Cationic Dye Research Articles

Experimental and theoretical investigation on a viologen-based coordination polymer: Hydrochromism, solvatochromism, temperature dependent luminescence and selective adsorption and separation of cationic dye methylene blue

Experimental and theoretical investigation on a viologen-based coordination polymer: Hydrochromism, solvatochromism, temperature dependent luminescence and selective adsorption and separation of cationic dye methylene blue

Functionalized agro-waste for the sustainable remediation of malachite green from wastewater

Herein, a novel eco-friendly spent coffee grounds (SCG) impregnated guar gum adsorbents (SGH-x) were fabricated by using borax as the cross-linking agent. Several influences as borax dosage, initial dye concentration, pH, contact time, and temperature on the adsorption properties of SGH-x for Malachite Green (MG) were investigated. At a borax dosage of 0.9 wt%, the SGH-x possess maximum adsorption capacity of 921.84 mg/g towards MG and water swelling ratio of 2075 % owing to the presence of three-dimensional network structure and abundant hydroxyl groups. At pH= 10, the removal of MG by SGH-x is nearly 100 %. An increase of adsorption capacities with the molecular weight of cationic dyes followed the sequence as: Rhodamine B (RhB, 479.0 Da), Crystal violet (CV, 407.98 Da), and Basic red 9 (BR9, 323.82 Da) can be explained as the synergy between the pore filling and charge effect. Kinetic and isothermal studies revealed that the adsorption process of MG adhered to pseudo-second-order kinetic model and Freundlich isothermal model, suggesting a chemical adsorption on heterogeneous surfaces. Additionally, regeneration experiments showed SGH-x maintain high adsorption capacity (above 80 mg/g) of MG after three cycles. This study provided a feasible route to prepare biogradable and cost-effective adsorbents for water purification.

Hydrothermally synthesized Sr-doped In2S3 microspheres for efficient degradation of noxious RhB pollutants in visible light exposure

A series of SrxIn2-xS3 (x = 0, 2, 4, 6 and 8 mol%) microspheres have been prepared at 160°C using hydrothermal approach and examined the impact of Sr doping on its structural, morphological, optical and photocatalytic properties. Structural properties have been investigated using X-ray diffraction (XRD) with Rietveld refinement. Morphology and elemental composition have been analysed using Field emission scanning electron microscopy (FESEM) and Energy dispersive X-ray Spectroscopy (EDX), respectively. Optical band gap energy (Eg) has been determined using Diffuse reflectance Spectroscopy (DRS) and found to range between 2.15 eV to 2.07 eV. Photoluminescence (PL) emission spectra confirm a decrease in charge carrier recombination rate with Sr doping. The negative surface potential has been assessed by the Zeta analyzer, which indicates its suitability for the degradation of cationic dyes such as Rhodamine-B (RhB). Among the SrxIn2-xS3 microspheres, Sr0.04In1.96S3 demonstrated highest photocatalytic efficiency ∼98 % degradation of RhB pollutant (10 ppm) in 240 min. using 10 mg of catalyst per 100 ml. The adsorption kinetics in the presently studied samples obeys the pseudo 2nd order kinetic model. This study highlights the significant impact of Sr doping on the photocatalytic efficiency of SrxIn2-xS3 microspheres, offering promising applications in removal of RhB dye.

Novel magnetic metal ferrite-mango starch composite for the removal of dyes in single and ternary dye mixtures from aqueous solutions: kinetic and thermodynamic studies

ABSTRACT Magnetic metal ferrites attached to biowastes are proven to be promising adsorbents for the removal of dyes from water. Magnetic composites with biopolymers are gaining interest in the field of treatment of wastewater because of their selective nature, recyclability, low cost and environmental compatibility. In this work, Zinc ferrite composite with starch, extracted from mango seed kernel (ZFNMS) was synthesised. Characterisation techniques, such as FTIR, XRD, FESEM, BET, TGA and pHzpc, were used for the structural analysis of ZFNMS. ZFNMS was used to remove Methylene blue, Crystal violet and Brilliant green dyes in single and multiple (ternary) dye systems. The kinetics of adsorption by ZFNMS revealed that pseudo-second-order of kinetics was most appropriate for this study. Maximum adsorption capacities using ZFNMS for CV, BG and MB dyes were 142.9, 101.2 and 105.8 mg/g, respectively. The values of adsorption energies using ZFNMS were 200.5, 494.3 and 183.6 KJ/mol for CV, BG and MB dyes, respectively. Thermodynamic data revealed the spontaneous nature of the adsorption of dyes by ZFNMS and it was found that chemical adsorption was taking place in the present study. Regeneration of the adsorbent was done for successive five cycles and showed significant results. Thus ZFNMS is an ideal adsorbent for cationic dyes removal from water.

Transforming waste to purity: 3D electro-Fenton process boosted with pistachio shell-derived iron-biochar electrode for methyl violet 2B dye catalytic removal

Traditional degradation methods with typical catalysts which have limited negatively charged surfaces are not effectively degrade cationic dyes. A multi-functional iron-biochar was prepared from waste pistachio shells (Fe@PSB) that offers enhanced dye removal due to abundance of negatively charged sites for the degradation of the carcinogenic dye known as methyl violet 2B (MV 2B) in a cutting-edge three-dimensional electrochemical Fenton system (3DEF) with graphite (GP) cathode and Titanium (Ti) anode (3DEF-Ti/GP). Catalytic properties of Fe@PSB were explored for MV 2B dye degradation at broad acidic pH range. At optimum operating conditions of the current of 2.0A, pH 5.0, and Na2SO4 dose of 0.2M, nearly 98.8% of 10mg/L MV 2B dye removal was attained in 60min of electrolysis time. Commercial particle electrodes did not perform as well for the MV 2B dye degradation. The catalytic mechanism of 3DEF-Ti/GP system was investigated by quenching experiments which revealed that the hydroxyl radical (•OH) was responsible for the oxidation of dye molecules. Fe@PSB significantly performed up to four successful cycles. Liquid chromatography-mass spectrometry analysis revealed that de-methylation was the primary degradation pathway. This unique approach not only valorizes agricultural waste but also paving the way for greener environmental solutions.

Reaction parameter optimization and photocatalytic activity of graphitic carbon nitride for the degradation of anionic and cationic dyes: A study on environmental remediation

Reaction parameter optimization and photocatalytic activity of graphitic carbon nitride for the degradation of anionic and cationic dyes: A study on environmental remediation

THE COMBINATION OF WASTE PRODUCTS FROM CHITIN AND SAWDUST TO REMOVE ANIONIC AND CATIONIC DYES

The application of the immobilisation method – which consists of immobilising modified sawdust in a carrier, a chitosan gel – enabled the development of a new sorbent. By combining waste products from chitin and sawdust, the properties of both adsorbents were utilised. This paper evaluated the adsorption efficiency of four dyes – Reactive Yellow 84, Reactive Black 8, Basic Violet 10 and Basic Green 4 – on four adsorbents – chitin flakes, chitosan flakes, chitosan beads and sawdust immobilised in chitosan beads. The latter adsorbent showed good adsorption properties for both anionic and cationic dyes. The experimental results showed a relationship between the amount of adsorbed and desorbed dye and the type of adsorbent. Chitin flakes showed the lowest adsorption capacity, regardless of the type of dye. The immobilisation of modified sawdust in chitosan had a particularly positive effect on the binding efficiency of cationic dyes.

Zeolite-decorated black TiOx quantum dots for photocatalytic degradation of organic cationic dyes under LED light irradiation

Defect engineering is a promising strategy to reduce the band gap of semiconductors, enhancing their photocatalytic activity under visible light by introducing intra-bandgap energy states. Among the materials studied, oxygen-deficient black TiOx stands out due to its potential in photocatalytic reduction and hydrogen evolution. However, the valence band edge maximum (VBM) of TiOx is not thermodynamically favorable for the direct oxidation of water to hydroxyl radicals (H2O/•OH). Although the formation of extensive oxygen vacancies is necessary to extend the light absorption of black TiOx to longer wavelengths, a high density of oxygen vacancies (Ov) significantly shortens the diffusion length of charge carriers within the TiOx, leading to increased recombination of electrons and holes (e-/h+), thereby suppressing photocatalytic activity. To overcome these limitations, confining TiOx particles to the quantum dot (QD) size range and constructing heterojunctions with a secondary phase can substantially improve charge carrier separation and photocatalytic performance. In addition to engineering the electronic structure of composite photocatalysts, the preaccumulation of pollutants and their subsequent degradation is an effective strategy. This method decreases the distance between the adsorbed pollutant and the active sites for reactive oxygen species (ROSs) generation, enhancing the efficiency of the photocatalytic degradation process. In this study, we confined TiOx particles to the quantum dot size range by constructing a heterojunction with H-Beta zeolite, which contains defect-induced energy states within its wide band gap. This type of zeolite is particularly effective in adsorbing cationic azo dyes, facilitating pre-accumulation and degradation. The synthesized catalysts were extensively characterized using HRTEM to determine the average size of the TiOx particles and photoluminescence (PL) analysis to investigate charge carrier separation. Our results demonstrated that while TiOx alone showed negligible degradation efficiency, and no •OH were detected, the QD TiOx/Z4 composite achieved complete oxidation of CV by •OH, as confirmed by TOC analysis. The photocatalytic degradation mechanism was proposed based on these experimental findings. These insights could be of significant interest to researchers exploring defective semiconductors for photocatalytic oxidation of organic pollutants in the liquid phase under visible light (LED) irradiation.

Corn stalk decorated with magnetic graphene oxide as an efficient adsorbent for the removal of cationic dye from wastewater

In this study, an in situ immersion loading method is employed to introduce graphene oxide (GO) nanosheets and hollow copper ferrite nanospheres into the ordered porous structure of alkali-activated corn stalk (CS). This approach facilitates the construction of a novel magnetic three-dimensional composite sponge (GO/CS/CuFe2O4) utilized for the efficient removal of methylene blue (MB) and malachite green (MG) dyes from wastewater samples. In this hybrid adsorbent, the stacking of GO nanosheets is inhibited due to the ordered porous structure of CS, based on which GO nanosheets are well immobilized and dispersed. In addition, the hollow CuFe2O4 nanospheres and GO nanosheets support each other, further reducing the accumulation of GO, and increasing the specific surface area of the adsorbent. The engineered morphology of GO/CS/CuFe2O4 sponges supports the maximum exposure of the active adsorption sites to the dye solution, promoting the adsorption process. Microscopy and surface analyses show that GO/CS/CuFe2O4 sponges have a rich pore structure with the specific surface area of 289.85 m2·g−1, more than 17 times higher than that of CS, significantly improving their adsorption performance for MB and MG. The maximum adsorption capacity of GO/CS/CuFe2O4 for MB and MG is as high as 243.65 and 231.53 mg/g, respectively, superior to those of many other biomass-based adsorbents. The dye adsorption performance of GO/CS/CuFe2O4 can be well described by the Langmuir adsorption isotherm and pseudo-second-order kinetic model, suggesting the existence of strong monolayer chemisorption. The FTIR and X-ray photoelectron spectroscopy (XPS) analyses show that the dye removal mechanisms observed mainly includ π-π interactions, hydrogen bonding, electrostatic interactions and pore filling. In addition, GO/CS/CuFe2O4 sponges exhibit an excellent magnetic behavior (Ms = 49.52 emu/g), enabling the adsorbent to be recycled by the application of a magnetic field. The adsorption capacities of the adsorbent for MB and MG remain 88.6 % and 90.2 % of the initial adsorption capacity, respectively, even after 10 regeneration cycles, showing its excellent reusability performance. Finally, GO/CS/CuFe2O4 is applied for the removal of MB and MG from real aqueous environments comprising the seawater, tap water and wastewater treatment plant effluent, and the removal rates are observed to be over 90 % of that achieved in deionized water. This study provides new concepts for the sustainable utilization of agricultural waste and natural structure of plants to purify dye containing wastewater.

Modified PVDF ultrafiltration membrane with host–guest supramolecular trapping for efficient separation of multiple organic contaminants

In our modern lifestyle, the cocktail of organic pollutants from everyday items, such as hair dyes, cloth dyes, food colours, hair oils, cooking oils, and agricultural proteins, enters water streams through household pipelines. This unnoticed contamination, growing alarmingly, poses a serious challenge beyond the scope of conventional separation techniques, calling for a comprehensive solution. While membrane technology offers a promising solution, it grapples with persistent surface fouling issues. This study introduces a novel approach through the development of extraordinary Polyvinylidene fluoride-Montmorillonite-Cucurbit[6]uril (PVDF-M-CB[6]) mixed matrix membranes, presenting a potential breakthrough in overcoming surface fouling challenges and offering a versatile solution for the separation of an array of organic contaminants. Powered by the synergistic host–guest supramolecular complexation of CB[6] onto montmorillonite (M) clay support, these membranes demonstrate swift and selective encapsulation, leading to superior cationic dye rejection. Adding to the allure, CB[6]’s structure encourages favorable carbonyl interactions with bovine serum albumin (BSA), effectively repelling the protein away from the membrane, while also promoting seamless oil–water emulsion separation with an underwater oil contact angle of 150 ± 3°, displaying its superoleophobic nature and enhancing remarkable antifouling properties. The PV-M-CB[6] membranes showcased 2x removal of cationic dyes, 1.3x removal of anionic dyes, 1.4x oil–water emulsion separation, and 2x BSA separation compared to the pristine polyvinylidene fluoride (PVDF) membrane. These membranes displayed 98.3 % efficiency in oil–water emulsion separation and sustained a flux recovery ratio of over >75% after seven cycles. Overall, PV-M-CB[6] membranes represent an innovative solution with heightened hydrophilicity, remarkable antifouling performance, and exceptional proficiency in delivering one-stop organic foulant separation.

Use of white grape pomace for removal of cationic dyes from aqueous solution: kinetic, isotherm and thermodynamic characterization

Use of white grape pomace for removal of cationic dyes from aqueous solution: kinetic, isotherm and thermodynamic characterization

Elucidating antibiofilm as well as photocatalytic disinfection potential of green synthesized nanosilver against multi-drug-resistant bacteria and its photodegradation ability of cationic dyes

BackgroundBioinspired nanomaterials have widely been employed as suitable alternatives for controlling biofilm and pathogens due to their distinctive physico-chemical properties.MethodologyThis study explored the antibiofilm as well as photocatalytic potential of silver (Ag) nanoparticles (NPs) synthesized using the cell-free supernatant of Lactobacillus acidophilus for the disinfection of multi-drug-resistant (MDR) strains of enteroaggregative E. coli (EAEC), Salmonella Typhimurium, S. Enteritidis and methicillin-resistant Staphylococcus aureus (MRSA) on exposure to LED light. In addition, the removal of toxic cationic dyes i.e., methylene blue (MB), rhodamine B (RhB) and crystal violet (CV) was explored on exposure to sunlight, LED and UV lights.ResultsInitially, the synthesis of AgNPs was verified using UV- Vis spectroscopy, X-ray diffraction and transmission electron microscopy. The synthesized AgNPs exhibited MIC and MBC values of 7.80 and 15.625 µg/mL, respectively. The AgNPs exhibited significant inhibition (P < 0.001) in the biofilm-forming ability of all the tested MDR isolates. On exposure to LED light, the AgNPs could effectively eliminate all the tested MDR isolates in a dose-dependent manner. While performing photocatalytic assays, the degradation of RhB was observed to be quite slower than MB and CV irrespective of the tested light sources. Moreover, the sunlight as well as UV light exhibited better photodegradation capacity than LED light. Notwithstanding the light sources, RhB followed zero-order kinetics; however, MB and CV followed primarily second-order kinetics.ConclusionThe green synthesized AgNPs were found to be an effective photocatalytic as well as antifouling candidate that could be applied in therapeutics and wastewater treatment.

Simulated sunlight-driven photocatalytic activation of peroxydisulfate by core–shell Ag@SiO2/TiO2 nanocomposite for efficient methyl orange degradation

Herein, core–shell Ag@SiO2/TiO2 nanocomposites were synthesized and applied to activate peroxydisulfate (PDS) for wastewater purification. The Ag core and Ag-doped TiO2 shell were obtained by stober method and calcination method. The dispersion degree and size of Ag in TiO2 would influence the oxygen vacancy. Ag enhanced the visible absorption of TiO2 and activated PDS. Improved degradation performance was attributed to enhanced PDS activation by photogenerated e−, which separated h+and thus promoted methyl orange(MO) degradation. Reactive oxidative species were verified under dark and light conditions via quenching experiments and electron paramagnetic resonance tests, demonstrating SO4•–, h+, O2•–, and1O2were formed in light,whereasSO4•–, •OH, O2•–, and 1O2were responsible for MO degradation under dark conditions. The Ag@SiO2/TiO2/PDS/light system showed selectivity for removal of cationic dyes (e.g., methylene blue and malachite green) through adsorption and photocatalysis, whereas anionic dyes (e.g., MO) were degraded by photocatalysis alone. Besides, we found excess adsorption of micropollutant onto catalyst may be adverse to the activation of PDS. Therefore, the adsorption of oxidant (such as PDS) onto the catalyst surface would be beneficial for catalytic activation and micropollutant degradation, especially onto active sites. This work aims to provide a new avenue for core-shell structure catalyst synthesis in wastewater purification.

Poly(methyl methacrylate) functionalized graphene oxide/CuO as nanocomposite for efficient removal of dye pollutants

In this research, the use of a three-component nanocomposite of graphene oxide-methyl methacrylate and copper(II) oxide (PMMA-GO-CuO) was investigated. The aim of synthesizing this nanocomposite is to removal dye pollutants, specifically methylene blue (MB) and methyl orange (MO), which are commonly used in dyeing industries, through adsorption. The study focuses on creating GO-CuO and PMMA-GO-CuO nanocomposites as effective adsorbents. A simple and quick method led to the development of the PMMA-GO-CuO nanocomposite, which shows enhanced physical and chemical properties. Key materials include graphene oxide, methyl methacrylate, and copper(II) oxide nanoparticles. Characterization techniques such as FT-IR, XRD, SEM, and TGA were used to analyze the nanocomposite. Results indicate that dye adsorption is more effective at lower pH levels, suggesting that the PMMA-GO-CuO nanocomposite can efficiently remove dyes from industrial wastewater. The experimental data showed that the Langmuir isotherm model accurately represented the equilibrium adsorption, with maximum capacities of 285.71 mg g−1 for methylene blue and 256.41 mg g−1 for methyl orange, indicating a single layer of adsorption. The kinetics followed a pseudo-second order model, suggesting that the adsorption process involves chemical bonding. Additionally, thermodynamic parameters (ΔG°, ΔH°, and ΔS°) indicated that the adsorption is spontaneous. The adsorption mechanism involves hydrogen bonding, π-π interactions, and electrostatic interactions. This study investigates how factors like pH, temperature, contact time, and dye concentration affect the adsorption of methyl orange and methylene blue dyes. A PMMA-GO-CuO nanocomposite was used, achieving 84% removal of MB and 35% removal of MO from industrial wastewater. This study highlights the promising potential of PMMA-GO-CuO nanocomposite as an effective material for the removal of dye pollutants from industrial wastewater. The results showed that the graphene oxide in the composite is effective for removing cationic dyes due to its negative charge. Further research will focus on the optimization of the synthesis process with the aim of achieving competitive performance of this nanocomposite on a large scale. These findings not only advance the field of nanocomposite materials but also provide a practical solution to an important environmental issue, demonstrating the innovation of the present study in the literature.

The amalgamated impact of bimetals, amino groups, and cross-linked structures of MOF on MOF for the removal of cationic dyes

To protect the environment, it is important to develop effective materials/methods for eliminating or decomposing pollutants. Metal-organic frameworks (MOFs) have attracted considerable interest due to their special properties, including their exceptional porosity and customizable architecture, which make them highly adaptable for many applications. In this study, bimetallic (Ce/Zr) NH2-UiO-66@NH2-MIL-125 was prepared and characterized by, X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, thermogravimetric and BET analysis. The prepared bimetallic (Ce/Zr) NH2-UiO-66@NH2-MIL-125 served as a potent adsorbent for the efficient removal of cationic dyes via electrostatic, hydrogen bonding, ionic bonding, and π–π stacking. The adsorption of RhB and MB dyes by bimetallic (Ce/Zr) NH2-UiO-66@NH2-MIL-125 includes both isothermal and kinetic studies. The equilibrium adsorption data was found to conform to the Langmuir isotherm, whereas the kinetic adsorption process followed a pseudo-second-order model. The cross-linked structure of MOF on MOF enhances the stability of the adsorbent, and has the potential to efficiently adsorb and release organic dyes over multiple cycles. The aforementioned interactions as well as stability and reusability make the bimetallic (Ce/Zr) NH2-UiO-66@NH2-MIL-125 one of the most promising adsorbent for the removal of dyes from water.

Application of Anionic Hydrogels from Date Palm Waste for Dye Adsorption in Wastewater Treatment.

This work aimed to develop an anionic cellulose nanofiber (CNF) bio-adsorbent from date palm tree waste and to investigate its removal efficiency compared to cationic methylene blue dye from contaminated water. Date palm pulp was first prepared from date palm leaves through acid hydrolysis using H2SO4, followed by hydrolysis in a basic medium using KOH, in which the process completely removed the components of hemicellulose, lignin, and silica. To obtain anionic CNF, the resulting pulp was further treated with H2SO4, followed by centrifugation. Biogel formation of the CNF suspension was promoted by sonication, where its removal efficiency of methylene blue dye was studied as a function of dye concentration, temperature, contact time, and pH value. In this work, we investigated two isotherms, i.e., Langmuir and Freundlich. The Langmuir model's consistency with the experimental data suggests that the adsorption of methylene blue dye onto CNF is monolayer and surface-limited. The reported maximum removal efficiency of 5 mg/g at 60 °C indicates the optimal temperature for adsorption in this specific case. Additionally, a pseudo-second-order model and Elovich model were also utilized to obtain a better understanding of the adsorption mechanism, in which we found not just physical adsorption but also an indication of a chemical reaction occurring between methylene blue dye and CNF. According to the results, that pseudo-second-order model's consistency with the experimental data suggests that the adsorption of methylene blue (MB) onto CNF is rate-limiting step involving chemisorption between the two. The study reveals that CNF adsorbents derived from renewable natural waste sources such as date palm leaves can be effective in removing cationic contaminants such as methylene blue dye.

Surface charge alteration of charcoal derived from bamboo leaves and understanding the interaction with anionic and cationic dye

Cost-effective adsorbents derived from regenerative sources provide a sustainable solution to the pressing environmental pollution challenges. Conventional studies often rely on biochar-based adsorbents obtained at high carbonization temperatures in an induced environment. The present study explored the efficacy of carbon derived from the stems (CBS) and leaves (CBL) of bamboo plants as efficient dye adsorbents at low carbonization temperatures. CBL carbonized at 350 °C exhibited a remarkable dye adsorption efficiency of 90%, significantly outperforming CBS, which achieved only 39% efficiency. To enable the adsorption of both dyes, heterophase metal oxides, specifically Fe-doped ZnO and ZnFe2O4 were incorporated. Zeta potential measurements revealed a transition from negative to positive values with metal oxide incorporation, suggesting alterations in the surface acidity and functional group composition. The adsorption performance of the composite (WC20) sample was evaluated using Congo Red (CR) and Crystal Violet (CV) dyes. Comprehensive studies on the adsorption kinetics, isotherm modeling, and thermodynamics have been conducted to identify WC20 as the most effective composite. The equilibrium adsorption data aligned well with the Langmuir isotherm model, demonstrating maximum adsorption capacities of 65.31 mg g−1 for CR and 38.05 mg g−1 for CV at room temperature of 298 K with constant pH. Thermodynamic analysis indicated a hybrid adsorption mechanism, wherein CR adsorption was predominantly driven by chemisorption, whereas CV adsorption was governed by physisorption. Mechanistic insights have revealed that electrostatic interactions and π–π stacking play crucial roles in dye removal. These findings underscore the potential applicability of WC20 as a cost-effective and efficient adsorbent for the remediation of both cationic (CV) and anionic (CR) dyes in wastewater, highlighting its viability for future environmental management and pollution mitigation strategies.

Brazilian bentonite/MgO composites for adsorption of cationic and anionic dyes.

Industrial effluents, especially those containing dyes, have become the main cause of contamination of water resources. In this context, Brazilian bentonite/MgO composites, with excellent adsorptive properties, were prepared and investigated for their effectiveness in removing cationic and anionic dyes from aqueous solutions. The new adsorbents were obtained using Brazilian bentonites and MgO using the mechanochemical method followed by heat treatment (at 700°C for 4h). Different characterization techniques were used for the chemical, mineralogical, thermal, surface, and morphological analysis of the raw clays and the composites. The experimental adsorption isotherms were quantified under different conditions of initial concentration, contact time, pH, adsorbent dosage, and temperature variation to interpret the adsorption mechanism of the crystal violet (CV) and Congo red (CR) dyes. The modeling results were obtained from the empirical Sips equation and Pseudo Second Order (PSO) kinetics, indicating that the adsorption of molecules is a heterogeneous phenomenon that occurs in a monolayer on the surface (ns > 1), with the adsorption rate determined by chemisorption. The composites showed the best removal efficiency performance compared to the raw bentonites, with an increase of 12% for the CV dye and 46% for the CR dye. In addition, the qmax values obtained were 423.02mg/g and 479.86mg/g (AM01). This research underscores the potential of Brazilian bentonite/MgO composites as a promising solution for the removal of cationic and anionic dyes from water, offering hope for future applications in the field of environmental engineering and materials science.

Rich active sites ZIF-8 base on imidazole-based deep eutectic solvents for rapid adsorption of acid fuchsin and competitive adsorption

MimDES-ZIF-8 with rich active sites as positive charges and metal coordination sites were prepared based on imidazole based deep eutectic solvent (MimDES) using interface permeation method. 2-Methylimidazole (2-Mim) simultaneously acted as a hydrogen bond acceptor (HBA) in MimDES (hydrogen donner was 1,6-hexanediol) and an organic ligand in MimDES-ZIF-8, affecting the coordination of ZIF-8 during permeation. Four different zinc salt solutions (ZnCl2, Zn(NO3)2·6H2O, Zn(OAc)2·2H2O, ZnSO4·7H2O) were permeated into MimDES to obtain MimDES-ZIF-8 with different morphologies. All MimDES-ZIF-8 had higher Zn/N ration (>0.25), specific surface area and surface positive charges. The dye adsorption results indicated that MimDES-ZIF-8 showed high adsorption efficiencies for acid fuchsin (all exceeded 97.75 % under pH 7.5) and a fast adsorption rate (exceeding 93 % in 5 min and reaching equilibrium in 60 min). Among MimDES-ZIF-8, the adsorption capacity of ZIF-8-C was 4845.3 mg/g. After five cycles of adsorption, the AF removal efficiency of ZIF-8-C remained over 93.23 %. Moreover, ZIF-8-C also had good adsorption capacity for anionic dyes CR, cationic dyes MB and BB. The adsorption process aligned well with both the Langmuir model and the pseudo-second-order kinetic model. Based on FTIR, XPS, and electrostatic potential calculation, the adsorption mechanism was elucidated.

Removal process of an industrial dye using a biosorbent: characterization, kinetic, equilibrium, and thermodynamic studies

Adsorption-based removal is a highly efficient environmental phenomenon employed to eliminate various dyes, such as crystal violet (CV), which is prevalently used in the textile industry and subsequently discharged into natural ecosystems. This study aims to utilize natural bentonite clay sourced from Algeria for the extraction of cationic dye (CV) from wastewater. The characterization of the bentonite was conducted using Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), and X-Ray Diffraction (XRD). Evaluations assessed the impact of various parameters including pH, stirring time, temperature, and initial dye concentration on the adsorption efficiency. Optimal conditions for the maximal adsorption of CV were determined to be 430.18 mg g-1 at an adsorbent-to-dye solution ratio of 1 g L-1, pH 11.06, an equilibrium time of 40 minutes, and a temperature of 40°C. The adsorption kinetics were best described by the pseudo-second-order model, while the Freundlich isotherm model aptly described the adsorption isotherms. Thermodynamic parameters underscored the spontaneous and exothermic nature of the crystal violet removal process using raw bentonite. This research provides novel insights into the effective removal of a cationic dye from water and wastewater using Algerian bentonite clay.