Adsorptive removal of organic pollutant methylene blue using polysaccharide-based composite hydrogels

Development of banana pseudo stem cellulose fiber based magnetic nanocomposite as an adsorbent for dye removal

A hybrid hydrogel nanocomposite derived from cellulose fiber extracted from Banana Pseudo Stem (BPS) was developed as an adsorbent material for wastewater treatment. The hydrogel was developed by graft copolymerization of N-hydroxyethylacrylamide on Cellulose Fiber (BPSCF-g-PHEAAm) with potassium peroxodisulphate (KPS) as an initiator and N, N'-methylene bisacrylamide (MBA) as a crosslinker using microwave irradiation. Magnetic nanoparticles generated by an in-situ method were incorporated into the network structure. Fourier Transform Infrared Spectroscopy (FTIR), Powder X-ray Diffraction (XRD), Thermogravimetric analysis (TGA), Vibrating Sample Magnetometer (VSM), Brunauer-Emmett-Teller analysis (BET), Field Emission Scanning Electron Microscopy (FESEM), and Energy Dispersive Spectrometer (EDS) were employed. The adsorption capacities of hydrogel and its nanocomposite were evaluated using Methylene Blue (MB) and Crystal Violet (CV) as model dyes. The parent gel exhibited the maximum absorption capacity of 235, and 219 mg g-1 towards MB and CV respectively which was enhanced to 320 and 303 mg g-1 for the nanocomposite. Adsorption data were best fitted with the pseudo-second-order kinetic model and the Freundlich isotherm model. Negative ΔG° and positive ΔH° indicated spontaneous and endothermic adsorption. Desorption was effective to an extent of 99 % in the HCl medium suggesting high reusability potential of the developed adsorbent material.

Strong, tough, conductive and transparent nanocellulose hydrogel based on Ca2+-induced cross-linked double-networks and its adsorption of methylene blue dye

A novel multi-performance SHNC/SA/CaCl2 hydrogel with multi-performance was prepared via ultra-low-temperature freeze-thaw cycling and Ca2+ cross-linking for the removal of methylene blue (MB) from industrial wastewater. Various methods were used to characterize the structure and properties of hydrogel, and the internal structure of hydrogel showed a three-dimensional network with hydrogen and ester bonds. The SHNC/SA/CaCl2-15 hydrogel exhibited the highest tensile properties (elongation = 800 %), viscoelasticity (90 kPa), compressive strength (0.45 MPa), tensile strength (0.47 MPa) and ionic conductivity (4.34 S/cm). The maximum adsorption capacity of 2 g SHNC/SA/CaCl2-15 hydrogel was 608.49 mg/g at 40 °C, pH = 8 and adsorption 24 h. The adsorption process of hydrogel toward MB was more consistent with the second-order kinetic model and Langmuir isothermal adsorption model. According to the Langmuir isotherm model, the maximum monolayer adsorption capacity of SHNC/SA/CaCl2-15 hydrogel toward MB can reach 613.88 mg/g. Finally, it was found that the removal rate of SHNC/SA/CaCl2-15 hydrogel for MB was still as high as 90 % after five cycles of the adsorption-desorption test, and it could be reused. The hydrogel can be used as cheap and reusable adsorption material for cationic dyes. Our study provides a new perspective for the development of multifunctional cellulose hydrogel adsorbent materials.

Green synthesis of biomass-derived carbon quantum dots for photocatalytic degradation of methylene blue

Water pollution, significantly influenced by the discharge of synthetic dyes from industries, such as textiles, poses a persistent global threat to human health. Among these dyes, methylene blue, particularly prevalent in the textile sector, exacerbates this issue. This study introduces an innovative approach to mitigate water pollution through the synthesis of nanomaterials using biomass-derived carbon quantum dots (CQDs) from grape pomace and watermelon peel. Utilizing the hydrothermal method at temperatures between 80 and 160 °C over periods ranging from 1 to 24 h, CQDs were successfully synthesized. A comprehensive characterization of the CQDs was performed using UV-visible spectroscopy, Fourier-transform infrared spectroscopy, dynamic light scattering, Raman spectroscopy, and luminescence spectroscopy, confirming their high quality. The photocatalytic activity of the CQDs in degrading methylene blue was evaluated under both sunlight and incandescent light irradiation, with measurements taken at 20 min intervals over a 2 h period. The CQDs, with sizes ranging from 1-10 nm, demonstrated notable optical properties, including upconversion and down-conversion luminescence. The results revealed effective photocatalytic degradation of methylene blue under sunlight, highlighting the potential for scalable production of these cost-effective catalytic nanomaterials for synthetic dye degradation.

Photodecoration of tungsten oxide nanoparticles onto eggshell as an ultra-fast adsorbent for removal of MB dye pollutant

Nowadays, the use of natural wastes and adsorbents along with their modification by simple and new methods based on metal oxides to remove dye pollutants has been the focus of many researchers. In this study, for the first time, simple and low-cost modification of eggshell (EGS) with tungsten oxide (WO3) based on the photochemical modification method as a green, ultra-fast, cost-effective, and biodegradable adsorbent is reported to remove of methylene blue (MB) dye pollutant. The EGS modified by WO3 was investigated by EDX, EDX mapping, XRD, FE-SEM, and UV-Vis Diffuse Reflectance (DRS) analyses. The obtained results show that the modified EGS by WO3 has more than ten times (78.5%) the ability to remove MB dye pollutant within 3 min compared to bare EGS (11%). Various parameters including dye pollutant pH, dye concentration, adsorbent dosage, and reusability of the WO3/EGS adsorbent for removal of MB dye pollutant were investigated and the result show that the adsorbent capacity of WO3/EGS is 1.64 mg g-1. EGS adsorbent The synthesis of WO3/EGS adsorbent with a novel photochemical method as a fast and very cheap adsorbent with excellent efficiency can be a promising alternative adsorbent for various purposes in removing dye pollutants from water environments.

Biopolymer-based beads for the adsorptive removal of organic pollutants from wastewater: Current state and future perspectives

Among biopolymer-based adsorbents, composites in the form of beads have shown promising results in terms of high adsorption capacity and ease of separation from the effluents. This review addresses the potential of biopolymer-based beads to remediate wastewaters polluted with emerging organic contaminants, for instance dyes, active pharmaceutical ingredients, pesticides, phenols, oils, polyaromatic hydrocarbons, and polychlorinated biphenyls. High adsorption capacities up to 2541.76 mg g-1 for dyes, 392 mg g-1 for pesticides and phenols, 1890.3 mg g-1 for pharmaceuticals, and 537 g g-1 for oils and organic solvents have been reported. The review also attempted to convey to its readers the significance of wastewater treatment through adsorption by providing an overview on decontamination technologies of organic water contaminants. Various preparation methods of biopolymer-based gel beads and adsorption mechanisms involved in the process of decontamination have been summarized and analyzed. Therefore, we believe there is an urge to discuss the current state of the application of biopolymer-based gel beads for the adsorption of organic pollutants from wastewater and future perspectives in this regard since it is imperative to treat wastewater before releasing into freshwater bodies.

Feasibility evaluation of near dissolved organic matter microfiltration (NDOM MF) for the efficient removal of microplastics in the water treatment process

Microfiltration (MF) using membranes with a mean pore size smaller than 0.45 μm has generally been used for particle removal from water, given that materials larger and smaller than 0.45 μm are regarded as particulates and dissolved organic matter (DOM), respectively. It is also the case for removing small-size microplastics (MPs). However, given their sizes (ca. 1 μm), there is room for further improvement of the productivity (i.e., water flux) in the pore size range of 0.45-1 μm on the condition that the removal rate is maintained. With this in mind, MF's water flux and removal rate were tested using seven different MF membranes, and the right pore, with the size of 0.8 μm, was found for MP removal, which is called near DOM (NDOM) MF. In the filtration test using polystyrene surrogate beads with an average particle diameter of 1.20 μm, NDOM MF exhibited a 1.7 to 13 times higher permeate flux than the conventional MF using 0.1, 0.2, and 0.45 μm membranes while maintaining a higher removal rate than 2 log. The excellent removal rate of the NDOM MF was attributable to the following three factors: (1) smaller mean pore size than the average particle diameter, (2) particle screening effect enhanced by the secondary layer formed by surface deposition, and (3) 3D mesh sublayer structure favorable for capturing penetrated particles. Furthermore, the outstanding filtration performance also appeared in a low-temperature (< 10°C) process, demonstrating that NDOM MF is feasible independently of temperature. Additionally, in constant flux filtration, NDOM MF demonstrated the long-term feasibility by lowering the transmembrane pressure and specific filtration energy by more than 2 times.

Removal of Methylene Blue Dye from Aqueous Solutions Using Polymer Inclusion Membrane Containing Calix[4]pyrrole

The effective purification of aqueous solutions of methylene blue dye was tested using polymer inclusion membranes (PIMs) that contained cellulose triacetate (CTA) as a polymer base, o-nitrophenyl octyl ether (o-NPOE) as a plasticizer, and meso-tetra methyl tetrakis-[methyl-2-(4-acetlphenoxy)] calix[4]pyrrole (KP) as a carrier. Scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy were used to define the microstructure and surface of PIMs. Experimental results showed that, with an increased concentration of methylene blue in an aqueous solution, the removal percentage also increased. Further observation showed that the flux increased with the rise in the source phase pH values from 3 to 10. The carrier and plasticizer content in the membrane significantly influenced the membrane's transport properties. The optimal composition of the membrane in percent by weight for KP was 74% plasticizer; 18% support, and 8% carrier. The maximum MB removal (93.10%) was achieved at 0.10 M HCl solution as the receiving phase. It was shown that the membrane with optimal composition showed good reusability and enabled the easy and spontaneous separation of methylene blue from aqueous solutions.

Rational synthesis of two isostructural thiophene-containing metal-organic frameworks toward photocatalytic degradation of organic pollutants

In this work, thiophene moieties (as the crucial functional groups) have been successfully incorporated into the skeleton of metal-organic frameworks (MOFs) by using thienyl-substituted triazole ligands. Reaction of AgCF3SO3 with 3-phenyl-5-(2-thienyl)-1,2,4-triazole (PTTzH) or 3,5-bis(2-thienyl)-1,2,4-triazole (BTTzH) afforded two isostructural MOFs (AgTz-3 and AgTz-4) in gram-scale. AgTz-4 with higher thiophene content showed significantly stronger photocatalytic activity than AgTz-3 with lower thiophene content. Noteworthy, the photodegradation rate constants of AgTz-4 were 0.055 mg·L-1·min-1 for rhodamine B and 0.24 min-1 for salazosulfapyridine, which is comparable or even higher than some MOF-based materials reported in the literature. More importantly, AgTz-4 demonstrated good reusability and stability after four cycles of photodegradation. Our experimental results revealed that the enhanced photodegradation efficiency can be attributed to the increased light absorption capacity and optimized band structure of Ag-MOFs resulting from the introduction of thiophene groups into MOF structures.

Enhanced dye sequestration with natural polysaccharides-based hydrogels: A review

Due to the expansion of industrial activities, the concentration of dyes in water has been increasing. The dire need to remove these pollutants from water has been heavily discussed. This study focuses on the reproducible and sustainable solution for wastewater treatment and dye annihilation challenges. Adsorption has been rated the most practical way of the several decolorization procedures due to its minimal initial investment, convenient utility, and high-performance caliber. Hydrogels, which are three-dimensional polymer networks, are notable because of their potential to regenerate, biodegrade, absorb bulky amounts of water, respond to stimuli, and have unique morphologies. Natural polysaccharide hydrogels are chosen over synthetic ones because they are robust, bioresorbable, non-toxic, and cheaply accessible. This study has covered six biopolymers, including chitosan, cellulose, pectin, sodium alginate, guar gum, and starch, consisting of their chemical architecture, origins, characteristics, and uses. The next part describes these polysaccharide-based hydrogels, including their manufacturing techniques, chemical alterations, and adsorption effectiveness. It is deeply evaluated how size and shape affect the adsorption rate, which has not been addressed in any prior research. To assist the readers in identifying areas for further research in this subject, limitations of these hydrogels and future views are provided in the conclusion.

Chitosan coated biomass waste-based magnetic hydrogel beads for the removal of methylene blue

Due to developing technology and increasing population, human needs have increased, and textile activities have gained momentum. Many synthetic dyestuffs are used to meet the needs in this field. In this study, a cheap, useful, innovative, environmentally friendly and sustainable adsorbent was developed for the removal of Methylene Blue(MB), which is one of the dyes that is harmful to the environment. In the cultivation of fruit trees, in addition to the product, very high amounts of by-products/waste (garbage, branches, bark, leaves, etc.) are produced. In this direction, fig tree wastes were immobilized with chitosan, made magnetic, and MB adsorption on the developed adsorbent was examined in a batch system. Glutaraldehyde was used as crosslinker. Characterization of synthesized glutaraldehyde cross-linked chitosan-coated magnetic vegetable waste composite beads (g-CMBW) was carried out by SEM, EDX, FTIR and XRD. In the study, the effects of temperature (25-55 °C), pH (3.0-8.0), initial MB concentration (10-250mg/L), contact time (5-360min) and the amount of adsorbent (2-10 g/L) on MB adsorption with g-CMBW were examined. The optimum conditions obtained were determined as pH 6.0, temperature 25 °C, adsorbent amount 6 g/L, and contact time 120 min. The maximum adsorption capacity in MB removal using g-CMBW composite beads was calculated as 103.1 mg/g according to the Langmuir isotherm model. The temperature studies showed that the adsorption capacity decreased with increasing temperature, showing that the system was exothermic. In light of these results, it was determined that there are new promising adsorbents of natural origin, with higher adsorption capacity, lower cost, and alternatives to commercially used adsorbents in the removal of MB from aqueous media.

aPDI meets PPE: photochemical decontamination in healthcare using methylene blue-where are we now, where will we go?

Personal protective equipment (PPE) reuse, first recommended in the context of the SARS-CoV-2 pandemic, can mitigate shortages in crisis situations and can greatly reduce the environmental impact of typically single-use PPE. Prior to safe reuse, PPE must be sanitized and contaminating pathogens-in current circumstances viruses in particular-must be inactivated. However, many established decontamination procedures are not equitable and remain unavailable in low-resource settings. In mid-2020, an interdisciplinary consortium of researchers first studied the potential of implementing cheap and easy-to-use antimicrobial photodynamic inactivation (aPDI) using methylene blue as photosensitizer to decontaminate face masks and filtering facepiece respirators. In this perspective piece, we describe the development of this novel method, discuss recent advances, and offer insights into how equitable PPE decontamination via methylene blue-based aPDI may be integrated into circular economy policies in the healthcare sector.

Hemicelluloses hydrogel: Synthesis, characterization, and application in dye removal

Novel materials using biowaste as adsorbents in wastewater treatment have been allocated considerable interest. Herein, we present the synthesis of different hydrogels of crosslinked polyacrylamide in presence of hemicelluloses with/ without bentonite, using a soft reaction condition. The structure of new hydrogels was characterized by spectroscopic, thermal and microscopic experiments. The semi-interpenetrated network with hemicelluloses: 10 %; acrylamide 79 %; bentonite 10 %; N,N,N',N'-tetramethylethylenediamine: 1 % allows reducing 20 % the use of non-renewable acrylamide, without changing its decomposition temperatures and keeping its water absorption capacity. This hydrogel was applied to dye removals, such as rhodamine B, methylene red and methylene blue in aqueous solutions. In the case of methylene blue, highest removal is observed with maximum adsorption of qmax = 140.66 mg/g, compared to material without hemicelluloses that only a qmax = 88.495 mg/g. The adsorption kinetics and equilibrium adsorption isotherms are in accordance with the pseudo-second-order kinetic model and Langmuir isotherm model, respectively. The developed hydrogel from hemicelluloses represents a potential alternative adsorbent for a sustainable system of sewage treatment.

A review of physical, chemical and biological synthesis methods of bimetallic nanoparticles and applications in sensing, water treatment, biomedicine, catalysis and hydrogen storage

This article provides an in-depth analysis of various fabrication methods of bimetallic nanoparticles (BNP), including chemical, biological, and physical techniques. The review explores BNP's diverse uses, from well-known applications such as sensing water treatment and biomedical uses to less-studied areas like breath sensing for diabetes monitoring and hydrogen storage. It cites results from over 1000 researchers worldwide and >300 peer-reviewed articles. Additionally, the article discusses current trends, actionable recommendations, and the importance of synthetic analysis for industry players looking to optimize manufacturing techniques for specific applications. The article also evaluates the pros and cons of various fabrication methods, highlighting the potential of plant extract synthesis for mass production of capped BNPs. However, it warns that this method may not be suitable for certain applications requiring ligand-free surfaces. In contrast, physical methods like laser ablation offer better control and reactivity, especially for applications where ligand-free surfaces are critical. The report underscores the environmental benefits of plant extract synthesis compared to chemical methods that use hazardous chemicals and pose risks to extraction, production, and disposal. The article emphasizes the need for life cycle assessment (LCA) articles in the literature, given the growing volume of research on nanotechnology materials. This article caters to researchers at all stages and applies to various fields applying nanomaterials.

Advances in gum-based hydrogels and their environmental applications

Gum-based hydrogels (GBHs) have been widely employed in diverse water purification processes due to their environmental properties, and high absorption capacity. More desired properties of GBHs such as biodegradability, biocompatibility, material cost, simplicity of manufacture, and wide range of uses have converted them into promising materials in water treatment processes. In this review, we explored the application of GBHs to remove pollutants from contaminated waters. Water resources are constantly being contaminated by a variety of harmful effluents such as heavy metals, dyes, and other dangerous substances. A practical way to remove chemical waste from water as a vital component is surface adsorption. Currently, hydrogels, three-dimensional polymeric networks, are quite popular for adsorption. They have more extensive uses in several industries, including biomedicine, water purification, agriculture, sanitary products, and biosensors. This review will help the researcher to understand the research gaps and drawbacks in this field, which will lead to further developments in the future.

Enhanced Sorption Performance of Natural Zeolites Modified with pH-Fractionated Humic Acids for the Removal of Methylene Blue from Water

This work explores the effect of humic acids (HA) fractionation on the sorption ability of a natural zeolite (NYT)-HA adduct. HA were extracted from compost, fractionated via the pH fractionation method, and characterized via UV-Vis spectroscopy and gel permeation chromatography. The HA samples were immobilized onto NYT via thermal treatment. The resulting adducts (NYT-HA) were tested for their ability to remove methylene blue (MB) from an aqueous solution. It was found that the sorption performance of NYT-HA strongly depends on the chemical characteristics of humic acids. Sorption capacity increased with the molecular weight and hydrophobicity degree of the HA fractions. Hydrophobic and π-π interactions are likely the primary mechanisms by which MB interacts with HA. The sorption kinetic data conform to the pseudo-second-order model. The Freundlich isotherm model adequately described the sorption equilibrium and revealed that the uptake of MB onto NYT-HA is endothermic in nature.

A critical review on the removal of toxic pollutants from contaminated water using magnetic hybrids

The persistence of organic/inorganic pollutants in the water has become a serious environmental issue. Among the different pollutants, dyes and heavy metal pollution in waterways are viewed as a global ecological problem that can have an impact on humans, plants, and animals. The necessity to develop a sustainable and environmentally acceptable approach to remove these toxic contaminants from the ecosystem has been raised. In the past two decades, rapid industrialization and anthropogenic activities in developed countries have aggravated environmental pollution. Industrial effluents that are discharged directly into the natural environment taint the water, which has a consequence for the water resources. Magnetic nanohybrids are broadly investigated materials used in the adsorption and photocatalytic degradation of poisonous pollutants present across water effluents. In the present review, the toxic health effects of heavy metals and dyes from the water environment have been discussed. This paper reviews the role of magnetic nanohybrids in the removal of pollutants from the water environment, providing an adequate point of view on their new advances regarding their qualities, connection methodologies, execution, and their scale-up difficulties.

Sustainable remediation of dye-contaminated wastewater using novel cross-linked Hex-CCP-co-PPT microspheres

The presence of dyes in contaminated water poses substantial dangers to the health of both humans and aquatic life. A process called precipitation polymerization was used to create unique cross-linked hexa-chlorocyclotriphosphazene-co-phenolphthalein (Hex-CCP-co-PPT) microspheres for the purpose of this research. Advanced methods such as X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and differential thermogravimetry (DTG) were used to characterise these microspheres. In a simulated solution, the performance of Hex-CCP-co-PPTs as a sorbent for removing MB dye was investigated, and the results showed an unprecedentedly high removal rate of 88.4% for MB. Temperature of 25 °C, a Hex-CCP-co-PPTs dose of 40 mg, an MB concentration of 20 ppm, an MB solution volume of 20 mL, a contact time of 40 min, and a pH of 9 were found to be the optimal experimental conditions. According to the results of the kinetic and adsorption analyses, the PSO and Langmuir adsorption models are the best ones to use. These models favour the chemi-sorption nature and mono-layered adsorption of MB in comparison to Hex-CCP-co-PPTs. Importantly, the thermodynamic analysis demonstrated that the process of removing MB by utilizing Hex-CCP-co-PPTs was endothermic and occurred spontaneously. These findings highlight the potential application of Hex-CCP-co-PPT microspheres in Algal Membrane Bioreactors (AMBRs) for the efficient and sustainable removal of dye from wastewater. This would contribute to the protection of ecosystems as well as the public's health.

Adsorption of Basic Yellow 28 and Basic Blue 3 Dyes from Aqueous Solution Using Silybum Marianum Stem as a Low-Cost Adsorbent

In the present study, the ability of an adsorbent (SLM Stem) obtained from the stem of the Silybum Marianum plant to treat wastewater containing the cationic dyes basic blue 3 (BB3) and basic yellow 28 (BY28) from aqueous solutions was investigated using a batch method. Then, the SLM Stem (SLM Stem-Natural) adsorbent was carbonized at different temperatures (200-900 °C) and the removal capacity of the products obtained for both dyes was examined again. The investigation continued with the product carbonized at 800 °C (SLM Stem-800 °C), the adsorbent with the highest removal capacity. The dyestuff removal studies were continued with the SLM Stem-Natural and SLM Stem-800 °C adsorbents because they had the highest removal values. The surface properties of these two adsorbents were investigated using IR, SEM, and XRD measurements. It was determined that the SLM Stem-Natural has mainly non-porous material, and the SLM Stem-800 °C has a microporous structure. The optimal values for various parameters, including adsorbent amount, initial dye solution concentration, contact time, temperature, pH, and agitation speed, were investigated for BY28 dye and were 0.05 g, 15 mg/L, 30 min, 40 °C, pH 6 and 100 rpm when SLM Stem-Natural adsorbent was used and, 0.15 g, 30 mg/L, 30 min, 40 °C, pH 10, and 150 rpm when SLM Stem-800 °C adsorbent was used. For BB3 dye, optimal parameter values of 0.20 g, 10 mg/L, 30 min, 25 °C, pH 7, and 100 rpm were obtained when SLM Stem-Natural adsorbent was used and 0.15 g, 15 mg/L, 40 min, 40 °C, pH 10, and 100 rpm when SLM Stem-800 °C adsorbent was used. The Langmuir isotherm described the adsorption process best, with a value of r2 = 0.9987. When SLM Stem-800 °C adsorbent was used for BY28 dye at 25 °C, the highest qm value in the Langmuir isotherm was 271.73 mg/g. When the study was repeated with actual water samples under optimum conditions, the highest removal for the BY28 dye was 99.9% in tap water with the SLM Stem-800 °C adsorbent. Furthermore, the reuse study showed the adsorbent's efficiency even after three repetitions.

Development of carboxymethyl cellulose-graphene oxide biobased composite for the removal of methylene blue cationic dye model contaminate from wastewater

Utilizing Glutaraldehyde crosslinked sodium carboxymethyl cellulose (CMC-GA) hydrogel and its nanographene oxide composite (CMC-GA-GOx), an effective carboxymethyl cellulose-graphene oxide biobased composites adsorbent was developed for the adsorption removal of methylene blue (MB) cationic dye contaminate from industrial wastewater. The CMC-GA-GOx composites developed were characterized using FTIR, RAMAN, TGA, SEM, and EDX analysis instruments. Through batch experiments, several variables affecting the removal of MB dye, including the biocomposites GO:CMC composition, adsorption time, pH and temperature, initial MB concentration, adsorbent dosage, and NaCl concentration, were investigated under different conditions. The maximum dye removal percentages ranged between 93 and 98%. They were obtained using biocomposites CMC-GA-GO102 with 20% GO weight percent, adsorption time 25 min, adsorption temperature 25 °C, MB concentrations 10-30 ppm, adsorption pH 7.0, and 0.2 g adsorbent dose. The experimental data of the adsorption process suit the Langmuir isotherm more closely with a maximal monolayer adsorption capacity of 76.92 mg/g. The adsorption process followed the kinetic model of pseudo-second order. The removal of MB was exothermic and spontaneous from a thermodynamic standpoint. In addition, thermodynamic results demonstrated that adsorption operates most effectively at low temperatures. Finally, the reusability of the developed CMC-GA-GO102 has been proved through 10 successive cycles where only 14% of the MB dye removal percentage was lost. These results suggest that the developed CMC-GA-GO102 composite may be an inexpensive and reusable adsorbent for removing organic cationic dyes from industrial wastewater.

Simultaneous adsorption of ciprofloxacin drug and methyl violet dye on boron nitride nanosheets: experimental and theoretical insights

In this study, hexagonal boron nitride (BN) with a sheet-like morphology is successfully synthesized by reacting borax (Na2B4O7·10H2O) and urea (CO(NH2)2) powders in air via a facile microwave-assisted method within a short reaction time (15 min). The as-prepared product is structurally characterized via Fourier transformation infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FESEM), energy dispersion X-ray analyzer (EDX), transmission electron microscopy (TEM), and Brunauer-Emmett-Teller (BET) surface area measurements. The adsorption process of methyl violet (MV) as a model of organic dyes and ciprofloxacin (CIP) as a model of antibiotics onto the boron nitride nanosheets has been experimentally and theoretically studied. The BN nanosheets exhibit the maximum adsorption capacity of 320.94 mg g-1 for MV dye and 266.29 mg g-1 for CIP antibiotic. The Freundlich isotherm model was suitable to describe the adsorption equilibrium isotherm data and the pseudo second-order model reflected the adsorption kinetics well. The calculated thermodynamic parameters show that the adsorption process is spontaneous under the measured conditions. The adsorption of CIP, MV and CIP + MV molecules on the surface of BN has been investigated through DFT calculations. The charge transfer and high adsorption capacity demonstrate the potential of BN nanosheets as an adsorbent for the simultaneous removal of MV dye and CIP drug from contaminated water.

Polysaccharide-based nanoassemblies: From synthesis methodologies and industrial applications to future prospects

Polysaccharides, due to their remarkable features, have gained significant prominence in the sustainable production of nanoparticles (NPs). High market demand and minimal production cost, compared to the chemically synthesised NPs, demonstrate a drive towards polysaccharide-based nanoparticles (PSNPs) benign to environment. Various approaches are used for the synthesis of PSNPs including cross-linking, polyelectrolyte complexation, and self-assembly. PSNPs have the potential to replace a wide diversity of chemical-based agents within the food, health, medical and pharmacy sectors. Nevertheless, the considerable challenges associated with optimising the characteristics of PSNPs to meet specific targeting applications are of utmost importance. This review provides a detailed compilation of recent accomplishments in the synthesis of PSNPs, the fundamental principles and critical factors that govern their rational fabrication, as well as various characterisation techniques. Noteworthy, the multiple use of PSNPs in different disciplines such as biomedical, cosmetics agrochemicals, energy storage, water detoxification, and food-related realms, is accounted in detail. Insights into the toxicological impacts of the PSNPs and their possible risks to human health are addressed, and efforts made in terms of PSNPs development and optimising strategies that allow for enhanced delivery are highlighted. Finally, limitations, potential drawbacks, market diffusion, economic viability and future possibilities for PSNPs to achieve widespread commercial use are also discussed.

An efficient and adsorption of methylene blue dye on a natural clay surface: modeling and equilibrium studies

The present research work revolves around the evaluation of the elimination of the cationic dye methylene blue (MB) from an aqueous solution by the exploitation of natural clay (TMG) from South-East Morocco. Several physicochemical techniques were used to characterize our TMG adsorbate, namely, X-ray diffraction, Fourier transform infrared absorption spectroscopy, differential thermal analysis, thermal gravimetric analysis, and zero charge point (pHpzc). The morphological properties and elemental composition of our material were identified using scanning electron microscopy coupled with an energy-dispersive X-ray spectrometer. The batch technique was used under different operating conditions to produce quantitative adsorption, namely, the amount of adsorbent, dye concentration, contact time, pH, and solution temperature. The maximum adsorption capacity of MB on TMG was 81.185 mg g^-1 for a concentration of 100 mg L^-1 MB at pH_initial = 6.43 (no initial adjustment of the pH-value was performed), temperature 293 K, and 1 g L^-1 adsorbent. The adsorption data were examined by Langmuir, Freundlich, and Temkin isotherms. The Langmuir isotherm provides the best correlation with the experimental data, and the pseudo-second-order kinetic model is more appropriate for the adsorption of the MB dye. The thermodynamic study of MB adsorption indicates that the process is physical, endothermic, and spontaneous. The Box-Behnken method was applied to identify the optimal conditions for MB removal in the design of batch experiments. The parameters examined result in >99% removal. The TMG material's regeneration cycles and low cost ($0.393 per gram) show that it is both environmentally friendly and very effective for dye removal in the various textile sectors.

Eco-Friendly Semi-Interpenetrating Polymer Network Hydrogels of Sodium Carboxymethyl Cellulose/Gelatin for Methylene Blue Removal

The present work describes the potential application of environmentally friendly sodium carboxymethylcellulose/gelatin (CMC/Gel) semi-interpenetrating hydrogels prepared by citric acid as a nontoxic cross-linking agent to adsorb dyes. The prepared hydrogels were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA/DTG), and swelling study. The adsorption performance of CMC/Gel2 (C/G2) hydrogel on methylene blue (MB) was investigated. The results showed the better adsorption conditions: adsorption time of 300 min, initial MB concentration of 500 mg/L, adsorbent dosage of 1.2 g/L, solution pH of 7, and temperature of 30 °C. The adsorption kinetics fit the pseudo-second order kinetics model, and the adsorption isotherm fit the Langmuir isotherm model. The maximum adsorption capacity reached 943.40 mg/g. The adsorption process is a spontaneous exothermic process. After three adsorption-desorption cycles, the removal rate of MB by hydrogel still reached 85%, with good reusability. Consequently, the hydrogel can be used as an environmentally friendly, stable, and efficient adsorbent for dyes in wastewater treatment.

Magnetic Ionotropic Hydrogels Based on Carboxymethyl Cellulose for Aqueous Pollution Mitigation

In this work, stabilized ionotropic hydrogels were designed using sodium carboxymethyl cellulose (CMC) and assessed as inexpensive sorbents for hazardous chemicals (e.g., Methylene Blue, MB) from contaminated wastewaters. In order to increase the adsorption capacity of the hydrogelated matrix and facilitate its magnetic separation from aqueous solutions, sodium dodecyl sulfate (SDS) and manganese ferrite (MnFe₂O₄) were introduced into the polymer framework. The morphological, structural, elemental, and magnetic properties of the adsorbents (in the form of beads) were assessed using scanning electron microscopy (SEM), energy-dispersive X-ray analysis, Fourier-transform infrared spectroscopy (FTIR), and a vibrating-sample magnetometer (VSM). The magnetic beads with the best adsorption performance were subjected to kinetic and isotherm studies. The PFO model best describes the adsorption kinetics. A homogeneous monolayer adsorption system was predicted by the Langmuir isotherm model, registering a maximum adsorption capacity of 234 mg/g at 300 K. The calculated thermodynamic parameter values indicated that the investigated adsorption processes were both spontaneous (ΔG < 0) and exothermic (ΔH < 0). The used sorbent can be recovered after immersion in acetone (93% desorption efficiency) and re-used for MB adsorption. In addition, the molecular docking simulations disclosed aspects of the mechanism of intermolecular interaction between CMC and MB by detailing the contributions of the van der Waals (physical) and Coulomb (electrostatic) forces.

Green synthesized hydroxyapatite for efficient immobilization of cadmium in weakly alkaline environment

The development of cost-effective passivators for the remediation of heavy metal-contaminated soils has been a research hotspot and an unsolved challenge. Herein, a novel hydroxyapatite (GSCH) was synthesized by co-precipitating distiller effluent-derived Ca with (NH₄)₂HPO₄ using straw-derived dissolved organic matter (S-DOM) as the dispersant. Batch adsorption experiments and soil incubation tests were performed to assess the immobilization efficiency of GSCH for Cd in weakly alkaline environments. As a result, GSCH showed an excellent adsorption efficiency to Cd with a maximum adsorption amount of ∼222 mg g^-1, which was fairly competitive compared to other similar previously materials reported. The kinetic data indicated that the adsorption of Cd on GSCH was a chemical and irreversible process, while the thermodynamic data revealed a spontaneous (ΔG° < 0) and endothermic (ΔH° > 0) adsorption process. Based on mechanism analysis, both physisorption (e.g., electrostatic attraction and pore filling) and chemisorption (e.g., ion exchange and complexation) were responsible for Cd adsorption on GSCH. Particularly, the incorporated S-DOM and hydroxyapatite phase in GSCH acted synergistically in the adsorption process. The incubation results showed that GSCH application could significantly reduce the bioavailability, phytoavailability and bioaccessibility of Cd in soil by 48.4%-57.8%, 20.4%-28.6% and 12.6%-24.0%, respectively. Moreover, GSCH application also improved soil bacterial communities and enhanced soil nutrient availability. Overall, this is the first study to demonstrate the potential application value of GSCH in Cd immobilization, providing promising insights into the development of green and cost-effective hydroxyapatite-based passivators for the remediation of heavy metal-contaminated soils.

Acid-induced Poria cocos alkali-soluble polysaccharide hydrogel: Gelation behaviour, characteristics, and potential application in drug delivery

Poria cocos alkali-soluble polysaccharide (PCAP), a water-insoluble β-glucan, is the main component of the total dried sclerotia of Poria cocos. However, its gelation behaviour and properties have yet to be comprehensively studied. In this study, an acid-induced physical hydrogel based on natural PCAP is fabricated. The acid-induced gelation in PCAP is explored with respect to the pH and polysaccharide concentration. PCAP hydrogels are formed in the pH range of 0.3-10.5, and the lowest gelation concentration is 0.4 wt%. Furthermore, dynamic rheological, fluorescence, and cyclic voltammetry measurements are performed to elucidate the gelation mechanism. The results reveal that hydrogen bonds and hydrophobic interactions play a dominant role in gel formation. Subsequently, the properties of the PCAP hydrogels are investigated using rheological measurements, scanning electron microscopy, gravimetric analysis, free radical scavenging, MTT assays, and enzyme-linked immunosorbent assays. The PCAP hydrogels exhibit a porous network structure and cytocompatibility, in addition to good viscoelastic, thixotropic, water-holding, swelling, antioxidant, and anti-inflammatory activities. Furthermore, using rhein as a model drug for encapsulation, it is demonstrated that its cumulative release behaviour from the PCAP hydrogel is pH dependent. These results indicate the potential of PCAP hydrogels for application in biological medicine and drug delivery.

Controlled design of Na-P1 zeolite/ porous carbon composites from coal gasification fine slag for high-performance adsorbent

Low-cost and concentrated industrial wastes have been recognized as a sustainable resource for preparation of new functional materials. Here, a new method was designed for the synthesis of porous composites containing high-purity Na-P1 zeolite and porous carbon from waste coal gasification fine slag (CGFS), which was treated first by acid leaching to controllably remove metal impurities and adjust Si/Al ratio, followed by NaOH fusion and hydrothermal treatment. By leaching with 1.0 mol/L HCl solution, the Si/Al ratio of the raw CGFS increased to 5.7, and the obtained CZ-1.0 consisted of high-purity Na-P1 zeolite with a typical cone-shaped flower cluster shape. The residue carbon in CGFS can be further activated to form porous carbon and graphite carbon layers interposed in the zeolite structure. The specific surface area and pore volume of CZ-1.0 reached 153.91 m²/g and 0.18 cm³/g, respectively. CZ-1.0 exhibited remarkable adsorption performance for methylene blue (MB) with the adsorption capacity reaching 137.5 mg/g for 100 mg/L MB solution. The adsorption process is mainly controlled by the chemisorption mechanism, and the adsorption of MB by CZ-1.0 may include ion exchange, hydrogen bond interaction, π-π bond interaction and van der Waals force. NaCl solution was successfully used as the desorption agent to regenerate the composite material, and the removal rate remained above 92% after five cycles. This work provides an effective strategy to synthesize a practically applicable adsorbent from the waste coal gasification fine slag for the purification of MB wastewater.

Recent developments of polysaccharide based superabsorbent nanocomposite for organic dye contamination removal from wastewater - A review

One of the main problems with water pollution is dye contamination of rivers, industrial effluents, and water sources. It has endangered the world's sources of drinking water. Several remediation strategies have been carefully developed and tested to minimize this ominous picture. Due to their appealing practical and financial benefits, adsorption methods in particular are often listed as one of the most popular solutions to remediate dye-contaminated water. Biopolymer-based hydrogel nanocomposites are a cutting-edge class of materials with a wide range of applications that are effective in removing organic dyes from the environment. Since the incorporation of various materials into hydrogel matrices generated composite materials with distinct characteristics, these unique materials were often alluded to as ideal adsorbents. The fundamental emphasis of the conceptual and critical review of the literature in this research is the significant potential of hydrogel nanocomposites (HNCs) to remediate dye-contaminated water (especially for articles from the previous five years). The review also provides knowledge for the development of biopolymer-based HNCs, prospects, and opportunities for future research. It is also focused on optimum conditions for dye adsorption processes along with their adsorption kinetics and isotherm models. In summary, the information gained in this review research may contribute to a strengthened scientific rationale for the practical and efficient application of these novel adsorbent materials.

Cold plasma-assisted regeneration of biochar for dye adsorption

Environmental remedies, including adsorption-based water purification, are now being asked to meet the requirement for a low-carbon circular economy requiring low energy and low material consumption. In this regard, we tested the possibility of regenerating adsorbents via cold plasma (CP) treatment for less use of adsorbents and no washing solution. In the adsorption of methylene blue (MB) using carbonized rice husk (CRH) and five successive regeneration cycles by CP treatment, the removal efficiencies were maintained at a moderate level (∼70% of the initial performance), unlike five consecutive adsorption without CP treatment (∼9-13% of the initial performance). The regeneration of CRH by CP treatment was also double-checked by the FESEM, EDS, BET, FTIR, XPS, and surface zeta potential measurements. The successfully recovered adsorption capability is related to the remediation of adsorption sites. It is also worth noting that the required power consumption for recycling by CP treatment was about 6.4 times lower than carbonizing new rice husks. This work provides insights into recovering adsorbents using CP without rigorous, costly, and energy-intensive processes.

Morphological guided sphere to dendrite BiVO4 for highly efficient organic pollutant removal and photoelectrochemical performance under solar light

Monoclinic BiVO₄ (m-BiVO₄) has been reported as promising phase for solar light driven photocatalysis. However, in the case of morphology guided BiVO₄ with different synthetic conditions maintaining the m-BiVO₄ phase remains a substantial challenge for achieving an efficient photocatalyst driven by solar light. Herein, a simple hydrothermal approach was used to produce well-defined template free m-BiVO₄ dendrites with distinct branches for photo catalytically removal of organic pollutant and photocurrent generation. The development of monoclinic dendrite BiVO₄ was confirmed after comprehensive structural, morphological, and optical examinations. FE-SEM images of m-BiVO₄ revealed transformation of spherical to dendritic morphology with distinct branches by simply changing the HNO₃ to NaOH ratios from 2:1 to 2:2, which are named as BVO 2-1 and BVO 2-2, respectively. The BVO 2-2 dendrites exhibited improved activity of 98% towards methylene blue (MB) photodegradation upon simulated solar light irradiation. The BVO 2-2 dendrites photoelectrode showed an outstanding photocurrent density of 1.4245 mAcm^-2 than that of the BVO 2-1 spherical photoelectrode (0.7367 mAcm^-2). Enhanced photocatalytic and photoelectrochemical action, could be ascribed to the unique morphological changes provides photoactive sites, harvest more light utilization together with higher separation of e^-/h⁺ pairs. Furthermore, photocatalytic mechanism is investigated based on scavenger trapping agent, valence band XPS, UV Visible DRS and PL study. Our findings could pave the way for the development of dendritic nanostructure photocatalysts with improved photocatalytic activity.

Synthesis, characterization, and methylene blue adsorption of multiple-responsive hydrogels loaded with Huangshui polysaccharides, polyvinyl alcohol, and sodium carboxyl methyl cellulose

Huangshui (HS), a typical by-product of traditional Chinese Baijiu, has attracted more and more attention since its rich resources of polysaccharides. However, there's little information on hydrogels preparation by Huangshui polysaccharides (HSPs). A series of novel HSP-loaded hydrogels were synthesized using crude HSP (cHSP), polyvinyl alcohol (PVA), sodium carboxyl methyl cellulose (CMC), and in situ incorporation of Fe₃O₄ for methylene blue (MB) adsorption for the first time. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM) and texture tests indicated the paramagnetic hydrogels with porous structure were formed via physical crosslinking, and cHSP had no effect on hydrogel texture. Notably, cHSP enhanced the swelling capacity and MB adsorption ability of the hydrogels, and the corresponding maximum value was 38.67 g/g and 71.07 mg/g, respectively, when the additive amount of cHSP to the hydrogels was 2 % at 25°С. In addition, the swelling kinetics of hydrogels followed the Schott's second-order kinetics model, while MB adsorption fitted well with the Freundlich isotherm and pseudo-second-order model. Furthermore, intraparticle and film diffusion-controlled MB adsorption process. Significantly, cHSP amount could counteract the negative influence of high temperature on MB adsorption, and the prepared hydrogels could be reusable, demonstrating cHSP effectively promoted the properties of hydrogels and had potential application in MB removal. The adsorption mechanism of MB onto the hydrogels involved ion-exchange, hydrogen bonding, electrostatic interaction, and chemical reaction according to the above results together with the analysis by X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray (EDX) characterizations, thermodynamic, etc.

Emerging bismuth-based direct Z-scheme photocatalyst for the degradation of organic dye and antibiotic residues

Organic dye and antibiotic residues are some of the key substances that can contaminate the environment due to their wide usage in various industries and modern medicine. The degradation of these substances present in waterbodies is essential while contemplating human health. Photocatalysts (PSs) are promising materials that develop highly reactive species instantly by simple solar energy conversion for degrading the organic dye and antibiotic residues and converting them into nontoxic products. Among numerous semiconductors, the bismuth (Bi)-containing PS has received great attention due to its strong sunlight absorption, facile preparation, and high photostability. Owing to the technology advancement and demerits of the traditional methods, a Bi-containing direct Z-scheme PS has been developed for efficient photogenerated charge carrier separation and strong redox proficiency. In this review, a synthetic Bi-based Z-scheme heterojunction that mimics natural photosynthesis is described, and its design, fabrication methods, and applications are comprehensively reviewed. Specifically, the first section briefly explains the role of various semiconductors in the environmental applications and the importance of the Bi-based materials for constructing the Z-scheme photocatalytic systems. In the successive section, overview of Z-scheme PS are concisely discussed. The fourth and fifth sections extensively explain the degradation of the organic dyes and antibiotics utilizing the Bi-based direct Z-scheme heterojunction. Eventually, the conclusions and future perspectives of this emerging research field are addressed. Overall, this review is potentially useful for the researchers involved in the environmental remediation field as a collection of up-to-date research articles for the fabrication of the Bi-containing direct Z-scheme PS.

Zero Discharge of Dyes and Regeneration of a Washing Solution in Membrane-Based Dye Removal by Cold Plasma Treatment

Although dye removal from wastewater streams has been investigated via several approaches using adsorbents, resins, or membranes, it is still hard to avoid the fact that dyes are persistently left in the adsorption materials or washing solutions used to regenerate the used adsorbents. In particular, given that cleaning agents are composed of acid/base, organic solvents, or electrolytes, dye adsorption and adsorbent regeneration processes leave behind more hard-to-manage wastewater containing dyes. In this study, we demonstrated that cold plasma (CP) treatment, which is one of the advanced oxidation processes (AOPs), can be used for zero discharge of dyes and regeneration of a washing solution in a membrane-based dye removal process. Specifically, CP treatment was found to successfully remove dyes released from a washing process to regenerate a used membrane, thereby effectively recycling a cleaning solution. As a result, the regenerated washing solution was more favorable for the adsorbed dyes’ elution, leading to the successful regeneration of a used membrane without a significant loss of dye removal efficiency. This fact was evidenced by a comparative study on the effect of CP treatment on the reusability of membranes and washing solutions and the kinetic analysis of the AOP of the desorbed dyes. We hope that this study contributes to opening a new door for environmentally friendly and sustainable dye removal.

Biochar-based nanocomposite from waste tea leaf for toxic dye removal: From facile fabrication to functional fitness

The present study utilized discarded tea leaf waste to produce 'Tea leaf biochar' (TLB) as the functional matrix for the fabrication of hybrid nanocomposite (nAg-TC), with colloidal deposition of silver nanoparticles (nAg) via modified chemical co-precipitation, for treatment of dye-laden wastewater. The chemical composition, physicochemical properties, and morphology of nAg-TC, and active surface functional groups involved in adsorption were identified using BET, FESEM-EDX, FTIR, TGA, XPS, and XRD. The nAg-TC matrix was found to be heterogeneous, mesoporous, thermostable, with rich in active surface functional groups (-OH, =NH, =CH, CC, CO, CN, and CC), and nAg as a dopant material. The dye adsorption results indicated the maximum removal efficiency (RhB = 95.89%, CR = 94.10%) at 300 K for rhodamine B (RhB) and Congo red (CR) concentrations of 25 mg L^-1 and 22.5 mg L^-1, respectively. The present investigation agreed with Freundlich isotherm (R²_CR:0.991; R²_RhB:0.993) and pseudo-second order kinetic (R²_CR:0.999; R²_RhB:0.999) model, indicating overall adsorption of RhB and CR through spontaneous and exothermic chemisorption on the heterogeneous surface of nAg-TC. The mechanism of RhB and CR adsorption was complex where nAg-TC, possessing the synergistic effects of TLB and nAg, showed surface complexation, electrostatic attraction, and H-bonding, leading to chemisorption. Study showed excellent reusability of spent nAg-TC, and commendable treatment efficiency for dye-laden real industrial effluents. The study exhibits substantial techno-economic feasibility of adsorbent and translates the principles of circular economy into synthesis of value-added products through sustainable management of biowaste and bioresource.