Equilibrium, kinetics and mechanism modeling and simulation of basic and acid dyes sorption onto jute fiber carbon: Eosin yellow, malachite green and crystal violet single component systems

The Use of Various Types of Waste Paper for the Removal of Anionic and Cationic Dyes from Aqueous Solutions

This study examined the possibility of using various types of waste paper-used newsprint (NP), used lightweight coated paper (LWC), used office paper (OP), and used corrugated cardboard (CC)-for the removal of anionic dyes, Acid Red 18 (AR18) and Acid Yellow 23 (AY23), and cationic dyes, Basic Violet 10 (BV10) and Basic Red 46 (BR46), from aqueous solutions. The scope of this research included the characterization of sorbents (FTIR, SEM, BET surface area, porosity, pHPZC, effectiveness of water coloration), determination of pH effect on the effectiveness of dye sorption, sorption kinetics (pseudo-first-order model, second-order model, intraparticular diffusion model), and the maximum sorption capacity (Langmuir models and Freundlich model) of the tested sorbents. The use of waste paper materials as sorbents was found to not pose any severe risk of aquatic environment contamination. AR18, AY23, and BV10 sorption intensities were the highest at pH 2, and that of RB46 at pH 6. The waste paper sorbents proved particularly effective in removing cationic dyes, like in the case of, e.g., NP, which had a sorption capacity that reached 38.87 mg/g and 90.82 mg/g towards BV10 and BR46, respectively, and were comparable with that of selected activated carbons (literature data).

Salsola Tetragona as a new low-cost adsorbent for water treatment: highly effective adsorption of crystal violet

Synthetic dyes are prevalent in aquatic environments, they have high toxicities, are non-degradable, and accumulate in the water. The removal of Crystal violet (CV) is carried out using batch experiments on the Salsola Tetragona (ST) plant as a novel adsorbent. The prepared adsorbent was analyzed by various methods (MEB, EDX, IRTF and PZC), to support its applicability as adsorbent. The adsorption study of CV is performed by optimizing the parameters affecting the adsorption process. The adsorption kinetics study is represented by pseudo-second-order (R2 = 0.999) and the adsorption process is limited by external mass transport. In addition, the isotherm results demonstrate that the Langmuir model interprets better the adsorption isotherm. The thermodynamic parameters suggest that the adsorption phenomena are spontaneous and exothermic. Furthermore, the adsorption reactions involved are of physisorption type, which facilitates the desorption of pollutants from the surface of the adsorbent. The results show that ST adsorbent effectively removes CV in an aqueous solution, which is demonstrated by the maximum amount adsorption of 246.7 mg.g-1 at optimum adsorption conditions: pH = 6, adsorbent dose of 0.5 g.L-1, initial CV concentration of 10 mg.L-1, and adsorption time of 30 min at 298 K. Finally, these results can be considered as a useful reference for wastewater treatment using ST.

Removal of doxorubicin hydrochloride and crystal violet from aqueous solutions using spray-dried niobium oxide coated with chitosan-activated carbon: Experimental and DFT calculations

Spray-dried niobium oxide coated with chitosan-activated carbon (NIC) was synthesized and used to remove doxorubicin hydrochloride and crystal violet from aqueous solutions under different parameters such as solution pH (2, 4, 6, and 8), contact time (1 to 9 h), initial concentration (20 to 200 mg L-1), and competing ions (0.1 M of CaCl2 and NaCl). The addition of 5 % chitosan-activated carbon to the matrix of niobium oxide slightly increased the specific surface area from 26 to 30 m2 g-1, with the introduction of a carboxylic functional group. This led to an increase in the amount of adsorbed doxorubicin hydrochloride (DOH) from 30 to 44 mg g-1 and that of crystal violet (CV) from 15 to 32 mg g-1 from the initial respective 100 mg L-1 at pH 8. The data from the concentration study fitted into Liu isotherm having adsorption capacity of 128 and 57 mg g-1 for DOH and CV respectively, while pseudo first and second order are more suitable for adsorption kinetics. The additional functional groups on the IR spectrum of NIC after the adsorption of DOH and CV confirmed the interaction between NIC and the adsorbates' molecules. The mechanism of adsorption was supported by DFT calculations.

Polypyrrole-decorated bentonite magnetic nanocomposite: A green approach for adsorption of anionic methyl orange and cationic crystal violet dyes from contaminated water

In the presented study, a novel polypyrrole-decorated bentonite magnetic nanocomposite (MBnPPy) was synthesized for efficient removal of both anionic methyl orange (MO) and cationic crystal violet (CV) dyes from contaminated water. The synthesis of this novel adsorbent involved a two-step process: the magnetization of bentonite followed by its modification through in-situ chemical polymerization. The adsorbent was characterized by SEM/EDX, TEM/SAED, BET, TGA/DTA-DTG, FTIR, VSM, and XRD studies. The investigation of the adsorption properties of MBnPPy was focused on optimizing various parameters, such as dye concentration, medium pH, dosage, contact time, and temperature. The optimal conditions were established as follows: dye concentration of Co (CV/MO) at 100 mg/L, MBnPPy dosage at 2.0 g/L, equilibrium time set at 105 min for MO and 120 min for CV, medium pH adjusted to 5.0 for MO dye and 8.0 for CV dye, and a constant temperature of 303.15 K. The different kinetic and isotherm models were applied to fit the experimental results, and it was observed that the Pseudo-2nd-order kinetics and Langmuir adsorption isotherm were the best-fitted models. The maximal monolayer adsorption capacities of the adsorbent were found to be 78.74 mg/g and 98.04 mg/g (at 303.15 K) for CV and MO, respectively. The adsorption process for both dyes was exothermic and spontaneous. Furthermore, a reasonably good regeneration ability of MBnPPy (>83.45%/82.65% for CV/MO) was noted for up to 5 adsorption-desorption cycles with little degradation. The advantages of facile synthesis, cost-effectiveness, non-toxicity, strong adsorption capabilities for both anionic and cationic dyes, and easy separability with an external magnetic field make MBnPPy novel.

Advancements in textile dye removal: a critical review of layered double hydroxides and clay minerals as efficient adsorbents

The textile industry is responsible for producing large volumes of wastewater that contain a wide variety of dye compounds. This poses a significant environmental hazard and risks harming both ecosystems and living organisms. This review study explores the advancements in adsorption research for dye removal, with a particular emphasis on the development of various adsorbents. The article provides detailed insights into the toxicity and classification of dyes, different treatment techniques, and the characteristics of numerous adsorbents, with special attention to layered double hydroxides (LDH) and clay minerals. A comprehensive list of adsorbents, encompassing natural materials, agricultural by-products, industrial waste, and activated carbon, is discussed for effective removal of different dyes. Furthermore, the review extensively examines the influence of various adsorption variables, such as pH, initial dye concentration, adsorbent dosage, temperature, contact time, ionic strength, and pore volume of the adsorbent. Additionally, the application of response surface methodology for optimizing adsorption variables is elucidated. Commonly, electrostatic attraction, π-π interactions, n-π interactions, van der Waals forces, H-bonding, and pore diffusion play a major role in adsorption mechanism. The review also found that LDH can eliminate a wide range of dyes from wastewater, achieving excellent uptake capacities often exceeding 500 mg/g, with a removal efficiency of 99%. The Langmuir isotherm and pseudo-second-order kinetic equations gave the best fit to most of the adsorption data. Overall, this review serves as a valuable resource for researchers and practitioners seeking sustainable solutions to address the environmental challenges posed by textile dye contamination.

Preparation and application of the thermo-/pH-/ ion-sensitive semi-IPN hydrogel based on chitosan

Chitosan based hydrogels with multiple stimulus responses have broad application prospects in many fields. Considering the advantages of semi interpenetrating network (IPN) technology and the special temperature and ion responsiveness of polymers containing zwitterionic groups, a semi-IPN hydrogel was prepared through in situ free radical polymerization of N,N-dimethyl acrylamide and [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl) ammonium hydroxide with polyethylene glycol dimethacrylate as a crosslinker and carboxymethyl chitosan as filler. The gel mass fraction and swelling ratio were measured, and the preparation conditions were optimized. The result indicated that the hydrogel possessed a unique thermo-/pH-/ ion-sensitive behavior. The swelling ratio increased with the increase of temperature and ion concentration, and showed a decreasing trend with the increase in pH. In addition, the hydrogel was stable when the stimuli changed. Adsorption behavior of the hydrogel to Eosin Y (EY) was systematically investigated. The adsorption process can be described well by the pseudo-second-order kinetic model and Langmuir isotherm model, indicating that it was a chemical adsorption. The experiments indicated that the hydrogel exhibited good antifouling and reusability features. Therefore, the semi-IPN hydrogel with antifouling properties and thermo-/pH-/ion-sensitivity can be easily manufactured is expected to find applications in water treatment fields.

Phytoremediative adsorption methodologies to decontaminate water from dyes and organic pollutants

Persistent organic pollutants and dyes cause major problems during ecofriendly wastewater treatment. To overcome this huge problem, several techniques have been considered and in practice for the safe disposal of organic pollutants in recent years; some of them are discussed and compared herein. This review focuses on new trends for wastewater treatment and compares them with certain other techniques alongside their pros and cons; adsorption is considered the safest among them. Adsorbents derived from agri-wastes have good capacity for the removal of these contaminants owing to their great sorption capacity, high reusability, easy operation, etc. Sometimes they need some modifications for the removal of dyes, which are also discussed in this review. This capacity of adsorbents to chelate dye molecules can be affected by factors, such as pH, the concentration of dyes and adsorbents, and temperature of the system. pH has direct influence on the ionization potential and charge on the outer surface of adsorbents. The findings on isotherms, kinetics, and desorption of plant waste-based biomaterials that are safe for the ecosystem and user friendly and are used for hazardous contaminant removal from water are summarized in this review. Finally, conclusions and future perspectives are presented, and some other materials, such as CNTs and MOFs, are also discussed as efficient adsorbents for eliminating dyes from wastewater. Finally, it is predicted that the adsorption of dyes is a more feasible solution for this dye pollution problem.

Bioremediation of malachite green dye using sodium alginate, Sargassum latifolium extract, and their silver nanoparticles

INTRODUCTION

The textile, paper, rubber, plastic, leather, cosmetics, pharmaceutical, and food sectors extensively use malachite green (MG). In spite of this, it has mutagenic, carcinogenic, teratogenic, and, in some circumstances causes chronic respiratory disease.

OBJECTIVES

In this work, we used sodium alginate, Sargassum latifolium aqueous extract, and their silver nanoparticles to test their potential as inexpensive adsorbent agents to remove malachite green dye from aqueous solutions.

METHODS

The removal rate of MG was determined using a series of bioadsorption experiments. Besides, the effect of different factors on bioadsorption, such as pH, adsorbent dose, contact time (min), and different concentrations of MG dye was investigated.

RESULTS

The removal efficiency of MG dye by alginate nanoparticles, alginate, Sargassum latifolium aqueous extract, and S. latifolium aqueous extract nanoparticles was 91, 82, 84, and 68 respectively. The optimal conditions for bioadsorption of malachite green dye were pH 7, a contact time of 180 min, and an adsorbent dose of 0.02 g. The adsorption isotherm was fitted to Langmuir and Freundlich isotherm. Also, UV and FT-IR before and after the bioadsorption of MG were performed to confirm the bioadsorption process.

CONCLUSION

Our results indicated that alginate nanoparticles were the most effective bioadsorbent agent.

Thermoplastic starch (TPS)-based composite films for wastewater treatment: synthesis and fundamental characterization

Modification of starch is a potential basic research aiming to improve its water barrier properties. The general purpose of this study is to manufacture cross-linked iodinated starch citrate (ISC) with a degree of substitution (DS) ≈ 0.1 by modifying native corn starch with citric acid in the presence of iodine as an oxidizing agent. Thermoplastic starch (TPS) was generated with urea as a plasticizer and blended with various concentrations of ISC of (2, 4, 6%) (wt/wt) to obtain (UTPS/ISC₂, UTPS/ISC₄, and UTPS/ISC₆). Nanocomposite film was formed from UTPS/ISC₂ in presence of stabilized iodinated cellulose nanocrystals UTPS/ISC₂/SICNCs via gelatinization at a temperature of 80ºC. Water solubility and water vapor release were studied amongst the water barrier features. The fabricated starch-based composite films were evaluated utilizing Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electronic Microscope analysis (SEM), surface area, and tensile measurements. The adsorption of crystal violet (CV) dye onto produced samples was examined in an aqueous solution. The findings revealed that the UTPS/ISC₂/ISCNCs has 83% crystal violet elimination effectiveness. Moreover, the adsorption isotherms were assessed and figured out to vary in the order of Langmuir > Temkin > Freundlich > Dubinin-Radushkevich.

Biosorption of Triphenyl Methane Dyes (Malachite Green and Crystal Violet) from Aqueous Media by Alfa (Stipa tenacissima L.) Leaf Powder

This study includes the characterization and exploitation of an abundant agricultural waste in Algeria, Alfa (Stipa tenacissima L.) leaf powder (ALP) as a biosorbent for the removal of hazardous triphenylmethane dyes, malachite green (basic green 4) and crystal violet (basic violet 3), from aqueous media under various operating conditions in batch mode. The effect of experimental parameters such as initial dye concentration (10-40 mg/L), contact time (0-300 min), biosorbent dose (2.5-5.5 g/L), initial pH (2-8), temperature (298-328 K), and ionic strength on dye sorption was investigated. The results of both dyes show that the increase in initial concentration, contact time, temperature, and initial pH of solution leads to an increase in biosorbed quantity, unlike the effect of ionic strength. The biosorption kinetics for triphenylmethane dyes on ALP was analyzed by pseudo-first-order, pseudo-second-order, Elovich, and intraparticle diffusion models proposed by the Weber-Morris equation. Equilibrium sorption data were analyzed by six isotherms, namely the Langmuir, Freundlich, Harkins-Jura, Flory-Huggins, Elovich, and Kiselev isotherms. The thermodynamic parameters were evaluated for both dyes. The thermodynamic results suggest that both dyes' biosorption is a typical physical process, spontaneous and endothermic in nature.

Ficus Benjamin's leaf, a native sorbent for the exclusion of Methyl violet 10B from aquatic media

Due to the use of non-recyclable materials and the high costs of the technologies, removal of dyes from wastewater is becoming more and more pricey. This paper presents the capacity of Ficus Benjamina (FB) leaf powder to eradicate methyl violet dye 10 B (MV) in an aqueous fluid. The surface characteristics and presence of various functional groups on the surface of sorbent were revealed by SEM and FTIR studies. Diverse constraints on the elimination of methyl violet 10 B in an aqueous environment were also studied, including starting dye concentration, temperature, and contact duration. The Elovich & liquid film diffusion models, along with Lagergren first-order, pseudo-second-order, Bangham, and modified Freundlich modeling operated to assess kinetics. Experiments confirmed the pseudo-second-order concept. To investigate tentative data, multiple linear Langmuir, Freundlich, Temkin, as well as two parameters nonlinear isotherm models were applied, with findings indicating that sorption data were like both linear and non-linear isotherms. Sorption data were found to be in excellent agreement with the Freundlich isotherm with R² value (0.99). The sorption capacity of the sorbent was computed i.e. 312.2 mg/g. Thermodynamic characteristics were also computed. It was concluded that the sorption of methyl violet 10 B sorption on FB leaf powder is exothermic. Hence, it is a potentially cost-effective bio sorbent for exclusion of dye from wastewater.

Statistically optimized sequential hydrothermal route for FeTiO3 surface modification: evaluation of hazardous cationic dyes adsorptive removal

In the present study, the performance of facile hybrid sequential chemical treatments of titanomagnetite concentrate (TC), alkaline leaching, and sodium dodecyl sulfate (SDS) modification has been evaluated for the removal of crystal violet (CV), malachite green (MG), and methylene blue (MB) cationic dyes. The physical and chemical properties of samples were characterized using scanning electron microscopy (SEM), energy dispersive X-ray (EDX), N₂ adsorption-desorption, X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), and Fourier transform infrared spectroscopy (FTIR) analyses. Moreover, dye removal in the batch system was investigated by evaluating adsorbent dosage, contact time, initial dye concentration, pH of the solution, temperature, electrolyte concentration, adsorption isotherm, kinetic, and thermodynamic. The results showed that the maximum adsorption capacity was obtained at SDS concentration of 6 mM, NaOH concentration of 9 M, the temperature of 160 °C, solid/liquid ratio of 4 g/100 mL, and the process duration of 24 h. In the alkaline leaching process, forming the Na₂TiO₃ phase with sharp and high energy points can be improved the adsorption properties. Accordingly, the adsorption capacity and removal efficiency attained 19.84, 18.64, and 19.66 mg/g and 99.21, 93.24, and 98.31% for CV, MG, and MB, respectively. Furthermore, the dye removal followed pseudo-second-order (R² = 0.9990) and Freundlich (R² = 0.9970) models. The evaluation of thermodynamic parameters indicated the endothermic (∆H° = 110.91 J/mol) and spontaneous nature (ΔG˚ < 0) of the adsorption process. This study concluded that the modified TC had a potential ability for application in textile wastewater treatment.

The Use of Chitin from the Molts of Mealworm (Tenebrio molitor) for the Removal of Anionic and Cationic Dyes from Aqueous Solutions

The possibility of using chitin from the molts of an insect-ealworm (Tenebrio molitor) to remove anionic (RB5, RY84) and cationic dyes (BV10, BR46) from aqueous solutions was investigated. The scope of the research included, among others: Characteristics of chitin from mealworms (FTIR, SEM, pH_PZC), the effect of pH on sorption efficiency, sorption kinetics (pseudo-first, pseudo-second order, intramolecular diffusion models) and the determination of the maximum sorption capacity (Langmuir and Freundlich models). The sorption efficiency of anionic dyes on chitin from mealworm was the highest at pH 2-3, and for cationic dyes at pH 6. The equilibrium time of sorption of anionic dyes was 240-300 min and for cationic dyes it was 180-240 min. The experimental data on dye sorption kinetics was best described by the pseudo-second order model. The maximum sorption capacity of chitin from the mealworm for the anionic dyes RB5 and RY84 was 121.15 mg/g and 138.55 mg/g, respectively, and was higher than with some carbon-based materials (literature data). In the case of cationic dyes, the sorption capacity of the tested chitin was lower and reached 3.22 mg/g and 59.56 mg/g for BV10 and BR46, respectively.

Synthesis, characterization, antimicrobial and photocatalytic properties of nano-silver-doped flax fibers

In the present study, the nano-silver-doped flax fibers (NAgDFF) are prepared in two steps. In the first step, oxidation of the flax fibers is performed by potassium periodate to form dialdehyde cellulose (DAC) and the second step is the reduction of silver ions by DAC. A series of characterization techniques of the photocatalyst NAgDFF was carried out using scanning electron microscopy, Fourier transform infrared spectroscopy, N2 adsorption isotherm, thermogravimetric analysis and energy-dispersive X-ray spectroscopy. The dye degradation potential of NAgDFF for methylene blue (MB), crystal violet (CV) and brilliant green (BG) (individually or mixture) was investigated using batch and column tests. The degradation efficiency was studied under optimized conditions such as pH (5.0), dye initial concentrations (100 ppm for MB and BG, and 150 ppm for CV), contact time (3.0 h), photocatalyst NAgDFF dose (0.08 g) and temperature (25° C). The maximum degradation efficiency of NAgDFF for MB, CV and BG is 64.75, 94.98 and 63.87 (mg/g), respectively. The kinetic studies show that the experimental data match well with the pseudo-second-order kinetic model. Furthermore, equilibrium isotherm data were analyzed according to Langmuir, Freundlich and Dubinin–Radushkevich equations. The thermodynamic parameters for the adsorption processes of cationic dyes on the NAgDFF fibers were also calculated; the negative value of ΔG° indicated the spontaneous nature of sorption. NAgDFF fibers were successfully applied for photodegradation of the investigated cationic dyes from different samples. The study was extended to investigate the biological activity of newly synthesized NAgDFF against various microorganisms.

Activated Carbon/ZnFe2O4 Nanocomposite Adsorbent for Efficient Removal of Crystal Violet Cationic Dye from Aqueous Solutions

The aim of this study was to investigate the potential advantage of ZnFe₂O₄-incorporated activated carbon (ZFAC), fabricated via a simple wet homogenization, on the removal of cationic dye crystal violet (CV) from its aqueous solutions. The as-prepared ZFAC nanocomposite was characterized using Fourier transform infrared (FTIR), X-ray diffraction (XRD), nitrogen adsorption, scanning electron microscope (SEM), thermogravimetric analysis (TGA), and ultraviolet-visible (UV-Vis). Batch adsorption operating conditions such as the pH (3-11), CV concentration (25-200 ppm), ZFAC dose (10-50 mg), temperature (23-45 °C), and contact time were evaluated. The results indicate pH-dependent uptake (optimum at pH 7.2) increased with temperature and CV concentration increase and decreased as adsorbent dose increased. Modeling of experimental data revealed better fit to the Langmuir than Freundlich and Temkin isotherms, with maximum monolayer capacities (Q_m) of 208.29, 234.03, and 246.19 mg/g at 23, 35, and 45 °C, respectively. Kinetic studies suggest pseudo-second order; however, the intra-particle diffusion model indicates a rate-limiting step controlled by film diffusion mechanism. Based on the thermodynamic parameters, the sorption is spontaneous (-ΔG°), endothermic (+ΔH°), and random process (+ΔS°), and their values support the physical adsorption mechanism. In addition to the ease of preparation, the results confirm the potential of ZFAC as a purifier for dye removal from polluted water.

Adsorption of Crystal Violet Dye from Aqueous Solution using Industrial Pepper Seed Spent: Equilibrium, Thermodynamic, and Kinetic Studies

The economic viability of adsorbing crystal violet (CV) using pepper seed spent (PSS) as a biosorbent in an aqueous solution has been studied. A parametrical investigation was conducted considering parameters like initial concentration of dye, time of contact, pH value, and temperature variation. The analysis of experimental data obtained was carried out by evaluating with the isotherms of Freundlich, Sips, Tempkin, Jovanovic, Brouers–Sotolongo, Toth, Vieth–Sladek, Radke–Prausnitz, Langmuir, and Redlich–Peterson. The adsorption kinetics were studied by implementing the Dumwald-Wagner, Weber-Morris, pseudo-first-order, pseudo-second-order, film diffusion, and Avrami models. The experimental value of adsorption capacity ( $Q_m=129.4\text{mg}{\text{g}}^{-1}$ ) was observed to be quite close to the Jovanovic isotherm adsorption capacity ( $Q_m=82.24\text{mg}{\text{g}}^{-1}$ ) at ( $R^2$ ), coefficient of correlation of 0.945. The data validation was found to conform to that of pseudo-second-order and Avrami kinetic models. The adsorption process was specified as a spontaneous and endothermic process owing to the thermodynamic parametrical values of $\Delta G^0$ , $\Delta H^0$ , and $\Delta S^0$ . The value of $\Delta H^0$ is an indicator of the process’s physical nature. The adsorption of CV to the PSS was authenticated from infrared spectroscopy and scanning electron microscopy images. The interactions of the CV-PSS system have been discussed, and the observations noted suggest PSS as a feasible adsorbent to extract CV from an aqueous solution.

Recent Advances in MOF-Based Adsorbents for Dye Removal from the Aquatic Environment

The adsorptive removal of dyes from industrial wastewater using commercially available adsorbents is not significantly efficient. Metal–organic frameworks (MOFs) offer outstanding properties which can boost the separation performance over current commercial adsorbents and hence, these materials represent a milestone in improving treatment methods for dye removal from water. Accordingly, in this paper, the recent studies in the modification of MOF structures in dye removal from the aquatic environment have been discussed. This study aims to elaborate on the synthetic strategies applied to improve the adsorption efficiency and to discuss the major adsorption mechanisms as well as the most influential parameters in the adsorptive removal of dyes using MOFs. More particularly, the advanced separation performance of MOF-based adsorbents will be comprehensively explained. The introduction of various functional groups and nanomaterials, such as amine functional groups, magnetic nanoparticles, and carbon-based materials such as graphene oxide and CNT, onto the MOFs can alter the removal efficiency of MOF-based adsorbents through enhancing the water stability, dispersion in water, interactions between the MOF structure and the contaminant, and the adsorption capacity. Finally, we summarize the challenges experienced by MOF-based materials for dye removal from water and propose future research outlooks to be considered.

Green synthesis of zinc oxide nanoparticles loaded on activated carbon prepared from walnut peel extract for the removal of Eosin Y and Erythrosine B dyes from aqueous solution: experimental approaches, kinetics models, and thermodynamic studies

Water contamination due to release of dye containing effluents is one of the environmental problems of serious concern today. The present study investigate the green synthesis of zinc oxide nanoparticles (ZnO-NPs) doped on activated carbon (AC) prepared from walnut peel extract and to estimate its efficiency in the removal of Eosin Y (Eo-Y) and Erythrosine B (Er-B) from its aqueous solution. The synthesized AC-ZnO was identified by field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and the Brunauer-Emmett-Teller. The influence of various parameters such as pH, dosage of AC-ZnO, contact time, and concentrations of Eo-Y and Er-B was also studied. The pH 3 was observed as the optimum pH while the equilibrium was noticed to reach in 30 min at dosage of 1 g/L and initial concentration 100 mg/L for Eo-Y and Er-B adsorption onto AC-ZnO. The maximum adsorption capacity of Eo-Y and Er-B onto AC-ZnO was found to be 163.9 and 144.92 mg/g (and removal efficiencies of 95.11 and 98.31 %), respectively. The process of Eo-Y and Er-B adsorption on AC-ZnO was observed to be depended on the pseudo-second-order kinetic model which indicates chemisorption processes. Langmuir adsorption isotherm model test described the removal of Eo-Y and Er-B on AC-ZnO. The thermodynamic data indicated that the adsorption was endothermic process. Also, the values, S_BET and V_TOTAL, for the AC-ZnO were equal to 725.65 m²/g and 0.6004 cm³/g, respectively. The results of this study exhibited that AC-ZnO was a very effective method that can be used for the removal of Eo-Y and Er-B from aqueous solutions.

Engineering of appropriate pore size combined with sulfonic functionalization in a Zr-MOF with reo topology for the ultra-high removal of cationic malachite green dye from an aqueous medium

A Zr-based metal–organic framework with reo topology, denoted as Reo-MOF-1, was fabricated through a solvothermal method capable of efficiently removing the cationic MG dye from an aqueous medium.

Integrated experimental and theoretical insights for Malachite Green Dye adsorption from wastewater using low cost adsorbent

Water pollution is one of the problems that threaten humanity, and to confront it with only experimental procedures is not enough. It is necessary to integrate both practical methods and theoretical calculations to achieve decontamination with the most accurate interpretation. Hence, discussing the experimental mechanism study of Malachite Green (MG) dye adsorption with the help of the application of density functional theory (DFT) calculations is the main goal of this article. The experimental results affirmed that the preparation of γ-Al₂O₃ by precipitation method using (NH₄)₂CO₃ improved the porosity, the surface capability, and the adsorbent capacities (q_max = 210 mg/g) at optimum condition compared with the previous studies. Kinetic and equilibrium studies showed that the adsorption follows the pseudo-second-order model and Freundlich isotherm model, respectively. Also, the calculated and observed thermodynamic parameters exerted positive values of ΔH° and ΔS°, which translates into an endothermic process with increasing disorder of the system. Theoretical calculations at DFT- B3LYP/6-31G (d,P) level of theory were calculated to show the selectivity of using the cationic form of MG in the experimental measurements to find the interaction mechanism. The electronic structure and intramolecular charge transfer of MG, its cationic form and the complex of MG-Al were investigated theoretically at the B3LYP/6-31 G (d,p) level of theory. The equilibrium geometries of MG, its cationic form and the complex of MG-Al were determined, and it was found that these geometries are non-planar. The E_HOMO and E_LUMO energies can be used to calculate the global properties; chemical hardness (η), softness (S) and electronegativity (χ). The calculated non-linear optical parameters (NLO) of the studied compounds, the electronic dipole moment (μ), first-order hyperpolarizability (β), the hyper-Rayleigh scattering (β_HRS) and the depolarization ratio (DR), showed promising optical properties. Finally, the computational and the experimental results indicated that the adsorption efficiency of MG from wastewater was directly associated with the dye electrophilicity power.

Sodium Docusate Surface-Modified Dispersible and Powder Zinc Peroxide Formulation: An Adsorbent for the Effective and Fast Removal of Crystal Violet Dye, an Emerging Wastewater Contaminant

Crystal violet (CV) dye is one of the most toxic dyes majorly generated by textile industries. It may cause health issues if enters human beings. A lot of research has been reported for the removal of CV dye from wastewater; however, most of them are time-consuming and hardly remove more than 95% of the CV dye. In the last few years, we have tested several materials, and most of them have exhibited very low efficacy toward adsorption of CV including zinc peroxide (ZnO2). To enhance adsorption efficacy, dispersibility, and stability, the surfaces of several reported materials were modified using different wetting agents and nonionic surfactants. Interestingly, ZnO2, which was earlier very less effective after surface modification by sodium salt of dioctyl sulfosuccinate, efficiently adsorbed >99.5% of CV from contaminated water within 5 min of contact time at pH ∼10. The adsorption capacity obtained for the sodium docusate surface-modified zinc peroxide (ZnSD) adsorbent was found to be 123 mg/g, which is much better than the other reported for CV removal. Different physiochemical experiment parameters like pH, contact time, initial dye concentration, adsorbent dosages, and temperature were optimum to achieve maximum adsorption of the CV dye. The adsorption rate and adsorption mechanism studies show that the adsorption of CV follows pseudo-second-order kinematics and the Freundlich isotherm model. The adsorption results are consistent, and even treated water can be reutilized for various applications.

The use of spent coffee grounds and spent green tea leaves for the removal of cationic dyes from aqueous solutions

This study aimed to examine sorption effectiveness of cationic dyes: Basic Red 46 (BR46) and Basic Violet 10 (BV10) onto spent coffee ground (CG) and spent green tea leaves (GTL). The scope of the study included, i.a.: sorbent FTIR spectra analysis, determination of pH effect on dye sorption effectiveness, analysis of dye sorption kinetics, and determination of maximal sorption capacity of the sorbents. The effectiveness of BR46 sorption on the sorbents tested was the highest at pH 6 and that of BV10 at pH 3. Both sorbents caused changes in solution pH during the sorption process, due to the system tending to reach the pH value approximating the pH_ZPC (pH_PZC = 7.55 for CG and pH_PZC = 7.05 for GTL). The time needed to reach BR46 and BV10 sorption equilibrium onto CG and GTL ranged from 180 to 240 min. The intramolecular diffusion model demonstrated that the sorption of cationic dyes onto CG and GTL proceeded in three phases differing in the intensity and duration. The maximal sorption capacity of CG reached 179.4 mg/g for BR46 and 59.3 mg/g for BV10. The sorption capacity of GTL was lower and reached 58.0 mg/g for BR46 and 26.7 mg/g for BV10.

Adsorptive Performance of Polypyrrole-Based KOH-Activated Carbon for the Cationic Dye Crystal Violet: Kinetic and Equilibrium Studies

The aim of this work was to investigate the adsorptive performance of the polypyrrole-based KOH-activated carbon (PACK) in the removal of the basic dye crystal violet (CV) using a batch adsorption system. The equilibrium data, obtained at different initial CV concentrations ( $C_0=50–500\text{mg}/\text{L}$ ) and temperatures (25–45°C), were interpreted using the Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherms, with the Langmuir model providing a better fit ( $R^2\ge 0.9997$ ) and a maximum adsorption capacity of 497.51 mg/g at 45°C. Under the examined conditions, the values of the thermodynamic parameters free energy, enthalpy, and entropy indicate a spontaneous, endothermic, and physisorption adsorption process. The kinetic data of the adsorption process were very well described by a pseudo-second-order model ( $R^2\ge 0.9996$ ). However, surface diffusion seems to be the main rate-controlling step. Thus, we concluded that PACK shows commercial potential for the removal of cationic dyes such as CV from industrial effluent.

Effective Removal of Crystal Violet Dye Using Neoteric Magnetic Nanostructures Based on Functionalized Poly(Benzofuran-co-Arylacetic Acid): Investigation of the Adsorption Behaviour and Reusability

Synthetic dyes represent a significant class of contaminants released in the environment. Crystal violet is a triarylmethane dye used in several fields such as printing inks, the textile or paper industries, as well as in cell histology. Coating magnetic nanoparticles with functionalized polymers has been proved to improve their efficiency, offering unique properties for applications in wastewater treatment. The current paper focuses on preparing and characterising magnetic core-shell nanoparticles coated with poly(benzofuran-co-arylacetic acid) functionalized with folic acid as an organic shell. The new polymer-based magnetic nanostructures were applied for crystal violet extraction from aqueous solutions. The nanostructures were structurally and morphologically investigated by Fourier-transform infrared (FTIR) spectroscopy and transmission electron microscopy (TEM). While thermal and magnetic properties of the magnetic nanostructures were determined by thermogravimetric analysis (TGA) and magnetization measurements (VSM). At the same time, crystal violet concentrations were determined by UV-VIS spectroscopy. The influence of initial dye concentration and contact time on the removal efficiency has been studied to achieve the optimum adsorption conditions. The dye adsorbent neoteric magnetic nanostructure was easily desorbed and reused, the adsorption capacity decreasing from 100% to 97.63% in the first five cycles, reaching a minimum of 88.74% after the 10th recycling step.

Interactions of extracellular DNA with aromatized biochar and protection against degradation by DNase I

With increasing environmental application, biochar (BC) will inevitably interact with and impact environmental behaviors of widely distributed extracellular DNA (eDNA), which however still remains to be studied. Herein, the adsorption/desorption and the degradation by nucleases of eDNA on three aromatized BCs pyrolyzed at 700 °C were firstly investigated. The results show that the eDNA was irreversibly adsorbed by aromatized BCs and the pseudo-second-order and Freundlich models accurately described the adsorption process. Increasing solution ionic strength or decreasing pH below 5.0 significantly increased the eDNA adsorption on BCs. However, increasing pH from 5.0 to 10.0 faintly decreased eDNA adsorption. Electrostatic interaction, Ca ion bridge interaction, and π-π interaction between eDNA and BC could dominate the eDNA adsorption, while ligand exchange and hydrophobic interactions were minor contributors. The presence of BCs provided a certain protection to eDNA against degradation by DNase I. BC-bound eDNA could be partly degraded by nuclease, while BC-bound nuclease completely lost its degradability. These findings are of fundamental significance for the potential application of biochar in eDNA dissemination management and evaluating the environmental fate of eDNA.

Chitin-psyllium based aerogel for the efficient removal of crystal violet from aqueous solutions

A new alternative aerogel was prepared from low-cost chitin and psyllium biopolymers to adsorb crystal violet (CV) dye from liquid media and possibly treat effluents containing other dyes. The aerogel was characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM), which demonstrated that aerogel has a typical structure of amorphous materials and presented a randomly interconnected porous structure that resembles an open pore network. 2.5 g L^-1 of aerogel was able to remove 86.00% of CV from solutions, and the natural pH of the CV solution was considered the more adequate for adsorption. The pseudo-second-order (PSO) model satisfactorily described the adsorption kinetics, and the Freundlich model was suitable to represent the adsorption equilibrium. The maximum experimental capacity achieved was 227.11 mg g^-1, which indicates that aerogel is very efficient and competitive with several adsorbents. Tests using a simulated effluent showed that aerogel has excellent potential to treat real colored effluents.

Application of Cordia trichotoma sawdust as an effective biosorbent for removal of crystal violet from aqueous solution in batch system and fixed-bed column

In this work, for the first time, Cordia trichotoma sawdust, a residue derived from noble wood processing, was applied as an alternative biosorbent for the removal of crystal violet by discontinuous and continuous biosorption processes. The optimum conditions for biosorption of crystal violet were 7.5 pH and a biosorbent dosage of 0.8 g L^-1. The biosorption kinetics showed that the equilibrium was reached at 120 min, achieving a maximum biosorption capacity of 107 mg g^-1 for initial dye concentration of 200 mg L^-1. The Elovich model was the proper model for representing the biosorption kinetics. The isotherm assays showed that the rise of temperature causes an increase in the biosorption capacity of the crystal violet, with a maximum biosorption capacity of 129.77 mg g^-1 at 328 K. The Langmuir model was the most proper model for describing the behavior. The sign of ΔG⁰ indicates that the process was spontaneous and favorable, whereas the ΔH⁰ indicates an endothermic process. The treatment of the colored simulated effluent composed by dyes and salts resulted in 80% of color removal. The application of biosorbent in the fixed-bed system achieved a breakthrough time of 505 min, resulting in 83.35% of color removal. The Thomas and Yoon-Nelson models were able to describe the fixed-bed biosorption behavior. This collection of experimental evidence shows that the Cordia trichotoma sawdust can be applied for the removal of crystal violet and a mixture of other dyes that contain them.

Efficient removal of various coexisting organic pollutants in water based on β-cyclodextrin polymer modified flower-like Fe3O4 particles

HYPOTHESIS

The construction of porous β-cyclodextrin polymer (β-CDP) modified flower-like Fe₃O₄ particles (CDP@Fe₃O₄) is expected to remove various organic pollutants from water, based on the larger specific surface area of flower-like Fe₃O₄ particles and the active sites provided by β-CDP. With the help of various noncovalent interactions, the removal ability of CDP@Fe₃O₄ for various water-soluble and water-insoluble organic pollutants were systematically studied.

EXPERIMENTS

CDP@Fe₃O₄ were successfully synthesized and applied for the simultaneous removal of various organic pollutants with different electrical properties, structure and hydrophobicity. Adsorption efficiency, adsorption process, adsorption mechanism and the reusability of CDP@Fe₃O₄ for single pollutant and mixed pollutants were comprehensively investigated.

FINDINGS

CDP@Fe₃O₄ exhibited excellent adsorption capabilities for various pollutants. Importantly, when these pollutants were coexisting, CDP@Fe₃O₄ still maintained a comparable removal ability for various pollutants. Efficient removal of organic pollutants was attributed to varieties of noncovalent interactions between organic pollutants and CDP@Fe₃O₄, including hydrophobic interactions, hydrogen bonds, π-π and electrostatic interactions. These results revealed that the excellent adsorption ability and convenient regeneration make CDP@Fe₃O₄ being a potential candidate in various complex organic wastewater purification.

Self-Nitrogen-Doped Nanoporous Carbons Derived from Poly(1,5-diaminonaphthalene) for the Removal of Toxic Dye Pollutants from Wastewater: Non-Linear Isotherm and Kinetic Analysis

The high surface area and porosity of self-nitrogen-doped porous carbons (SNPCs) nominates them for potential application in water treatment due to their high efficiency towards the removal of various pollutants. In this study, SNPCs were fabricated from poly(1,5-diaminonaphthalene) (P(1,5-DANPh) by single and simultaneous carbonization at the activation step at different temperatures (600, 700, and 800 °C). The carbonization's temperature plays a vital role in controlling the nitrogen-doping, surface area, porosity, and morphology of SNPCs. The SNPCs-7 sample prepared at 700 °C showed the highest surface area (1678.8 m² g^-1) with pore volume (0.943 cm³ g^-1) with a micro/meso porous structure. The prepared SNPCs were used as an effective adsorbent for removal of crystal violet dye (CV) from contaminated water. SNPCs-7 showed the highest adsorption of 487.53 mg g^-1 and the adsorption capacity of the SNPCs samples follows the order SNPCs-7 > SNPCs-8 > SNPCs-6, which is consistent with the results of their surface area and porosity. The adsorption for CV dye followed Freundlich isotherm models and a pseudo second order kinetic model. The negative values of Gipps free energy (ΔG°) and positive value of enthalpy (ΔH°) indicated that the adsorption of CV dye onto the surface of SNPCs was a spontaneous and endothermic process, respectively. Based on the results, the adsorption mechanism of CV dye onto the surface of SNPCs was proposed.

Evaluation of Ocotea puberula bark powder (OPBP) as an effective adsorbent to uptake crystal violet from colored effluents: alternative kinetic approaches

The Ocotea puberula bark powder (OPBP) was evaluated as an effective adsorbent for the removal of crystal violet (CV) from colored effluents. OPBP was characterized and presented a surface with large cavities, organized as a honeycomb. The main functional groups of OPBP were O-H, N-H, C=O, and C-O-C. The adsorption of CV on OPBP was favorable at pH 9 with a dosage of 0.75 g L^-1. The Avrami model was the most suitable to represent the adsorption kinetic profile, being the estimated equilibrium concentration value of 3.37 mg L^-1 for an initial concentration of 50 mg L^-1 (CV removal of 93.3%). The equilibrium was reached within 90 min. The data were better described by the Langmuir isotherm, reaching a maximum adsorption capacity of 444.34 mg g^-1 at 328 K. The Gibbs free energy ranged from - 26.3554 to - 27.8055 kJ mol^-1, and the enthalpy variation was - 11.1519 kJ mol^-1. The external mass transfer was the rate-limiting step, with Biot numbers ranging from 0.0011 to 0.25. Lastly, OPBP application for the treatment of two different simulated effluents was effective, achieving a removal percentage of 90%.

Experimental investigation of activated carbon prepared from apricot stones material (ASM) adsorbent for removal of malachite green (MG) from aqueous solution

The adsorption of malachite green onto activated carbon prepared from apricot stones material has been investigated at batch conditions. The effects of contact time (0–60 min), initial pH (3–11), agitation speed (100–700 r/min), temperature (298–343 K), adsorbent dose (1–10 g/L), and malachite green concentration (4.45–17.6 mg/L) on the malachite green adsorption by apricot stones material have been studied. Malachite green removal increases over the contact time until equilibrium. The batch adsorption experiments were carried out to optimize the physical parameters on the malachite green removal efficiency. It has been found that 23.80 mg/g at 25°C and 88.05 mg/g at 70°C were removed. The kinetic parameters, rate constants and equilibrium adsorption capacities, were calculated and discussed for each kinetic model. The adsorption of malachite green onto apricot stones material is well described by the pseudo second-order equation. The experimental isotherm data were analyzed by different models; the adsorption follows the Langmuir model, providing a better fit of the equilibrium data. The thermodynamics parameters such as the negative free energy Δ G° (−0.191 to −4.447 kJ/mol) and positive enthalpy Δ H° (50.86 kJ/mol) indicated the spontaneous and endothermic nature of the malachite green adsorption with a chemisorption process.

Shapeable Aerogels of Metal-Organic-Frameworks Supported by Aramid Nanofibrils for Efficient Adsorption and Interception

The immobilization of the metal-organic frameworks (MOFs) on aerogels has risen to be a promising approach for the combination of advantages on both sides. Shapeable MOF hybrid aerogels were obtained by the growth of MOF crystals on aramid nanofibril (ANF) aerogels to retain high porosities, crystal structures, and original stabilities of individual MOFs and the mechanical robustness, flexibility, and low density of ANFs. The MOF hybrid aerogels exhibited superior adsorption performance for organic dyes (e.g., 113.8 mg/g for methyl violet and 107 mg/g of rhodamine B), offered a simple, efficient, and extensible platform for removing organic dyes from aqueous solution continuously, with high flux (620 L/(h·m²·bar) at a thickness of ∼0.87 mm) and excellent rejection (>98%). This work provided a practicable pathway to manage MOF crystals into a shapeable and recyclable form for extended applications in wide fields.

Core/shell hybrid fiber with aminated PAN and Fe2O3 as a high-capacity adsorbent for phosphate ions

APANF@Fe₂O₃, a phosphate adsorbent, was synthesized in two steps: the immobilization of an amine group onto polyacrylonitrile fiber (PANF) and the adsorption of an iron ion on aminated PANF (APANF). The amination degree of the PANF was adjusted considering its mechanical properties. The Fe₂O₃ on the surface of the APANF played a role as a phosphate-grasping layer via a ligand-exchange reaction. The APANF@Fe₂O₃ showed a considerable PO₄^3- adsorption amount of ca. 6 mmol/g at a low pH region (ca. 2-7) and 3 mmol/g at a high pH region (ca. 8-12). The adsorption data were interpreted with various kinetic and isotherm models. The Langmuir model was more suitable than the Freundlich and Redlich-Peterson models to fit the experimental data of the phosphate adsorption on the APANF@Fe₂O₃ and the pseudo-second-order model was better matched than the pseudo-first-order and Elovich's models. The results of this study demonstrate that the surface of the fibrous adsorbent was homogenous and the phosphate adsorption behavior of the APANF@Fe₂O₃ followed a simultaneous chemisorption process into the Fe₂O₃ layer.

Enhanced Adsorptive Properties and Pseudocapacitance of Flexible Polyaniline-Activated Carbon Cloth Composites Synthesized Electrochemically in a Filter-Press Cell

Electrochemical polymerization is known to be a suitable route to obtain conducting polymer-carbon composites uniformly covering the carbon support. In this work, we report the application of a filter-press electrochemical cell to polymerize polyaniline (PAni) on the surface of large-sized activated carbon cloth (ACC) by simple galvanostatic electropolymerization of an aniline-containing H₂SO₄ electrolyte. Flexible composites with different PAni loadings were synthesized by controlling the treatment time and characterized by means of Scanning Electron microscopy (SEM), X-Ray Photoelectron Spectroscopy (XPS), physical adsorption of gases, thermogravimetric analysis (TGA), cyclic voltammetry and direct current (DC) conductivity measurements. PAni grows first as a thin film mostly deposited inside ACC micro- and mesoporosity. At prolonged electropolymerization time, the amount of deposited PAni rises sharply to form a brittle and porous, thick coating of nanofibrous or nanowire-shaped structures. Composites with low-loading PAni thin films show enhanced specific capacitance, lower sheet resistance and faster adsorption kinetics of Acid Red 27. Instead, thick nanofibrous coatings have a deleterious effect, which is attributed to a dramatic decrease in the specific surface area caused by strong pore blockage and to the occurrence of contact electrical resistance. Our results demonstrate that mass-production restrictions often claimed for electropolymerization can be easily overcome.

Synthesis of nanocomposites using xylan and graphite oxide for remediation of cationic dyes in aqueous solutions

Due to the rapid development of industrialization, the water resources on which we depend are facing unprecedented challenges. Dyes, as an indispensable substance in our lives, have caused great pollution to the water resources in nature, and the removal of dyes from wastewater is becoming an important topic. A porous xylan/poly(acrylic acid)/graphite oxide nanocomposite was prepared by graft polymerization and used for adsorption of cationic ethyl violet dye in wastewaters in this paper. Various techniques, i.e., Fourier-transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, elemental analysis, scanning electron microscopy, and ultraviolet-visible spectroscopy, were used to study this composite. Adsorption isotherm measurements showed that the composite's adsorption behavior fits the Langmuir isotherm adsorption model. Adsorption tests showed that this material has excellent adsorption properties; the maximum adsorption capacity for ethyl violet dye was 273.99 mg/g. Investigation of the adsorption mechanism indicated that electrostatic forces and π-π effects are mainly involved in adsorption. Desorption cycling tests showed that the adsorption efficiency of the composite was still over 95% after 3 cycles. These results show that this porous xylan/poly (acrylic acid)/graphite oxide nanocomposite has potential applications in cationic dye removal.

An Easy Synthesis for Preparing Bio-Based Hybrid Adsorbent Useful for Fast Adsorption of Polar Pollutants

For the first time, γ-Al₂O₃ and Bio-Based Substances (BBS) hybrids (A-BBS) were prepared through a simple electrostatic interaction occurring between alumina, used as a support, and BBS (Bio-Based Substance from composted biowastes) carrying positive and negative charges, respectively. We evaluated the optimal amount of BBS to be immobilized on the support and the stability of the resulting A-BBS in order to use this novel hybrid material as an adsorbent for the removal of polar pollutants. Characterization was carried out by X-Ray Diffraction (XRD) for evaluating the crystal structure of the support, Fourier transform infrared spectroscopy (FT-IR) to evidence the presence of BBS on the hybrid material, thermogravimetric analysis (TGA) to measure the thermal stability of the hybrid materials and quantify the BBS amount immobilized on the support, N₂ adsorption at 77 K for the evaluation of the surface area and porosity of the systems, Zeta potential measurements to evaluate the effect of BBS immobilization on the surface charge of the particles and choose the substrates possibly interacting with them. Firstly, we tested the adsorption capability of three samples differently coated with BBS toward cationic species considering various adsorbate/adsorbent ratio. Crystal Violet (CV) was chosen as model pollutant to compare the performance of the hybrid materials with those of other materials described in the literature. The adsorption data were modeled by Langmuir and Freundlich adsorption isotherms. Then, we studied the adsorption capability of the developed material towards molecules with different structures; for this purpose, two contaminants of emerging concerns (carbamazepine and atenolol) were tested. The results indicate that A-BBS could be applied in wastewater treatment for the removal of a significant amount of polar species. In addition, a comparison with literature data concerning CV adsorption was carried out in order to evaluate the environmental impact of synthetic routes used to prepare different adsorbents.

Response surface methodology directed synthesis of luminescent nanocomposite hydrogel for trapping anionic dyes

The present research work reveals semi-interpenetrating network (semi-IPN) synthesis using response surface methodology-central composite design (RSM-CCD) based optimization. The maximum swelling of 362.11% was obtained with monomer, crosslinker and initiator concentrations 4.39 mol L^-1, 1.52 mol L^-1 and 4.58 mol L^-1, respectively, temperature 70 °C, time 3 h and pH 4.0. The synthesized hydrogel showed 94.16% and 95.62% removal for eosin yellow (EY) and eriochrome black-T (EBT) dyes, respectively. The incorporation of cadmium sulphide nanodots into the hydrogel network enhanced the % dye removal (96.82% EY and 98.73% EBT) along with fluorescent behavior. Various conditions optimized for EY and EBT dye removal with respect to semi-IPN were: 0.4 g adsorbent dose each, dye concentrations 10 mg L^-1 and 120 mg L^-1, contact time 24 h each, respectively. Adsorption studies followed langmuir theory for both dyes. Second order and first order kinetics along with intraparticle diffusion of dye molecules were favorable to EY and EBT, respectively. Thermodynamic study reveals exothermic nature of adsorption. Recyclability of the adsorbent is superior as tested by desorption-adsorption tests.

Shanshory AA, Soliman HMA, Aly HF. Decontamination of organic pollutants from aqueous media using cotton fiber–graphene oxide composite, utilizing batch and filter adsorption techniques: a comparative study

Cotton fiber–graphene oxide (C–GO) composite with high adsorptive properties towards the cationic dye, crystal violet (CV), was successfully fabricated by simple mixing of cotton fiber and GO in aqueous solution using a homogenizer. The as-prepared composite was characterized using TEM, SEM, LOM, XRD, FTIR, Raman and TGA. The characterization indicated that the formation of a homogeneous composite occurred via adequate mixing of the cotton fiber and GO. The fine structure of the obtained composite was successfully used in two adsorption techniques, namely batch adsorption and filter adsorption. Various parameters affecting batch adsorption, such as contact time, dye concentration, composite dose, NaCl dose, temperature and pH were investigated. In the filter adsorption mode, dye concentration, composite dose, NaCl dose, temperature, flow rate and pH were studied. A comparison study between the two techniques, i.e., batch adsorption and filter adsorption, are reported. The filter adsorption technique shows higher adsorption efficiency than the batch one, which was evident from the maximum adsorption capacity (Q°) values, obtained from the Langmuir isotherm. Further, the filter technique was developed and evaluated. This was achieved by regeneration, scaling-up and, finally, using another model of cationic dye (methylene blue).

Cotton fiber–graphene oxide (C–GO) composite with high adsorptive properties towards the cationic dye, crystal violet (CV), was successfully fabricated by simple mixing of cotton fiber and GO in aqueous solution using a homogenizer.