spectrum verified nanocomposite synthesis and chitosan microsphere (NBSe-CM) formation. SEM observations of nanocomposites and NBSe-CM indicated an average size of 13.78 nm and 253 μm, respectively. The presence of barium, nickel, and selenium elements in the NBS-NPs was verified by EDX analysis. The nanocomposites had a crystallite size of 15.73 nm. The photocatalyst exhibited a narrow bandgap of only 1.3 eV based on Tauc's plot. In addition, the synthesized microsphere demonstrated an efficient photocatalytic degradation (97 %) of Bromothymol Blue dye within 100 min under optimized operating conditions (pH of 6.0, dye concentration of 40 ppm, catalyst dosage of 0.25 g). The photocatalysis process followed the pseudo-first-order kinetics. The repeatability studies showed a slight decline in the catalyst's efficiency after four successive cycles. The DFT study shows that the NBSe-CM is energetically stable with more considerable negative binding energy, and the dye molecule interacts more strongly with the NBSe-CM surface. The findings highlight the exceptional characteristics of the newly designed ternary-metal-selenide-containing chitosan-microspheres for degrading dye contaminants from textile effluents.

Surface microstructure regulation of a novel N-CQDs /C3N4/Bi2WO6 self-cleaning synergistic photocatalytic degradation of NO coating

As well known, the apparent structure and chemical composition of self-cleaning photocatalytic coatings are crucial for their application. In this study, C3N4 with a large specific surface area was introduced into N-CQDs/Bi2WO6 to construct a highly catalytic active catalyst (CBW-0.5), which continuously degraded 57.7 % of NO. A robust self-cleaning photocatalytic coating (CCBW-B) was prepared by firmly bonding CBW-0.5 to the substrate through a layered spraying process. CBW-0.5 endowed CCBW-B with high catalytic activity, maintaining a degradation rate of 64.9 % for NO, and most of the surface organic dye contamination was degraded after 36 h. Due to the appropriate arrangement of low surface energy substances and micro/nano particles on the surface, CCBW-B with a graded cross network on the surface has contact angles (CA) of 156°/145° for water/olive oil, respectively. The influence of each component of CCBW-B on its photocatalytic and liquid repellent ability was studied, and the patterns for the differences in coating performance due to the changes in surface roughness structure caused by different layer distributions was discussed. In addition, the mechanism for the excellent performance of CCBW-B was explored using SEM, specific surface area, and the theory of the generation and distribution of air pockets. Finally, the durability and self-cleaning ability of CCBW-B were tested, and the synergistic mechanism of self-cleaning and photocatalysis was also provided.

A-056 Investigating Iodine Contrast Contamination in Cortisol and Aldosterone Samples

Abstract Background Primary aldosteronism (PA) is a condition characterized by hypertension resulting from excess secretion of aldosterone. PA caused by a unilateral aldosterone-producing adenoma can be treated with adrenalectomy but requires diagnosis by adrenal vein sampling (AVS). In this procedure, intravenous cosyntropin is administered to stimulate adrenal cortical secretion, followed by obtaining samples from the right and left adrenal veins and IVC. Laterization index is calculated by obtaining the aldosterone:cortisol ratio for each side, with a ratio cutoff ≥3 is used for confirmation. Iodinated contrast media facilitates visualization of catheter positioning during AVS and sometimes results in contamination of samples, evidenced by abnormal gel separator flotation (i.e. gel above plasma). This study had two aims: 1) to determine at what concentration contrast dye causes gel flotation and 2) discern whether contrast media interferes with our cortisol or aldosterone assays. Methods Gel flotation studies were performed by spiking pooled plasma samples with iohexol contrast media (Omnipaque 240, GE Healthcare) at concentrations ranging from 3%-10% v/v and aliquoting into fresh lithium heparin plasma separator tubes (BD, PSTs). Samples were then centrifuged and visually inspected for abnormal gel flotation. Contrast interference studies were performed using three pools of low (5 µg/dL), medium, (30 µg/dL), and high (55 µg/dL) cortisol concentrations. Sample pools were diluted with 20% contrast media or saline (control) and subsequently mixed at different ratios to create a range of dye concentrations (0.5%-18% v/v). Each mixture was assayed in triplicate for cortisol and aldosterone on a cobas e602 (Roche Diagnostics) and LIAISON XL (DiaSorin) immunoanalyzer, respectively. The total allowable error (TEa) was ±0.4 μg/dL or ±20% for cortisol and ±2 ng/dL or ±20% for aldosterone. Results Flotation of the gel separator was observed at a dye concentration of 4.5% v/v and greater. For the cortisol interference study, the bias was <5% for the three pools at all contrast media concentrations. Aldosterone was also measured in these pools, as bias could affect ratios calculated for PA. Aldosterone interference occurred at contrast dye concentrations ranging from 12%-20% v/v. An average positive bias of 34% was observed in aldosterone samples spiked with contrast media relative to the saline control. Compared to sample pool controls without added saline or dye, measurements for cortisol and aldosterone were 19%-22% and 16-25% lower in media- and saline-spiked samples (20% v/v), respectively, indicating a logical dilution effect. Conclusions Contrast dye contamination of AVS specimens can cause gel flotation in lithium heparin PSTs, preventing their analysis. The presence of contrast media at certain concentrations interfered with the DiaSorin aldosterone assay, leading to falsely elevated results. No cortisol assay interference occurred in the presence of contrast media but results were falsely decreased due to sample dilution. Samples collected during AVS may be contaminated with contrast dye causing gel flotation to occur. This is indicative of a minimum contrast media concentration of 4.5% v/v. Aldosterone:cortisol ratios may be inaccurate due to the positive aldosterone immunoassay bias with contrast media contamination. Care should be taken when reporting and interpreting AVS results with suspected contamination.

Photo-Fenton-like activity of Fe/ZnO structure applied as a heterogeneous catalyst for the methylene blue dye removal in aqueous matrices

This work developed efficient heterogeneous catalysts for the methylene blue (MB) dye degradation under photo-Fenton-like conditions. The material was modified to incorporate Fe(III) into ZnO, creating Fe/ZnO strucuture, and applied as heterogeneous catalysts at various pH levels. SEM analysis revealed an agglomerated and plate-like morphology of the synthesized catalysts. The enhanced structure facilitated a removal efficiency of 96.2% for MB dye when employing the photo-Fenton-based process using 5.0% Fe/ZnO catalyst. The high removal efficiency is attributed to the synergy between ≡Fe(III) and ≡Zn(II), which promotes the generation of photoradical species through the Fenton effect. Real water matrices served as a source of MB dye contamination, exhibiting minimal interference and achieving ∼100 % of removal. Scavenger studies indicate that •OH and e⁻ are the primary contributors to the high MB dye degradation efficiency. Additionally, the by-products formed after photo-Fenton process exhibit minimal toxicity towards Lactuca sativa L. No Fe(II) ions were leached at the end of the process. Eight cycles of degradation did not cause significant spectral changes in the FTIR analysis, as well as in the XRD patterns, indicating the material efficient and stable structure.

Removal of Dyes from Waste Water Using Low‐Cost Adsorbents

AbstractThe principal objective of this article is a thorough analysis of the usage of inexpensive adsorbents to eliminate dyes from different aquatic environments. Dyes, commonly employed in industries—textiles, pharmaceuticals, and food, pose a significant environmental concern due to their persistence and potential toxicity. In response, researchers have explored the efficacy of low‐cost adsorbents (LCAs) as sustainable and economical alternatives for dye elimination. An overview of the environmental effects of dye contamination and the difficulties in using traditional dye removal techniques is given at the outset of the paper. It then delves into the diverse range of LCAs, including agricultural by‐products, waste materials, and natural substances, that have shown promise in adsorbing and eliminating dye contaminants. Examples of such adsorbents include activated carbon (AC) derived from agricultural residues, bio‐adsorbents from various plant materials, and industrial by‐products with inherent adsorption properties. Key mechanisms involved in the adsorption process, such as surface chemistry, pore structure, and electrostatic interactions, are elucidated to offer a fundamental understanding of the sorption capabilities of these materials. This comprehensive review consolidates the current knowledge on dye removal utilizing LCAs, offering insights into the challenges, advancements, and future directions in this environmentally significant field. The findings underscore the potential of harnessing readily available, sustainable materials as effective sorbents for mitigating the adverse impacts of dye pollutants in aqueous systems. The adsorption capacity is comparable to supplementary adsorbents suggested for the removal of dyes. The widely accessible adsorption properties of basic and acidic dyes do not significantly differ from one another.

Polyelectrolyte modified Ag-nanosphere: A Practical Approach for Sensitive and Selective SERS-based Detection of Organic Dye Pollutants

This study presents a cost-effective method for fabricating surface-enhanced Raman spectroscopy (SERS) substrates using Ag-nanospheres (AgNS) capped with Poly(diallyldimethylammonium chloride) (PDADMAC) and poly(styrene sulfonate) (PSS). AgNS synthesis involves immersing Ag-nanocrystals in a nonaqueous solution, mixed with PEs in an aqueous solution via ultrasonic disturbance. Resulting aggregates form stable spherical assemblies with diameters ranging from 150 nm to 450 nm, and various characterization techniques, including scanning electron microscopy with energy-dispersive X-ray, UV-visible spectrophotometry, dynamic light scattering, and zeta potential analysis, were employed to analyze their fundamental chemical and physical properties. These qualified AgNSs serve as SERS substrates for sensitive and selective identification of charged organic dye contaminants, such as rhodamine 6G (R6G) and rose bengal (RB). Sensitivity assessments with the optimized quantities of either PDADMAC or PSS-capped AgNSs demonstrate successful detection down to concentrations of 10-14 M for RB and 4 x 10-13 M for R6G. The same SERS substrates also enable electrostatically driven selective detection even in analyte mixtures, and an additional variation of the SERS substrate comprising a complex of PDADMAC-capped and PSS-capped AgNSs exhibited distinct SERS spectra influenced by both positively and negatively charged analytes. Finally, successful detection of two oppositely charged pesticides was achieved through electrostatic attraction, so theses polyelectrolytes capped AgNS-based SERS substrate presents a promising avenue for efficiently and selectively detecting charged organic contaminants.

Eco-friendly synthesis of nano ferrites for effective dye degradation and enhanced antimicrobial protection

This study investigates the synthesis of cobalt and nickel ferrite NPs using Araucaria heterophylla resin as a bio- template and nitrate salts of cobalt, nickel, and iron as precursors.The resulting spinel systems exhibit efficient degradation of organic dyes, including methylene blue and rhodamine-B, and demonstrate excellent reusability. The NPs antibacterial efficacy against pathogenic bacteria, such as Staphylococcus aureus, Bacillus subtilis, Escherichia coli, and Salmonella paratyphi, was also evaluated. Comprehensive characterization of the nanomaterials was performed using FT-IR, XRD, SEM, TEM, EDX, and VSM techniques. Magnetic measurements revealed the ferromagnetic nature of cobalt ferrites and the superparamagnetic nature of nickel ferrites, with reduced saturation magnetization and coercivity compared to bulk materials due to the quantum size effect. The nano-formulated ferrites exhibited superior antibacterial activity, highlighting their potential for water treatment applications. This study underscores the importance of removing dye contaminants from wastewater before discharge into aquatic ecosystems.

Machine learning prediction of dye adsorption by hydrochar: Parameter optimization and experimental validation

In response to escalating global wastewater issues, particularly from dye contaminants, many studies have begun using hydrochar to adsorb dye from wastewater. However, the relationship between the preparation conditions of hydrochar, the properties of hydrochar, experimental conditions, types of dyes, and equilibrium adsorption capacity (Q) has not yet been fully explored. This study conducted a comprehensive assessment using twelve distinct ML models. The Gradient Boosting Regressor (GBR) model exhibited superior performance with R² (0.9629) and RMSE (0.1166) in the test dataset, marking it as the most effective among the evaluated models. Moreover, this study also proved the feasibility of the GBR model through stability testing and residual analysis. A feature importance analysis prioritized the variables as follows: experimental conditions (41.5 %), properties of hydrochar (26.0 %), preparation conditions (18.1 %), and type of dye (14.4 %). Meanwhile, experimental conditions (C0 > 30 mmol/g, pH > 8, and higher solvent temperatures) and hydrochar properties (the BET surface area > 2000 m²/g, an (O+N)/C molar ratio < 0.6, and an H/C molar ratio of approximately 0.06) show higher Q for dyes. Experimental validation of the GBR model confirmed its practical utility with a suitable predictive accuracy (R² = 0.8704). Moreover, the study developed a Python-based GUI that has integrated the best GBR models to facilitate researchers' ongoing application and improvement of this predictive model. This study not only underscores the efficacy of ML in enhancing the understanding of dye adsorption by hydrochar but also sets a precedent for future research on sustainable contaminants removal through bio-based adsorbents.

Efficient degradation of methylene blue at near neutral pH based on heterogeneous Fenton-like system catalyzed by Fe2O3/MnO2

The contamination of aquatic environments by organic dye contaminants in industrial wastewater has attracted widespread global attention. The heterogeneous Fenton-like process presents an attractive method for degrading dye pollutants, especially when such reactions are conducted under neutral pH. In this study, Fe2O3/MnO2 composite was employed as a novel heterogeneous catalyst for activating hydrogen peroxide (H2O2) to oxidize and subsequently degrade methylene blue (MB) under neutral pH. Multiple characterization results have confirmed the presence of MnO2 and Fe2O3 as the primary phases of the synthesized compound catalyst. Degradation experiments have demonstrated that the degradation efficiency of MB approaches 100% under the conditions of H2O2 concentration of 0.30% and Fe2O3/MnO2 amount of 0.888 g/L. Furthermore, the Fe2O3/MnO2 catalyst exhibits consistent and outstanding catalytic activity within a broad pH range from 5 to 9 benefiting from the strong interface interaction in Fe2O3/MnO2. The investigation into the kinetics of the Fenton-like reaction indicates that the catalytic degradation of MB by Fe2O3/MnO2 in conjunction with H2O2 follows pseudo-first-order kinetics. Moreover, supplementary scavenging experiments have demonstrated the crucial role played by hydroxyl radicals (·OH) in the catalytic oxidation mechanism of MB. This study offers a promising catalyst for the treatment of dye-containing wastewater under neutral pH condition.

Targeted and non-targeted identification of dye and chemical contaminants in Loji River, Indonesia using FT-ICR-MS

This study utilized liquid chromatography (LC) alongside Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS) to explore the dyes and chemical contaminants in Loji River, Indonesia. We tentatively identified a total of 655 contaminants at various confidence level, subsequently classifying them into 22 distinct categories. Of the 54 dyes we detected, 12 corresponded with entries in our specialized in-house database. These 12 dyes were further confirmed by reference standards, matching both retention time (RT) and MS/MS spectra. LC-FT-ICR MS data showed that dyes from printing batik and textile industries are key contributors to river pollution. Particularly noteworthy were two sample locations that displayed substantial contamination, predominantly from azoic and reactive dyes. Additionally, pharmaceuticals were identified as one of the most frequently occurring contaminants, underscoring the inadequacies in the area's sewage management. To corroborate these findings, we conducted physicochemical, phytotoxicity, and acute toxicity tests, all of which verified the harmful effects of the Loji River's water on both the local flora and human populations. Notably, water samples that tested positive for dye contamination exhibited elevated toxicity levels. To the best of our knowledge, this study is pioneering in its molecular-level investigation of dye contamination in Southeast Asian rivers. Our results accentuate the pressing need for both targeted and non-targeted screening methods to identify contaminants in the surface waters of developing nations.

Sub-nanometer size level regulation of biomimetic channels in porous membrane for high-capacity removal of toxic dye contaminants

Organic dyes are an important chemical with a market demand of millions of tons. However, their massive emissions, especially alkaline dye contaminants, have caused serious disruption of the ecosystem and even cancers. Inspired by bionic mass transfer, several amino acid fragments (carboxylic acid, γ-aminobutyric acid, and glutamic acid) are introduced into the 2.5 nm-pore size cavity through in-situ polymerization. The flexible amino acid chains facilitate the transport of guest molecules into the channels, accelerating their movement within the porous framework. These flexible chains are implanted into a 2.5 nm pore cavity, forming a 0.8–1.5 nano-meter-sized confinement space, bringing about the strong absorption capability for alkaline contaminants. Notably, LNU-74-glutamic acid achieves an ultra-fast absorption rate for toxic dye contaminants (4.74 g g−1h−1), as well as the highest capacity per unit area among all reported porous adsorbents, including porous carbons, metal–organic frameworks, porous polymers. After encapsulation in commercial polymer, the mixed-matrix membrane reveals (LNU-74-glutamic acid@MMM) a rejection rate greater than 98 % in various real water environments at permeation flux of ∼320 L m−2h−1, including strong acid/alkali, river water, and seawater.

Flexible roles of TiO2 in enhancing carrier separation for the high photocatalytic performance of water treatment under different spectrum sunlight

Construction of heterogeneous-photocatalysts is an effective mean for enhancing charge separation, however, the specific roles of the individual components have not been thoroughly explored. In this article, a heterogeneous-photocatalyst, TiO2/MoO3-x, was constructed, revealing that the two components, TiO2 and MoO3-x, play varying roles under different light spectra. Under full spectrum light, an S-scheme mechanism was achieved, which preserved the high oxidizing and reducing property of MoO3-x and TiO2, facilitating an augmented generation of reactive oxygen species (ROS). Under visible light, the MoO3-x functioned as the donor of hot electrons and the TiO2 served as the receptor platform for these electrons. The presence of the interfacial electric field enabled the transfer of hot electrons, leading to an enhanced ROS generation. Consequently, the TiO2/MoO3-x achieved high photocatalytic activity under both full spectrum and visible light. The optimized TiO2/MoO3-x catalyst demonstrated outstanding antibacterial efficacy, achieving eradication rates of 98.1 % for Staphylococcus aureus, and 99.6 % for Escherichia coli respectively. Additionally, it exhibited substantial degradation activity with a rate of 0.028 min−1 for Rhodamine B (50 mg/L). Furthermore, the TiO2/MoO3-x membrane removed approximately 81.2 % of bacteria from surface water, underscoring the potential of the designed membrane in water purification systems. This article explored the distinct roles and corresponding charge transfer mechanisms of the TiO2 and MoO3-x under full spectrum or visible light, offering innovative ideas for the design of full-spectrum photocatalysts with high efficiency. The straightforward design of membrane-based filtering device demonstrated wide applications for treating wastewater for the removal of dye and bacterial contamination.

Constructing p-n heterojunction in CoO@TiO2 photocatalytic material to enhance the performance of catalytic degradation of Rhodamine B

Traditional Fenton reactions suffer from slow reaction rates and energy wastage degrade dye contaminant. By constructing a heterojunction interface between quantum dots and titanium dioxide, a CoO@TiO2 photocatalyst is prepared to extend the photoresponse range to longer wavelengths. Under infrared light irradiation, RhB is degraded by over 97 % after 120 min. CoO@TiO2 possesses a large surface area, loaded with a substantial amount of quantum dots, forming a p-n heterojunction, significantly enhancing the photocatalytic rate. This study provides a new approach for the efficient preparation of photocatalysts for the degradation of organic dye pollutants.

A highly efficient and stable PtNi bimetallic nanoparticles modified on Mo2C decorated N-doped carbon flowers catalysts for the remediation of environmental pollutants

The unregulated discharge of nitroaromatics (NAs) and organic dye contaminants into aquatic ecosystems is a growing global concern, highlighting the urgent need for the development of effective wastewater treatment technology. In this study, we prepared Mo2C decorated on N- doped carbon flowers supported with PtNi bimetallic (PtxNiy@Mo2C/NCF) nanoparticles using the self-polymerization of dopamine and followed by the chemical reduction methods. These catalysts, with varying Pt:Ni ratios, were designed for the highly efficient catalytic reduction of NAs and rhodamine b (RhB) under the mild reaction conditions. The HR-TEM images confirmed the formation of spherical PtNi bimetallic NPs with an average diameter of 1.68 ± 0.6 nm. The prepared PtxNiy@Mo2C/NCF catalysts exhibited significantly higher catalytic efficiency for 4-nitrophenol (4-NP) reduction compared to their respective monometallic counterparts using NaBH4. Particularly, the Pt0.75Ni0.25@Mo2C/NCF catalyst showed superior catalytic activity with the apparent rate constant (kapp: 0.6703 min−1) and TOF (17.0 × 10−7 mol mg−1 min−1) and high recyclability over eight consecutive recycles. Furthermore, the Pt0.75Ni0.25@Mo2C/NCF catalyst also exhibited high catalytic activity for other NAs and RhB dye reduction with excellent yields. This enhanced catalytic activity of Pt0.75Ni0.25@Mo2C/NCF catalyst could be ascribed to the synergistic effect of the bimetallic systems, leading to more efficient reactions. Additional experiments were conducted on a fixed bed reactor to demonstrate that the Pt0.75Ni0.25@Mo2C/NCF catalyst effectively reduce both 4-NP and RhB dye over 15 successive runs. This work may pave the way for using PtxNiy@Mo2C/NCF catalysts in various wastewater treatment applications.

Green nanoarchitectonics Ce-Co₃O₄/BiVO₄ (p-n) heterojunction nanocomposite: Dual functionality for photodegradation of Congo red and supercapacitor applications

In this work, we synthesised a new Ce-doped Co₃O₄/BiVO₄ heterojunction photocatalyst by a green synthesis strategy utilizing Magnifera indica leaf extract for Co₃O₄ and a precipitation method for pure BiVO₄. X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), UV–Visible diffuse reflectance spectroscopy (UV-DRS), Brunauer-Emmett-Teller (BET) surface area analysis, field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry (CV) were used to investigate the material's structural, optical The Ce-Co₃O₄/BiVO₄ heterojunction decreased the band gap energy to 1.92 eV, resulting in increased visible light absorption. The photocatalytic activity of the developed heterojunction was evaluated by degrading the anionic dye Congo red (CR) under different circumstances such as pH, catalyst dose, dye concentration, and irradiation period. At pH 4, 98 % degradation was obtained using a dye concentration of 50 ppm, a catalyst dose of 40 mg, and 50 min of sun light exposure. High-resolution mass spectrometry (HR-MS) validated the effective degradation of CR and offered information on the potential degradation process. Kinetic investigations revealed that the photodegradation of CR followed a pseudo-first-order kinetic model. This study demonstrates the effectiveness of Ce-Co₃O₄/BiVO₄ heterojunctions in photocatalytic applications, namely for the removal of dye contaminants from wastewater using visible light. Furthermore, the heterojunction showed a substantial rise in specific capacitance, reaching 1353 F/g, 5.4 times that of pure Co3O4. The Nyquist plot displayed a smaller arc radius, indicating improved electrochemical characteristics and a possible application as a semiconductor. These results highlight the Ce-Co₃O₄/BiVO₄ heterojunction as a promising photocatalyst with outstanding dye degrading capabilities and increased electrochemical performance, appropriate for diverse environmental and energy storage applications.

Removal of Rhodamine B from water using natural clay: a study on adsorption kinetics, thermodynamics, and environmental impact

ABSTRACT This study investigates the adsorption capabilities of natural clay for the removal of Rhodamine B (RhB) from water, emphasising its potential as a cost-effective and sustainable solution for water treatment. The adsorption process was studied at three temperatures, focusing on kinetics, thermodynamics, and equilibrium. UV Vis spectrophotometry confirmed that natural clay achieved a remarkable RhB removal efficiency exceeding 97%. Factors such as initial concentration, adsorbent dosage, and temperature significantly influenced the adsorption efficiency. Thermodynamic analysis revealed negative Gibbs free energy values (−26.27, −27.50, and −28.80 kJ/mol) across the tested temperatures (14°C, 24°C, and 34°C), indicating the spontaneous and favourable nature of RhB adsorption onto clay surfaces, which is further enhanced by higher temperatures due to its endothermic nature. Equilibrium data fitting favoured the Freundlich isotherm model, suggesting heterogeneous adsorption, while kinetics were best described by the pseudo-second-order model. Optimal conditions for maximum RhB removal were identified as 40 minutes contact time, initial pH 3.71, and 0.5 grams of adsorbent. These findings underscore natural clay’s potential for large-scale water treatment applications, offering both environmental benefits and economic viability as a sustainable solution to mitigate industrial dye contamination in water sources.

CdS quantum dots modified two-dimensional MXene photocatalytic membrane for efficient removal of organic dyes from aquatic systems

MXene, a novel two-dimensional (2D) material, has been applied for the removal of dye molecules from wastewater; owing to its ability to stack into unique interlayer permeation channels. However, the narrow interlayer permeation channels of MXene limit its high permeability, and the dye contaminants tend to block the channels on the membrane surface as well as between the laminae. In view of this, CdS quantum dots (QDs) were incorporated with photocatalytic ability into the MXene channels, and the fabricated CdS QDs@MXene/PVDF photocatalytic composite membrane had high separation efficiency by using PVDF polymer as the support layer. The results manifested that; the CdS QDs were homogeneously dispersed in the MXene separation layer, and the introduction of CdS QDs optimized the interlayer permeation channels of MXene, with permeate flux of 502.6 L·m−2·h−1. The composite membrane exhibited an excellent removal of Congo red and Rhodamine B (CR and Rh B) dyes under the coupling of membrane separation and photocatalytic process, with the optimal removal ratio of 97.3 % for CR and 98.5 % for Rh B, respectively. Moreover, the CdS QDs endowed the membrane with self-cleaning ability, superior permeability and selectivity under five consecutive photocatalytic cycles, demonstrating the great in-situ resistance to contamination. After five intermittent cycles, the dye retention rate still exceeded 90 % and the permeate flux reached 388.0 L·m−2·h−1. This study provides an exceptional reference for quantum dots modified two-dimensional MXene membranes.

Carbonization of golden shower pods to high surface area biochar for decontamination of cationic dyes and regeneration study by gamma radiations

Detoxification of water resources is the need of the hour and a number of environment friendly materials are proposed by scientist to deal with water pollution issues. The present study deals with preparation and characterization of porous activated carbon from golden shower pods, a waste ligno-cellulosic biomass, for the removal of dye contaminants from aqueous solution. The synthesized material, golden shower biochar (GSBC) was characterized using various analytical techniques to confirm the presence of active sites. The BET analysis of GSBC revealed high surface area of 1120 m2/g with total pore volume of 1.099 cm3/g and average pore radius 19.618 Å. Operational parameters were optimized using batch studies by taking GSBC dose of 50 mg which showed complete removal of target dyes with an initial dye concentration of 200 mg/L with just 60 min interaction time; based on these results, a fixed bed column of GSBC was designed and column studies were performed. Adsorption isotherm studies were carried out using Langmuir and Freundlich models, of which Langmuir model was found to be best-fit with maximum adsorption capacities of 208.86 mg/g, 284.35 mg/g and 327.56 mg/g for Crystal violet, Brilliant green and Methylene blue dyes respectively. Analysis of kinetics and thermodynamics revealed that the best-fit model was pseudo second-order with spontaneous reaction course and exothermic nature. Regeneration was carried out using gamma irradiation of dye loaded GSBC, followed by leaching in alcohol. It was observed that a 30 KGy dose was just sufficient to completely degrade the dye on the adsorbent surface. GSBC has shown immense potential for eradication of dyes from water effluents and it is easily recovered with negligible loss in efficacy.