Cationic Dye Research Articles

Polymeric Matrix of Modified Chitosan with Algae and Coal Fly Ash for a Toxic Cationic Dye Removal: Multivariable Optimization by Box-Behnken Design

Polymeric Matrix of Modified Chitosan with Algae and Coal Fly Ash for a Toxic Cationic Dye Removal: Multivariable Optimization by Box-Behnken Design

Magnetic and visible light-induced novel green synthesized magnetic Co3O4 photocatalysts via sunflower seed meal extract for anionic and cationic dye removal by adsorption assisted photocatalytic degradation

This study was aimed at the preparation of m-Co3O4 NPs (magnetic Co3O4 nanoparticles) from sunflower seed meal (SFSM) which is the waste of sunflower seed oil factories, and their application as a photocatalyst for the adsorption assistant photocatalysis degradation of methylene blue (MB), and direct yellow-50 (DY-50) under the visible irradiations. Also, the photocatalytic performance of m-Co3O4 NPs was evaluated in synthetic wastewater. The produced m-Co3O4 NPs were ferromagnetic with a saturation magnetization value of 4.3 emu g−1 and the degradation of cationic MB and anionic DY-50 dyes by 100% and 93% in 20 min and 35 min, respectively, by adsorption-assisted photocatalytic process under visible light was achieved. The reactions were found to be pseudo-second-order equation for the adsorption-assisted photocatalytic process for both dyes. The photocatalytic activity of m-Co3O4 NPs decreased slightly even after five repeated cycles. These results show that the m-Co3O4 NPs can be used successfully in dye treatment in wastewater with their adsorption-assisted photocatalytic properties, activation by visible light, magnetic separability, and low-cost production.

Rapid and efficient removal of water-soluble dyes via natural asphalt oxide as a new carbonaceous super adsorbent; NA-oxide synthesis and characterization

In this study, natural asphalt was oxidized to synthesize a new nano-structure adsorbent for dye removal. The functionalization of natural asphalt by oxidation introduced new properties that influenced its activity. The process of oxidizing natural asphalt with potassium permanganate resulted in a low-cost adsorbent, which can potentially be a more affordable option compared with synthetic alternatives. Characterization analysis confirmed the enhanced surface area, improving dye interaction and adsorption. The interconnected channels and capillaries of the oxidized natural asphalt facilitated the capillary action drawing in liquids, including dyes. The distinctive porosity of natural asphalt oxide (NA-oxide) was noted, and the experimental results showed that the NA–oxide nanoadsorbent efficiently adsorbed cationic and anionic dyes in water, with maximum capacities of 14.68 mg.g−1, 17.81 mg.g−1 and 16.47 mg.g−1 for methyl orange, methylene blue and Rhodamine B, respectively. The study investigated various parameters, such as concentration, adsorption dose, pH, contact time, and temperature, affecting the dye removal process. Langmuir, Freundlich, and Temkin isotherms along with pseudo-first and pseudo-second-order kinetic equations were applied to assess the adsorption process, indicating that dyes adhered to the pseudo-first-order model and Langmuir isotherm. Analysis of MO, MB, and RhB dyes revealed conformity to Langmuir isotherm and first-order kinetics. Thermodynamic evaluations like ΔH°, ΔS°, and ∆G° displayed the exothermic and spontaneous nature of dye adsorption on the NA-oxide adsorbent. Furthermore, the absorbent displayed remarkable stability with a recovery rate of 98.45% after ten cycles, signifying its potential for enduring effectiveness in dye removal processes.

MITOCHONDRIAL MEMBRANE POTENTIAL IS A FUNCTIONALLY RELEVANT AXIS OF NON-GENETIC CELLULAR HETEROGENEITY IN GLIOBLASTOMA

Abstract AIMS Glioma stem cells (GSCs) are believed to underpin treatment resistance in glioblastoma by virtue of their self- renewal capabilities and presumed transcriptional plasticity. Understanding how cell state diversity is established and maintained is crucial to make therapeutic gains. We have previously shown mitochondrial membrane potential (MMP) to be a functionally relevant source of extrinsic noise in embryonic and haematopoietic stem cells. This study evaluates cellular MMP as an axis of variability in GSCs. METHOD MMP was measured by flow cytometry in patient-derived GSC lines using cationic dyes that diffuse reversibly across the mitochondrial membrane in a voltage dependent manner. MMP-high and low populations (top and bottom 10-20%) were fractionated and subjected to RNA-sequencing and assays of proliferation and clonogenicity. Correlation between MMP and global transcription rate was investigated through a uridine analogue (5-EU) incorporation assay. The relationship between MMP and quiescence was assessed, with quiescence defined as inducible histone2B-GFP label retention after 10 days. Timecourse data for MMP was obtained through sequential staining. RESULTS RNA sequencing identified differential gene expression and exon utilization according to MMP status. MMP- high cells upregulated cell cycle genes, while MMP-low cells exhibited a diverse signature suggestive of a more differentiated state. A greater proportion of MMP-high cells were in cycle, but MMP-low cells formed more colonies. MMP positively correlated with global transcription rate in both cycling and quiescent GSCs. Time- course experiments revealed dynamic periodicity in cellular MMP. CONCLUSION The MMP axis reveals transcriptional and functional heterogeneity in GSCs and importantly unmasks phenotypic variability within the treatment-refractory quiescent compartment. The positive correlation between MMP and transcription rate, along with splicing differences, suggests a mechanism underlying functional diversity. Given the oscillatory dynamics of MMP, we postulate that stable-low MMP may define a deeply quiescent, therapy-resistant state. Evaluating MMP as a tractable regulator of GSC fate is warranted.

Effect of iron doping on nickel aluminate photocatalytic activity towards the degradation of methylene blue under visible and UV light

The major issue that industries have is the degradation of organic dye in wastewater. In this study, we introduce an iron-doped spinel-type photocatalyst for dye degradation. Due to advantages like a lower band gap, and favorable magnetic characteristics, iron-doped nickel aluminate can be a viable catalyst for dye degradation. Nickel aluminate and iron-doped Nickel aluminate NiAl2-xFexO4 (x = 0.05, 0.1, 0.5, and 1.0) were synthesized by the sol-gel method using citric acid as a capping agent. The obtained samples were calcined at 800 °C for 4 h. The spinel was characterized using X-ray diffraction (XRD) which helped in the identification of the purity of the phase and the calculation of the average crystallite size. Fourier Transform Infrared (FT-IR) spectra confirmed the presence of iron in the octahedral site; (SEM-EDAX) Scanning Electron Microscopy facilitated the surface morphology and Energy-Dispersive X-ray analysis provided the elemental confirmation and UV-DRS techniques assisted in the calculation of the band gap using the Tauc plot method. Photocatalytic efficiency was investigated against the cationic dye Methylene blue under UV and Visible light. The results showed degradation of 94.25% under UV light and 83.51% under visible light in 90 min and 150 min respectively using iron-doped nickel aluminate.

EDTA‐modified cellulose from sago bark (Metroxylon sagu) for anionic and cationic dyes removal

AbstractThe present research employed ethylenediaminetetraacetic (EDTA) modified cellulose to remove basic violet 10 (BV10) and reactive orange 16 (RO16) dyes. The cellulose was obtained from sago bark which was solid waste of sago starch industries. Sago bark contains 56.86% cellulose so that it can provide significant amount of active site. The optimum condition was examined using batch method investigating some parameters including pH, initial dye concentration, contact time, and thermodynamics. The adsorption capacity of cellulose (Cell) itself was also investigated for the comparison. The characterization of adsorbent showed the presence of ester bond, amine groups and escalating of surface area and pores after EDTA modification. The adsorption capacity of EDTA‐modified cellulose (Cell‐EDTA) was 73.53 mg/g for BV10 and 22.42 mg/g for RO16. The adsorption of both dyes onto Cell‐EDTA followed Langmuir isotherm model and pseudo‐second‐order kinetic model. Thermodynamic parameters indicated that the adsorption process was spontaneous, endothermic and feasible. Desorption studies proved that NaOH was an effective desorbing agent of BV10 and RO16. Based on research, Cell‐EDTA was more favorable in cationic dye, basic violet 10 than anionic dye, reactive orange 16.

Physiological and biomolecular interventions in the bio-decolorization of Methylene blue dye by Salvinia molesta D. Mitch

Methylene blue, a cationic dye as a pollutant is discharged from industrial effluent into aquatic bodies. The dye is biomagnified through the food chain and is detrimental to the sustainability of aquatic flora. Despite of number of physico-chemical techniques of dye removal, the use of aquatic flora for bio-adsorption is encouraged. Thus, we used Salvinia molesta D. Mitch in bio-reduction of methylene blue on concentrations of 0, 10, 20, and 30 mg L−1 through 5 days with biosorption kinetics. The dye removal was concentration-dependent, maximized at 2 days with 30 mg L−1 which altered the relative growth rate (44%) of plants. Biosorption recorded 71% capacity at optimum pH (8.0), 24 h reducing major bond energies of amide, hydroxyl groups, etc. Bioaccumulation of dye changed potassium content (446%) under maximum dye concentration modifying tissues for dye sequestration. Reactive oxygen species were altered on dye reduction by oxidase (33%) with redox homeostasis by enzymes. Plants altered the metabolism with over accumulation of polyamines (51%), abscisic acids (448%), and phosphoenolpyruvate carboxylase (83%) on dye reduction. Thus, this study is rationalized with a sustainable approach where aquatic ecosystems can be decontaminated from dye toxicity with the exercise of bioresources like Salvinia molesta D. Mitch as herein.

Development of a Fully Bio-based, Higly Efficient Polymeric Adsorbent Via UV Curing for Removal of Cationic Dyes

Development of a Fully Bio-based, Higly Efficient Polymeric Adsorbent Via UV Curing for Removal of Cationic Dyes

Phyto-mediated synthesis of ZnO nanoparticles and their sunlight-driven photocatalytic degradation of cationic and anionic dyes

Abstract In this study, zinc oxide-based nanocatalysts were biosynthesized using Ocimum basilicum (OB) and Olea africana (OA) leaf aqueous extracts, termed OB-ZnO and OA-ZnO, as a simple, affordable, and environmentally friendly approach. Their characteristics and efficacy in photodegrading cationic dyes (crystal violet and methylene blue) and anionic dyes (methyl orange and naphthol blue black) were investigated. The catalyst’s properties were analyzed using various techniques, including Fourier transform infrared, X-ray diffraction, photoluminescence, thermogravimetric analysis, UV-Vis, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and Brunauer–Emmett–Teller. Analysis revealed pure products having a hexagonal wurtzite structure, crystallite sizes of 15.04 and 21.46 nm, surface areas of 23.65 and 7.97 m2/g, particle sizes of 35 and 170 nm with spherical (uniform) and oval-like (non-uniform) shapes, and optical bandgaps of 3.15 and 3.05 eV, respectively. Photocatalytic applications under sunlight indicated excellent activity of both catalysts against targeted cationic and anionic dyes. Most notably, even though OA-ZnO has a lower surface area than OB-ZnO, it demonstrated greater efficiency. The variation in effectiveness is explained by the lower bandgap value of OA-ZnO and its ability to reduce electron–hole recombination due to its larger crystal size, which accelerates the degradation process. Additionally, both catalysts exhibited high stability after being used four times.

Selective adsorption of cationic dye by κ-carrageenan-potato starch bio-hydrogel: Kinetics, isotherm, and thermodynamic studies

An eco-friendly κ-carrageenan/potato starch bio-hydrogel is designed for the efficient removal of methylene blue (MB) dye from water. The incorporation of potato starch was successfully confirmed through XRD, FT-IR, and SEM analysis, while TGA highlighted the hydrogel's thermal stability. Batch adsorption experiments demonstrated excellent MB removal efficiency, with a maximum adsorption capacity of 116.1 mg/g under optimal conditions (initial dye concentration: 100 mg/L, contact time: 180 min, temperature: 20 °C, adsorbent dosage: 1.6 g/L, and pH: 11). FT-IR analysis indicated that electrostatic interactions and hydrogen bonding primarily govern the adsorption process. The adsorption followed pseudo-second-order kinetics and fitted well with the Langmuir isotherm model. Thermodynamic studies revealed that the adsorption was exothermic and spontaneous. A key feature of this bio hydrogel is its selective affinity for the cationic dye MB, in a mixture with Acid Orange (AO) and other cationic dyes (Rhodamine B (Rh B) and crystal violet (CV)). The adsorbent also demonstrated impressive reusability, maintaining 93 % of its efficiency after five cycles, highlighting its potential for sustainable and cost-effective water treatment.

Adsorption technique using new semi-IPN hydrogels for high removal of methylene blue dye from aqueous solutions

ABSTRACT Six new semi-IPN hydrogels using 2-acrylamido-methylpropane-1-sulfonic acid (AMPS) and Gelatin at different ratios through redox polymerization were prepared. Methylene-bisacrylamide and glutaraldehyde were used as the crosslinking agents for AMPS and Gelatin, respectively. The hydrogels’ swelling ratios and surface morphologies were analyzed using SEM for characterization. Porosity and specific surface area using the Brunauer–Emmett–Teller technique. DSC and Tg were also used for the thermal analysis of the prepared hydrogels, which show trans-glass temperature (Tg) higher than their raw materials AMPS and Gelatin. The prepared hydrogels were used to eliminate the cationic dye MB from the water-based solutions with an initial concentration of 600 ppm. The study discovered that the N9 and N10 hydrogels were extremely effective at removing a certain dye from aqueous solutions with an optimum pH level of 11 and an optimum temperature of 65°C. Both N9 and N10 achieved high removal efficiencies, reaching equilibrium at 90 min, whereas the other hydrogels required 120 min. N9 performed slightly better at 1078.919 mg/g and N10 at 1057.404 mg/g. The adsorption behavior of the two hydrogels followed the Langmuir model. The hydrogels exhibited pseudo-second-order kinetics. The thermodynamic study cleared that the adsorption of MB dye was endothermic and spontaneous. Results also showed that the adsorption of dyes with hydrogels N9 and N10 is chemisorption in nature. Desorption studies were conducted using 0.1 M HCl and NaOH. HCl was found to be the best eluent for dye recovery.

Advanced nano modification of ecofriendly glauconite clay for high efficiency methylene blue dye adsorption

This research focuses on the utilization of nano glauconite clay as an environmentally friendly sorbent for the removal of cationic dyes, particularly Methylene Blue (MB), from polluted water. The glauconite clay was sourced from the El Gidida region of Egypt and subjected to grinding in a laboratory-type ball mill to ensure homogeneity and increase the active sites available for the adsorption process. The resulting ball milled nano clay (BMNC) was characterized using techniques such as X-ray fluorescence (XRF), Fourier transform infrared (FT-IR) spectroscopy, transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). The concentration of MB dye was monitored using UV–Vis spectroscopy to assess the adsorption capacity of BMNC under various conditions including pH, time, dose, and temperature. The optimal conditions for the adsorption process were determined to be a pH range of 7–8, a contact time of 60 min, and a dose of 200 ppm, resulting in an adsorption capacity of 128 mg/g. This process demonstrated both low cost and high speed. The adsorption mechanism of MB on the BMNC surface was evaluated through kinetics, adsorption isotherms, and thermodynamics. The experimental data indicated an endothermic, spontaneous, and thermodynamically favourable adsorption process, which was further supported by simulated modelling results using Forcite program. The in-silico data aligned well with the experimental findings. Additionally, the study assessed the interference of salts, metal ions, and other dyes on MB adsorption onto BMNC, showing promising results. These findings strongly support the effectiveness of our sorbent substrate under challenging conditions.

Adsorption behavior of cationic dyes on starch nanocrystals: Kinetic, isotherm, and thermodynamic insights from single to multi-component systems

The adsorptive potential of starch nanocrystals (SNCs) was evaluated for the elimination of methylene blue (MB), crystal violet (CV), and malachite green (MG) from aqueous media in single, binary, and ternary dye systems using batch mode experiments. SNCs were extracted using mild acid hydrolysis to remove the amorphous parts of native granular starch, and they were characterized using different physicochemical methods, such as FESEM, XRD, FTIR, BET, TGA, and pHZPC. The results revealed that the optimal pH for dye removal in both single and mixed dye systems was found to be 9.0. The equilibrium time increased from 5 to 20 min when the system was changed from single to binary, and then further increased to 30 min when the system was changed to ternary. The equilibrium data for single-dye systems exhibited a good fit with the Langmuir isotherm model (R2 > 0.98, SEE <3.52 mg g−1), whereas for binary and ternary dye mixtures, the extended Langmuir model provided an accurate representation of the experimental data (R2 > 0.99, SEE <1.33 mg g−1). Among the single, binary, and ternary systems, the highest adsorption capacities were observed for MB, MB in the (MB + MG) binary system, and MB in the (MB + CV + MG) ternary system. The respective adsorption capacities were recorded as 79.55 mg g−1, 61.91 mg g−1, and 43.59 mg g−1. The adsorption of dyes onto the SNCs was inherently spontaneous and endothermic, and adhered to the pseudo-second-order kinetic model in single dye systems as well as mixed dye systems. It can be concluded that the SNCs are capable of being utilized for five consecutive cycles in the adsorption-desorption process for single dye systems and three consecutive cycles for mixed dye systems. This suggests that the SNCs have potential as a sustainable and efficient option for dye removal in mixture systems.

Graphene oxide-polydopamine loaded uniform fibrous membranes via robust multi-channel microfluidic-electrospinning method

The rapid development of modern industries has caused serious water pollution such as dyes wastewater, which brings environmental problems and threatens human health. Thus, methods allowing efficient dyes removal from wastewater are substantially desirable. In this work, we fabricated graphene oxide-polydopamine (GO-PDA) by microfluidics, which enables rapid synthesis of products with excellent uniformity due to the precise control of reaction conditions. In addition, the GO-PDA/ thermoplastic polyurethane (GO-PDA/TPU) composite fibrous membrane was prepared in a high-efficiency manner by microfluidic electrospinning with a four-channel chip. Interestingly, GO-PDA not only improves the mechanical strength and hydrophilicity of the composite fibrous membrane, but also endows the membrane with efficient dye adsorption and separation capacity both for single and mixed dyes. It has been proved that the GO-PDA/TPU composite fibrous membrane exhibits selectivity towards cationic dyes, where the removal efficiency is up to 99 wt%. Moreover, the fibrous membrane could be utilized in a continuous and cyclic manner, which still maintains a high adsorption rate (>95 wt%) after 5 recycling, illustrating outstanding durability and reusability. This work proposes an efficient GO-PDA/TPU composite fibrous membrane towards selective adsorption of cationic dyes, which is of great significance in wastewater purification.

A facile and green synthesis of corn cob-based graphene oxide and its modification with corn cob-K2CO3 for efficient removal of methylene blue dye: Adsorption mechanism, isotherm, and kinetic studies

In recent years, the treatment of synthetic dyes has become an environmental concern. In this study, a single step calcination process was used to develop the inventive, simple, and inexpensive adsorbent CC-GO/CC-K2CO3 composite. The composite was employed for the treatment of methylene blue (MB), a cationic dye. Several characterization methods including powder XRD, FTIR, XPS, BET, FESEM, EDX, Raman, and HRTEM techniques were utilized for the analysis of the composite. The surface area and mean pore diameter of CC-GO/CC-K2CO3 were 32.651 m2 g−1 and 3.71 nm, respectively. The adsorption experiment showed that optimal parameters for the removal of MB dye are at an adsorbent dose of 60 mg, initial dye concentration of 80 mg/L, contact time of 150 min, and pH value of 12 at room temperature. Under optimized conditions, CC-GO evidences a removal efficiency of 70.34 ± 1.36 % while after incorporation with CC-K2CO3 the removal capacity sharply increases up to 98.10 ± 0.4 %. Kinetic and isotherm models were used to analyze the removal rate constant and equilibrium adsorption capacity under various adsorption environments. The adsorption study was found to follow the models of pseudo-second order kinetic and Freundlich isotherm. The CC-GO/CC-K2CO3 composite has the maximum adsorption capacity (MAC) of 160.77 mg/g established by the Langmuir isotherm. The prepared composite has demonstrated the capacity to be recycled up to three times with a gradual decrease in its adsorption behavior, exhibiting removal efficiency of 61.66 ± 2.04 %.A cost estimation study of the composite was also performed to assess its cost effectiveness.

Comparison and Contrast of Calcite vs. Dolomite after Heat Treatment to Enhance Toluidine Blue Removal from Water

Significant increase in use of color dyes in modern society exerted a great pressure on environmental and water qualities. As such, studies for the removal of color dyes from water have been conducted extensively. In this study, common Earth materials dolomite and calcite were evaluated and contrasted for their removal of toluidine blue (TB), a cationic dye, before and after heat treatment. An increase by a factor of 3 in TB removal capacity from 3.5 to 10 mmol/kg was achieved after dolomite (Dol) was heated to 800 °C (designated as HDol). In contrast, the TB removal capacity increased by more than 100 times from 2 to 220 mmol/kg after calcite (Cal) was heated to 1000 °C (designated as HCal). For Dol and HDol, the TB removal increased as the solution’s pH increased but decreased with increases in the solution’s ionic strength. For Cal and HCal, the influence of the equilibrium solution’s pH and ionic strength on TB removal was negligible. The free energy of TB sorption on Dol, HDol, and Cal were −7 to −15 kJ/mol. The results suggested different removal mechanism for TB by Dol vs. Cal. X-ray diffraction data for Dol showed a slight increase in calcite content after heat treatment. For Cal, CaO was produced after heating, which converted back to calcite after 24 h of mixing with TB solutions. The significant TB removal by HCal could be attributed to its reaction with CaO. Thus, the best solution is to use freshly treated Cal for the removal of TB from solution.

Eco-friendly fabrication of ZnO-TiO2-rGO nanocomposite for efficient adsorption-assisted organic dyes elimination

The growing interest in combining the photocatalytic properties of semiconductors like ZnO and TiO2 with the superior electron conduction capabilities of graphene has resulted in the successful synthesis of in-situ reduced graphene oxide (rGO) supported ZnO-TiO2 nanostructures through a simple microwave-assisted synthesis method. X-ray Diffraction Spectroscopy (XRD), Field Emission Scanning Electron Microscope (FESEM), UV–visible spectroscopy (UV–vis), and Fourier Transform Infrared Spectroscopy (FTIR) were employed to characterize structural, morphological and optical properties as well as surface functional groups of the synthesized products. The XRD measurements of our synthesized samples confirm both structural crystallinity and phase purity, while the FTIR analysis verifies the complete reduction of graphene oxide (GO) to reduced graphene oxide (rGO). The synthesized ternary nanocomposite ZnO-TiO2-rGO exhibited a remarkable 100 % adsorption-assisted removal efficiency for 20 mg/L methylene blue (MB) dye under ultraviolet light illumination within 120 min, along with a 56 % dye adsorption removal efficiency in the same time interval. In comparison, pure ZnO showed 0 % adsorption and only 31 % photocatalytic efficiency at the similar condition. Remarkably, the ZnO-TiO2-rGO nanocomposite exhibited exceptional photocatalytic activity mediated by adsorption, achieving complete degradation of MB dye within 5 min under sunlight irradiation. The photocatalytic efficiency and dye adsorption capacity were found to be significantly lower for the anionic dye methyl orange (MO) compared to the cationic MB dye. The study thoroughly investigated the influence of catalyst dose and initial dye concentration on photodegradation. The proposed mechanism indicates that the extensive surface area and numerous active sites on the rGO promote adsorption, which is then followed by degradation through the metal oxides. Overall, the results unveil that the microwave-assisted synthesis of ZnO-TiO2-rGO nanocomposite is a promising and environmentally friendly approach for efficiently degrading dyes from contaminated wastewater using both UV light and natural sunlight irradiation.

Bio-sourced multifunctional adsorbent of chitosan and adipic acid activated-dragon fruit peels for organic dye removal from water: Eco-friendly management and valorization of biomass

Employing sustainable biomaterials obtained from waste biomass and biopolymers provides a very promising method for eliminating organic dyes from wastewater. This study presents a novel adsorbent of modified dragon fruit peels and chitosan, addressing wastewater treatment and environmental waste management. Precisely, a bio-sourced multifunctional (high level of functional groups) adsorbent (hereinafter, CHS/DFP-ADP) was developed from chitosan and adipic acid activated-dragon fruit (Hylocereus polyrhizus) peels. This biomaterial was applied to effectively adsorb organic pollutants (safranin O dye, SAF-O) from water. The adsorption variables, namely A: CHS/DFP-ADP dosage (0.02–0.08 g), B: pH (4–10), and C: duration (10–40 min), were modeled and optimized using the Box-Behnken Design (BBD). The results of the BBD model showed the optimum adsorption parameters for achieving the highest level of SAF-O removal (94.83 %) were as follows: CHS/DFP-ADP does = 0.049 g, the pH ∼ 10, and the contact duration = 40 min. The experimental results on the dye adsorption by CHS/DFP-ADP demonstrated conformity with the pseudo-first-order and Freundlich models. The biomaterial demonstrated a significant capability to adsorb SAF-O dye, with an adsorption capacity of 607.2 mg/g. The adsorption process of the cationic dye on the CHS/DFP-ADP involves several interactions, such as Yoshida H-bonding, electrostatic forces, n-π, and H-bonding. This work aligns with the principles of green chemistry and sustainable development, offering an innovative approach to tackle environmental concerns and promote the circular economy. The present effort meets several Sustainable Development Goals (SDGs), such as SDG 6 (Clean Water and Sanitation), SDG 12 (Responsible Consumption and Production), SDG 13 (Climate Action), and SDG 14 (Life Below Water).

Use of Brushite as Adsorbent for the Removal of Anionic and Cationic Dyes Present in Aqueous Solutions

Currently, water pollution caused by dyes is a serious problem since they are toxic and carcinogenic to living beings. To reduce the presence of these contaminants, natural adsorbents have been considered as they are easy to obtain, inexpensive, and have high removal efficiency. In this work, the adsorption process using natural brushite (nDCPD) was studied for the removal of phenol red (PR), achieving a removal rate of 99.15% and an adsorption capacity of 82.24 mg/g, and gentian violet (GV), achieving a removal rate of 97.03% and an adsorption capacity of 74.22 mg/g. Equilibrium adsorption occurs for both dyes in multiple layers on the surface. The adsorption process is spontaneous for both dyes. The kinetics of the adsorption process involve using a single active site on the surface for PR adsorption, while for GV, two active sites on the surface are required. Analysis via FTIR, EDS, and XRD revealed various mechanisms that intervene in the adsorption process of both dyes on the surface of nDCPD, such as electrostatic forces, functional groups, physisorption, and ion exchange.

Attraction behavior induces the aggregation and precipitation of organic dyes: Improving efficiency through co-treatment strategy

Organic dyes harm the environment through bioaccumulation, toxicity, water contamination, and persistence. Organic dyes are commonly charged species, while limited works reported the interaction behavior between the charges. In this study, seven typical organic dyes are selected to investigate the general rules of the aggregation-precipitation behaviors between cationic and anionic organic dyes at molecular scale. The maximum precipitation rates of organic dyes reached 96.0 % when the amount of positive charges of cationic dyes was stoichiometric to the negative charges of anionic dyes. The aggregation process is reversible in ethanol solvent and insensitive to temperature, indicating the aggregation behavior is a physical process. The aggregation behavior of cationic and anionic dyes in water and ethanol solvents was simulated at molecular scale. 94.9 % of water molecules dispersed out of the dye clusters within 20 picoseconds in the simulation, while only 0.8 % of ethanol dispersed under the same conditions. The inter-molecule van der Waals force of the ethanol-solvent system was higher than that of the water-solvent system, resulting in the failure of dyes aggregation in ethanol. This study proposed a concise strategy of mixing cationic and anionic dyes in charge balance to cause aggregation and co-precipitation of dyes to improve removal efficiency.