Recent advances for dyes removal using novel adsorbents: A review

Removal of Methylene Blue and Methyl Red from Aqueous Solutions Using Activated Carbons Obtained by Chemical Activation of Caraway Seed

In this study, activated carbons were produced through the chemical activation of caraway seeds using three different activators: Na2CO3, K2CO3, and H3PO4. A 1:2 weight ratio of precursor to activator was maintained in every instance. Comprehensive analyses were conducted on the resultant activated carbons, including elemental analysis, textural parameters determination, Boehm titration for surface oxygen functional groups, pH assessment of aqueous extracts, and quantification of ash content. The produced materials were subjected to adsorption tests for methylene blue and methyl red sodium salt from the liquid phase and the effects of adsorbent dosage, pH of the aqueous dye solution, process temperature, and adsorbent-adsorbate contact time on sorption capacity obtained. To characterize the adsorption model of the examined pollutants, both the Langmuir and Freundlich equations were employed. In addition, the sorption capacity of the obtained carbon materials against an iodine aqueous solution was assessed. The specific surface area of the obtained adsorbents ranged from 269 to 926 m2/g. By employing potassium carbonate to chemically activate the starting substance, the resulting activated carbons show the highest level of specific surface area development and the greatest sorption capacity against the tested impurities-296 mg/g for methylene blue and 208 mg/g for methyl red sodium salt. The adsorption rate for both dyes was determined to align with a pseudo-second-order kinetic model. The experimental adsorption data for methylene blue were well-described by the Langmuir model, whereas the Freundlich model was found to be congruent with the data pertaining to methyl red sodium salt.

Synthesis of a novel porous organic polymer containing triazine and cyclohexanone rings as an efficient methyl red adsorbent from aqueous solutions

In this research, a new porous organic polymer based on triazine and cyclohexanone rings was synthesized via Schiff base condensation, and its performance as an adsorbent for the removal of Methyl Red dye from aqueous solution was investigated. The synthesized polymer was characterized by FT-IR, XRD, SEM, EDS, TEM, TGA, and BET analyses. Five important parameters of pH (4-10), contact time (10-120 min), adsorbent dose (5-10 mg), initial dye concentration (10-70 mg/L), and temperature (25-45 °C) were investigated to optimize the adsorption conditions. Solution pH of 4, contact time of 80 min, adsorbent dose of 8 mg, initial dye concentration of 50 mg/L, and temperature of 45 °C were obtained as the best conditions for the adsorption of methyl red dye. Two widely used Langmuir and Freundlich models were employed to investigate the adsorption isotherm, and the obtained data showed that the adsorption process follows the Langmuir isotherm with a correlation coefficient (R2 = 0.9784) which indicates monolayer adsorption. The achieved maximum adsorption capacity was 178.57 mg/g. Also, the results of kinetic studies indicate that the adsorption process follows the pseudo-second-order kinetic, which suggests that chemical interactions play an important role in dye removal. Furthermore, the results showed that the adsorption process of methyl red dye by polymer is endothermic.

Synthesis of a pyridine-based covalent organic framework as an efficient adsorbent for rhodamine B removal

Covalent organic frameworks (COFs), featured with crystalline structures, permanent porosity, and designable organic skeletons, are good candidates for serving as adsorbents. Herein, a new pyridine-based two-dimensional COF (TAPP-DBTA-COF) was constructed via the condensation of 2,4,6-tris(4-aminophenyl)pyridine and 2,5-dibromobenzene-1,4-dicarbaldehyde. TAPP-DBTA-COF displayed high-performance for the removal of rhodamine B (Rh B) from water with high capacity, good adaptability and reusability. The maximum adsorption capacity for Rh B can reach up to 1254 mg g-1, and the kinetic constant was determined as k2 = 0.00244 g mg-1 min-1. Moreover, the corresponding amorphous polymer of TAPP-DBTA-COF, termed as TAPP-DBTA-COP, was synthesized from the same starting materials. The lower efficiency of TAPP-DBTA-COP in capture of Rh B revealed that the ordered pore structure, large specific surface area and rich adsorption sites play an important role in adsorption.

Treatment of textile wastewater using carbon-based nanomaterials as adsorbents: a review

Waste derived from the textile industry can contain a wide variety of pollutants of organic and inorganic natures, such as dyes (e.g., acid, basic, reactive, mordant dyes) and toxic metals (e.g., lead, chromium, cadmium). The presence of pollutants at high concentrations in textile waste makes them relevant sources of pollution in the environment. To solve this problem, various technologies have been developed for the removal of pollutants from these matrices. Thus, adsorption emerges as an efficient alternative for textile waste remediation, providing advantages as simplicity of operation, economy, possibility of using different adsorbent materials, and developing on-line systems that allow the reuse of the adsorbent during several adsorption/desorption cycles. This review will initially propose an introduction to the adsorption world, its fundamentals, and aspects related to kinetics, equilibrium, and thermodynamics. The possible mechanisms through which a pollutant can be retained on an adsorbent will be explained. The analytical techniques that offer valuable information to characterize the solid phases as well as each adsorbate/adsorbent system will be also commented. The most common synthesis techniques to obtain carbon nano-adsorbents have been also presented. In addition, the latest advances about the use of these adsorbents for the removal of pollutants from textile waste will be presented and discussed. The contributions reported in this manuscript demonstrated the use of highly efficient carbon-based nano-adsorbents for the removal of both organic and inorganic pollutants, reaching removal percentages from 65 to 100%.

e-Beam and γ-rays Induced Synthesis and Catalytic Properties of Copper Nanoclusters-Deposited Composite Track-Etched Membranes

Effective removal of toxic inorganic and organic pollutants is one of the current leading challenges of wastewater treatment. In this study, the decomposition of methylene blue (MB) under UV light irradiation was investigated in the presence of copper nanoclusters (NCs)-deposited polyethylene terephthalate (PET) track-etched hybrid membranes. PET track-etched membranes (TeMs) with an average pore size of ~400 nm were grafted by functional acrylic acid (AA) monomer under electron beam irradiation after oxidation with H₂O₂/UV system. The radiation dose varied between 46 and 200 kGy. For the deposition of copper NCs, poly(acrylic acid) (PAA)-grafted membranes saturated with Cu(II) ions were irradiated either by electron beam or γ-rays to obtain copper-based NCs for the catalytic degradation of MB. Irradiation to 100 kGy with accelerated electrons resulted in the formation of small and uniform copper hydroxide (Cu(OH)₂) nanoparticles homogeneously distributed over the entire volume of the template. On the other hand, irradiation under γ-rays yielded composites with copper NCs with a high degree of crystallinity. However, the size of the deposited NCs obtained by γ-irradiation was not uniform. Nanoparticles with the highest uniformity were obtained at 150 kGy dose. Detailed analysis by X-ray diffraction (XRD) and scanning electron microscopy (SEM) confirmed the loading of copper nanoparticles with an average size of 100 nm on the inner walls of nanochannels and on the surface of PET TeMs. Under UV light irradiation, composite membranes loaded with NCs exhibited high photocatalytic activity. It was determined that the highest catalytic activity was observed in the presence of Cu(OH)₂@PET-g-PAA membrane obtained at 250 kGy. More than 91.9% of the initial dye was degraded when this hybrid membrane was employed for 180 min, while only 83.9% of MB was degraded under UV light using Cu@PET-g-PAA membrane. Cu(OH)₂@PET-g-PAA membranes obtained under electron beam irradiation demonstrated a higher photocatalytic activity compared to Cu@PET-g-PAA membranes attained by γ-rays.

Cationic dialdehyde cellulose microfibers for efficient removal of eriochrome black T from aqueous solution

Materials based on cellulose have been widely used as a decontaminant agent of wastewater. However, it can not be found in the literature any application of the cationic dialdehyde cellulose (cDAC) in anionic dye removal. Therefore, this study aims a circular economy concept using sugarcane bagasse to obtain a functionalized cellulose by oxidation and cationization. cDAC was characterized by SEM, FT-IR, oxidation degree, and DSC. Adsorption capacity was evaluated by pH, kinetic, concentration effect, strength ionic tests, and recycling. The kinetic followed Elovich model (R² = 0.92605 for EBT = 100 mg/L) and non-linear Langmuir model (R² = 0.94542), which resulted in a maximum adsorption capacity of 563.30 mg/g. The cellulose adsorbent reached an efficient recyclability of 4 cycles. Thus, this work presents a potential material to become a new, clean, low-cost, recyclable, and environmentally friendly alternative for effluent decontamination-containing dyes.

Efficient removal of methylene blue from water using magnetic Alyssum homolocarpum seed gum-based matrix

In this study, we fabricated magnetic Fe3O4 nanoparticles conjugated with anionic hydroxypropyl starch-graft-acrylic acid (Fe3O4@AHSG) for the efficient removal of methylene blue (MB) dye from aqueous solutions. The synthesized nanoconjugates were characterized using various techniques. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) analysis revealed that the particles exhibited homogeneously distributed nanosized spherical shapes with a mean diameter of 41.72 ± 6.81 nm. The EDX analysis confirmed the absence of impurities, with the Fe3O4 particles comprising 64.76 % iron and 35.24 % atomic oxygen. Dynamic light scattering (DLS) measurements showed a monodisperse particle system with a mean hydrodynamic size of 135.4 nm (polydispersity index, PI = 0.530) for the Fe3O4 nanoparticles and 163.6 nm (PI = 0.498) for the Fe3O4@AHSG adsorbent. Vibrating sample magnetometer (VSM) analysis indicated superparamagnetic behavior for both Fe3O4 and Fe3O4@AHSG, with higher saturation magnetization (Ms) observed for Fe3O4. The dye adsorption studies demonstrated that the adsorbed dye capacity increased with increasing initial MB concentration and adsorbent dose. The pH of the dye solution significantly influenced the adsorption, with the highest adsorption observed at basic pH values. The presence of NaCl reduced the adsorption capacity due to increased ionic strength. Thermodynamic analysis indicated the thermodynamically favorable and spontaneous nature of the adsorption process. Kinetic studies revealed that the pseudo-second-order model provided the best fit to the experimental data, suggesting chemisorption as the rate-limiting step. Overall, Fe3O4@AHSG nanoconjugates exhibited excellent adsorption capacity and could be a promising material for effective removal of MB dye from wastewater.

Electrospun Fe doped TiO2 fiber photocatalyst for efficient wastewater treatment

Water pollution caused by industrial wastewater is the most critical environmental problem in the world. Synthetic dyes are commonly used in various industries such as paper, plastic, printing, leather and textile for their ability to impact color. Complex composition, high toxicity and low biodegradability of dyes make them difficult to degrade which causes a substantial negative impact on overall ecosystems. To address this issue we synthesized TiO₂ fibers photocatalyst using the combination of sol-gel and electrospinning techniques to be used in the degradation of dyes which causes water pollution. We doped Fe in TiO₂ fibers to enhance the absorption in the visible region of the solar spectrum which will also help to increase the degradation efficiency. As synthesized pristine TiO₂ fibers and Fe doped TiO₂ fibers were analyzed using different characterization techniques such as X-ray diffraction, Scanning electron microscopy, Transmission electron microscopy, UV-Visible spectroscopy, X-ray photoelectron spectroscopy. 5% Fe doped TiO₂ fibers show excellent photocatalytic degradation activity for rhodamine B (99% degradation in 120 min). It can be utilized for degradation of other dye pollutants such as methylene blue, Congo red and methyl orange. It shows good photocatalytic activity (97%) even after 5 cycles of reuse. The radical trapping experiments reveals that holes, ^•O₂^- and ^•OH has a significant contribution in the photocatalytic degradation. Due to the robust fibrous nature of 5FeTOF the process of collection of photocatalysts was simple and without loss as compared to powder photocatalysts. This justifies our selection of electrospinning method of synthesis of 5FeTOF which is also useful for large scale production.

Green Synthesis of the Effectively Environmentally Safe Metakaolin-Based Geopolymer for the Removal of Hazardous Industrial Wastes Using Two Different Methods

Untreated wastewater pollution causes environmental degradation, health issues, and ecosystem disruption. Geopolymers offer sustainable, eco-friendly alternatives to traditional cement-based materials for wastewater solidification and removal. In this study, we investigate how wastewater containing organic and inorganic pollutants can be removed using geopolymer mixes based on metakaolin incorporation with cement kiln dust as an eco-friendly material. The present investigation compares the efficacy of two different techniques (solidification and adsorption) for reducing dye contaminants and heavy metals from wastewater using a geopolymer based on metakaolin incorporation with cement kiln dust. This study investigated the adsorption capacity of a geopolymer based on metakaolin incorporating two different ratios (20% and 40% by weight) of cement kiln dust (MC1 and MC2) for the reactive black 5 dyeing bath effluent (RBD) only and in a combination of 1200 mg/L of Pb²⁺ and Cd²⁺, each separately, in aqueous solutions under different adsorption parameters. The results of the adsorption technique for the two prepared geopolymer mixes, MC1 and MC2, show that MC1 has a higher adsorption activity than MC2 toward the reactive black 5 dyeing bath effluent both alone and in combination with Pb²⁺ and Cd²⁺ ions separately. The study also looked at using MC1 mix to stabilize and solidify both the dyeing bath effluent alone and its combination with 1200 mg/L of each heavy metal individually inside the geopolymer matrix for different time intervals up to 60 days of water curing at room temperature. The geopolymer matrix formed during the process was analyzed using FTIR, SEM, and XRD techniques to examine the phases of hydration products formed. The results showed that MC1 effectively adsorbs, stabilizes, and solidifies the dying bath effluent for up to 60 days, even with high heavy metal concentrations. On the other hand, geopolymer mixes showed an increase in mechanical properties when hydration time was increased to 60 days. According to our findings, the type of geopolymer developed from metakaolin and 20 wt.% cement kiln dust has the potential to be employed in the treatment of wastewater because it has good adsorption and solidification activity for the reactive black 5 dye effluent alone and for a mixture of dye pollutants with both Pb²⁺ and Cd²⁺ ions separately. Our results have significant implications for wastewater treatment and environmental remediation efforts, as they offer a sustainable solution for managing hazardous waste materials.

Augmented dye eradication from wastewater using alkali-aided, reinforced waste acacia (Acacia auriculiformis) leaves

The present investigation demonstrates the augmented dye scavenging from wastewater using alkali-mutated acacia (Acacia auriculiformis) leaves powder. The material was synthesized by mild chemical activation by using 0.1 M sodium hydroxide as an activator under room temperature stirring for 3h and isolated as a dark brown powder. The material was characterized using FTIR, FESEM, XRD, and pHzpc; and tested successfully with crystal violet and methylene blue. While FTIR confirms the presence of polyphenolic and polysaccharide moieties, FESEM reveals unprecedented circular hollow pipe-like channels decorated in a highly ordered fashion, facing pores for optimum dye uptake. The adsorption is tunable with working pH, and the maximum adsorption capacities are 67.25 and 78.55 mg g-1 for CV and MB. Both adsorption process follows Langmuir isotherm (R2 = 0.994) and pseudo-2nd-order kinetics (R2 = 0.999). Thermodynamic analysis verifies a spontaneous process with an endothermic interaction beside an elevated degree of randomness. About 80% of the spent material could be regenerated using 1:1 methanol/water. Analysis of industrial effluent suggests 37% removal per cycle, with an operating ceiling of 95%. To wind up, due to huge availability, porous nature, and superior adsorption capacity over other phytosorbents, NaOH-activated acacia leaves could be considered as techno-economic and potential scavengers for sustainable water treatment.

Exploring the Potential of Fique Fiber as a Natural Composite Material: A Comprehensive Characterization Study

Many studies available in the literature focus mainly on the mechanical characterization of fiber, leaving out other physicochemical and thermogravimetric analyses that allow for establishing its potential as an engineering material. This study characterizes fique fiber for its potential use as an engineering material. The fiber's chemical composition and physical, thermal, mechanical, and textile properties were analyzed. The fiber has a high holocellulose content and low lignin and pectin content, indicating its potential as a natural composite material for various applications. Infrared spectrum analysis revealed characteristic bands associated with multiple functional groups. The fiber had monofilaments with diameters around 10 μm and 200 μm, as determined by AFM and SEM images, respectively. Mechanical testing showed the fiber could resist a maximum stress of 355.07 MPa, with an average maximum strain at which breakage occurs of 8.7%. The textile characterization revealed a linear density range of 16.34 to 38.83 tex, with an average value of 25.54 tex and a regain of 13.67%. Thermal analysis showed that the fiber's weight decreased by around 5% due to moisture removal in the range of 40 °C to 100 °C, followed by weight loss due to thermal degradation of hemicellulose and glycosidic linkages of cellulose ranging from 250 to 320 °C. These characteristics suggest that fique fiber can be used in industries such as packaging, construction, composites, and automotive, among others.

Superior performance of novel chitosan-based flocculants in decolorization of anionic dyes: Responses of flocculation performance to flocculant molecular structures and hydrophobicity and flocculation mechanism

To achieve economical and efficient decolorization, two novel flocculants, weakly hydrophobic comb-like chitosan-graft-poly (N, N-Dimethylacrylamide) (CSPD) and strongly hydrophobic chain-like chitosan-graft-L-Cyclohexylglycine (CSLC) were synthesized in this study. To assess the effectiveness and application of CSPD and CSLC, the impacts of factors, including flocculant dosages, initial pH, initial dye concentrations, co-existing inorganic ions and turbidities, on the decolorization performance were explored. The results suggested that the optimum decolorizing efficiencies of the five anionic dyes ranged from 83.17% to 99.40%. Moreover, for accurately controlling flocculation performance, the responses to flocculant molecular structures and hydrophobicity in flocculation using CSPD and CSLC were studied. The Comb-like structure gives CSPD a wider dosage range for effective decolorization and better efficiencies with large molecule dyes under weak alkaline conditions. The strong hydrophobicity makes CSLC more effective in decolorization and more suitable for removing small molecule dyes under weak alkaline conditions. Meanwhile, the responses of removal efficiency and floc size to flocculant hydrophobicity are more sensitive. Mechanism studies revealed that charge neutralization, hydrogen bonding and hydrophobic association worked together in the decolorization of CSPD and CSLC. This study has provided meaningful guidance for developing flocculants in the treatment of diverse printing and dyeing wastewater.

Three-dimensional lignin-based polyporous carbon@polypyrrole for efficient removal of reactive blue 19: A synergistic effect of the N and O groups

Reactive blue 19 is one of the abundant carcinogens commonly used in industrial applications. This study transformed industrial lignin into a lignin-based polyporous carbon@polypyrrole (LPC@PPy) by a hydrothermal-activation-in situ polymerization strategy for removal of reactive blue 19. The hydrothermal reaction and polypyrrole polymerization provide abundant O and N groups, and the pore-making process promotes the even distribution of O and N groups in the 3D pore of LPC@PPy, which is favorable for the adsorption of reactive blue 19. The adsorption capacity of LPC@PPy for reactive blue 19 is 537.52 mg g-1, which is 2.04 times the performance of LPC (only hydrothermal and activation process, only have O groups) and 3.36 times that of LC (direct lignin activation, lack of O and N groups). After 8 cycles, LPC@PPy still maintained a high adsorption capacity of 92.14 % for reactive blue 19. In addition, this study found that N and O groups in the material played an important role in adsorption, mainly pyridinic-N, C-OH, -COOR, -C-O- and CC. This work provides a new strategy for the removal of reactive blue 19 and determines the groups that mainly interact with reactive blue 19, which provides a new reference for adsorption, catalysis and related fields.

Decolorization of multicomponent dye-laden wastewater by modified waste fly ash: a parametric analysis for an anionic and cationic combination of dyes

In this research study, waste fly ash (WFA) underwent acid activation and subsequent amine functionalization using ammonia solution. This treatment improves the porosity, thermal tendency and crystallinity of WFA. Modified WFA was tested under different experimental conditions to treat the wastewater consisting of different concentrations of cationic (methylene blue and rhodamine 6G) and anionic (methyl orange) dyes. As an individual, methylene blue (MB) and rhodamine 6G (Rh) showed ~ 100% and ~ 82% removal efficiencies respectively in an alkaline medium while methyl orange (MO) exhibited only ~ 20% adsorption in the same medium. An antagonistic effect was observed in adsorption when wastewater contains both cationic dyes whereas the combination of cationic and anionic dyes in solution manifested a synergistic effect. For all individual and binary dye combinations, there is a close agreement in observed and calculated uptakes when the data was fitted to the fractional order kinetic rate equation. The adsorption of all dyes is spontaneous and endothermic in nature except for MB/MO combination where the process is exothermic in nature. 24.93 mg/g, 24.83 mg/g, and 14.95 mg/g monolayer uptake capacities of MB, Rh, and MO were found respectively from isothermal analysis of single dye adsorption data. Further, extended sips model gave higher correlation coefficient (R² = 0.99) and addressed the failed assumptions of both the Langmuir and Freundlich models. Overall, in the experimental results, the modified waste fly ash could act as successful adsorbent to treat dye bearing wastewater.

Flax fiber based semicarbazide biosorbent for removal of Cr(VI) and Alizarin Red S dye from wastewater

In the present study, flax fiber based semicarbazide biosorbent was prepared in two successive steps. In the first step, flax fibers were oxidized using potassium periodate (KIO4) to yield diadehyde cellulose (DAC). Dialdehyde cellulose was, then, refluxed with semicarbazide.HCl to produce the semicarbazide functionalized dialdehyde cellulose (DAC@SC). The prepared DAC@SC biosorbent was characterized using Brunauer, Emmett and Teller (BET) and N2 adsorption isotherm, point of zero charge (pHPZC), elemental analysis (C:H:N), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analyses. The DAC@SC biosorbent was applied for the removal of the hexavalent chromium (Cr(VI)) ions and the alizarin red S (ARS) anionic dye (individually and in mixture). Experimental variables such as temperature, pH, and concentrations were optimized in detail. The monolayer adsorption capacities from the Langmuir isotherm model were 97.4 mg/g and 18.84 for Cr(VI) and ARS, respectively. The adsorption kinetics of DAC@SC indicated that the adsorption process fit PSO kinetic model. The obtained negative values of ΔG and ΔH indicated that the adsorption of Cr(VI) and ARS onto DAC@SC is a spontaneous and exothermic process. The DAC@SC biocomposite was successfully applied for the removal of Cr(VI) and ARS from synthetic effluents and real wastewater samples with a recovery (R, %) more than 90%. The prepared DAC@SC was regenerated using 0.1 M K2CO3 eluent. The plausible adsorption mechanism of Cr(VI) and ARS onto the surface of DAC@SC biocomposite was elucidated.

Efficient removal of methylene blue from aqueous solution by ZIF-8-decorated helicoidal electrospun polymer strips

Immobilization of metal-organic frameworks (MOFs) on electrospun products for wastewater treatment has garnered considerable attention in recent years. However, the effect of the overall geometry and surface-area-to-volume ratio of MOF-decorated electrospun architectures on their performances have rarely been investigated. Herein, we prepared polycaprolactone (PCL)/polyvinylpyrrolidone (PVP) strips with helicoidal geometries via immersion electrospinning. By regulating the weight ratio of PCL to PVP, the morphologies and surface-area-to-volume ratios of the PCL/PVP strips could be controlled precisely. Then, the zeolitic imidazolate framework-8 (ZIF-8) for removing methylene blue (MB) from an aqueous solution was immobilized on the electrospun strips, resulting in ZIF-8-decorated PCL/PVP strips. The key characteristics of these composite products, such as adsorption and photocatalytic degradation behavior toward MB in the aqueous solution, were carefully investigated. Owing to the desired overall geometry and high surface-area-to-volume ratio of the ZIF-8-decorated helicoidal strips, a high MB adsorption capacity of 151.6 mg g^-1 was obtained, which is significantly higher than those with conventional electrospun straight fibers. In addition, higher MB uptake rates, higher recycling and kinetic adsorption efficiencies, higher MB photocatalytic degradation efficiencies, and faster MB photocatalytic degradation rates were confirmed. This work provides new insights to improve the performance of existing and potential electrospun product-based water treatment strategies.

Removal of Methylene Blue from Aqueous Solutions by Surface Modified Talc

In this study, raw talc powder surface modification was conducted, and the powder was modified in two different methods using acid washing and ball milling. Modified talc was characterized by X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). In order to investigate the adsorption capacity of modified talc on dyes, adsorption experiments were carried out with methylene blue (MB) in aqueous solutions as the target contaminant. The findings of the characterization revealed that both modifications increased the adsorption capacity of talc, which was attributed to changes in specific surface area and active groups. The influence of process parameters such as contact time, pH, dye concentration, and adsorbent dosage on the adsorption performance was systematically investigated. Modified talc was able to adsorb MB rapidly, reaching equilibrium within 60 min. Additionally, the adsorption performance was improved as the pH of the dye solution increased. The isotherms for MB adsorption by modified talc fitted well with the Langmuir model. The pseudo-second-order model in the adsorption kinetic model properly described the adsorption behavior. The results show that the modified talc can be used as an inexpensive and abundant candidate material for the adsorption of dyes in industrial wastewater.

Magnetite carboxymethylcellulose as biological macromolecule-based absorbent for cationic dyes removal from environmental samples

In this study, magnetite carboxymethylcellulose (CMC@Fe₃O₄) composite as magnetic biological molecules were synthetized for the use as adsorbent to remove four types of cationic dyes, namely Methylene Blue, Rhodamine B, Malachite Green, and Methyl Violet from aqueous solution. The characteristic of the adsorbent was achieved by Fourier Transform Infrared Spectroscopy, Field Emission Scanning Electron Microscope (FESEM), X-ray Diffraction, Vibrating Sample Magnetometer and Thermal Gravimetric Analysis techniques. Besides, essential influencing parameters of dye adsorption; the solution pH, solution temperature, contact time, adsorbent concentration and initial dye dosage were studied. FESEM analysis showed the magnetic Fe₃O₄-TB, Fe₃O₄@SiO₂, Fe₃O₄@SiO₂-NH₂ and CMC@Fe₃O₄ composites were in spherical shape, with average size of 43.0 nm, 92.5 nm, 134.0 nm and 207.5 nm, respectively. On the saturation magnetization (Ms), the results obtained were 55.931 emu/g, 34.557 emu/g, 33.236 emu/g and 11.884 emu/g. From the sorption modelling of Isotherms, Kinetics, and Thermodynamics, the adsorption capacity of dyes is (MB = 103.33 mg/g), (RB = 109.60 mg/g), (MG = 100.08 mg/g) and (MV = 107.78 mg/g). With all the adsorption processes exhibited as exothermic reactions. The regeneration and reusability of the synthetized biological molecules-based adsorbent was also assessed.

Non-toxic chitosan-pyrazole adsorbent enriched with greenly synthesized zinc oxide nanoparticles for dye removal from wastewater

The limited usage of chitosan as a dye adsorbent is attributed to its compact structure and low swelling ability, despite its exceptional properties. The present study aimed to prepare novel chitosan/pyrazole Schiff base (ChS) adsorbents enriched with greenly synthesized zinc oxide nanoparticles. The preparation of ZnO-NPs was carried out through a green approach using the Coriandrum sativum extract. The presence of ZnO-NPs at the nanoscale was validated through TEM, DLS and XRD analyses. FTIR, ¹H NMR confirmed the successful preparation of the Schiff base and its ZnO-NPs adsorbents. The incorporation of ZnO-NPs improved the thermal, swelling and antimicrobial properties of the chitosan Schiff base. In addition, a significant improvement in the adsorption of Maxilon Blue dye from its aqueous solution by the Schiff base/ZnO-NPs adsorbent. The prepared ChS/ZnO-NPs adsorbent has the potential to be used as an alternative to conventional adsorbents for the removal of dyes from wastewater.

Adsorption Kinetics of Methyl Orange from Model Polluted Water onto N-Doped Activated Carbons Prepared from N-Containing Polymers

This study aimed to assess the role of polymeric sources (polypyrrole, polyaniline, and their copolymer) of nitrogen (N)-doped activated carbons (indexed as PAnAC, PPyAC, and PnyAC, respectively) on their adsorption efficiency to remove methyl orange (MO) as a model cationic dye. The adsorbents were characterized using FTIR, SEM, TGA, elemental analysis, and surface area. The kinetic experiments were performed in batches at different MO concentrations (C₀) and adsorbent dosages. The adsorption kinetic profiles of pseudo-first-order, pseudo-second-order (PSO), Elovich, intraparticle diffusion, and liquid film diffusion models were compared. The results showed a better fit to the PSO model, suggesting a chemisorption process. The adsorption capacity (q_e, mg/g) was found to have increased as MO C₀ increased, yet decreased as the adsorbent quantity increased. At the adsorption operating condition, including MO C₀ (200 ppm) and adsorbent dose (40 mg), the calculated q_e values were in the order of PAnAC (405 mg/g) > PPyAC (204 mg/g) > PnyAC (182 mg/g). This trend proved the carbon precursor's importance in the final properties of the intended carbons; elemental analysis confirmed that the more nitrogen atoms are in the activated carbon, the greater the number of active sites in the adsorbent for accommodating adsorbates. The diffusion mechanism also assumed a rate-limiting step controlled by the film and intraparticle diffusion. Therefore, such an efficient performance may support the target route's usefulness in converting nitrogenous-species waste into valuable materials.

Removal of chromium (VI) from aqueous environments using composites of polyaniline-cherry leaves

Composites of Polyaniline (PANI)-prune, peach, cherry, grape, fig and walnut leaves were synthesized under various conditions and were used to remove chromium (VI) from aqueous environments in discontinuous experiments. The results showed that the highest percentage of Cr (VI) removal (40.3%) belonged to the composite consisting of cherry leaves and PANI. Synthesis conditions of this composite were then studied to increase Cr (VI) removal. The results of the experiment on the various solvents are used in the synthesis of the composite of PANI-cherry leaves indicated that the best solvent (with 40.93% Crn(VI) removal) was water. The effects of polyvinyl alcohol (PVA) and polyethylene glycol (PEG) as additives on the synthesis of the composite PANI-cherry leaves were studied and it was revealed that the best-synthesized composite (with 51.64% Cr removal) was produced in presence of PVA (2 g/L), and the optimum pH and contact time were 2 and 30 min, respectively. Moreover, the adsorption process followed Langmuir and Freundlich adsorption isotherms, and the maximum Cr adsorption capacity was 33.01 mg/g. The results of the FTIR and XRD tests and SEM images for this composite were studied. The SEM images demonstrated that the addition of PVA reduced the size of the particles and made them more uniform. The XRD test indicated that the synthesized composite was amorphous, and the FTIR test confirmed the synthesis of the composite.

Challenges associated with cellulose composite material: Facet engineering and prospective

Cellulose is the most abundant polysaccharide on earth. It has a large number of desirable properties. Its low toxicity makes it more useful for a variety of applications. Nowadays, its composites are used in most engineering fields. Composite consists of a polymer matrix and use as a reinforcing material. By reducing the cost of traditional fibers, it has an increasing demand for environment-friendly purposes. The use of these types of composites is inherent in moisture absorption with hindered natural fibers. This determines the reduction of polymer composite material. By appropriate chemical surface treatment of cellulose composite materials, the effect could be diminished. The most modern and advanced techniques and methods for the preparation of cellulose and polymer composites are discussed here. Cellulosic composites show a reinforcing effect on the polymer matrix as pointed out by mechanical characterization. Researchers tried their hard work to study different ways of converting various agricultural by-products into useful eco-friendly polymer composites for sustainable production. Cellulose plays building blocks, that are critical for polymer products and their engineering applications. The most common method used to prepare composites is in-situ polymerization. This help to increase the yields of cellulosic composites with a significant enhancement in thermal stability and mechanical properties. Recently, cellulose composites used as enhancing the incorporation of inorganic materials in multi-functional properties. Furthermore, we have summarized in this review the potential applications of cellulose composites in different fields like packaging, aerogels, hydrogels, and fibers.

Synthesis of innovative and sustainable gelatin@graphene oxide-crosslinked-zirconium silicate@gelatin nanobiosorbent for effective biosorption of basic fuchsin dye

Most dye stuffs and coloring materials are mainly categorized as hazardous pollutants in water effluents due to their nature as non-biodegradable, highly toxic and extremely carcinogenic. For this reason, rapid and efficient eradication of waste dyes from wastewaters before discharging into water streams must be accomplished by an acceptable approach as adsorption technique. Therefore, the present study is aimed and devoted to synthesize a novel nanobiosorbent from three different constituents, gelatin (Gel) as a sustainable natural product, graphene oxide (GO) as an example of highly stable carbonaceous material and zirconium silicate (ZrSiO₄) as an example of combined metal oxides for the formation of Gel@GO-F-ZrSiO₄@Gel by using formaldehyde (F) as a cross-linkage reagent. Several characterization techniques as FT-IR were employed to identify the incorporated surface reactive Functionalities in Gel@GO-F-ZrSiO₄@Gel as -OH, =NH, -NH₂, -COOH and C=O, etc. The morphology for particle shape and size of Gel@GO-F-ZrSiO₄@Gel were confirmed from the SEM and TEM analyses providing 15.75- 32.79 nm. The surface area was determined by the BET and found to correspond to 219.46 m² g^-1. Biosorptive removal of basic fuchsin (BF) pollutant as an example of a widely applicable dye in various activities was monitored and optimized under the influence of pH (2-10), reaction time (1-30 min), initial BF pollutant concentration (5-100 mg L^-1), nanobiosorbent dosage (5-60 mg), temperature (30-60 °C) and interfering ions. The maximum biosorptive removal values of BF dye were established as 96.0 and 95.2% using 5 and 10 mg L^-1, respectively at the recommended pH 7 condition. The Thermodynamic parameters demonstrated that the BF dye adsorption onto Gel@GO-F-ZrSiO₄@Gel was taken place via spontaneous and endothermic reaction. Chemisorption is the predominant adsorption mechanism by forming multilayers upon nonhomogeneous surface in accordance with Freundlich model hypothesis. The applicability of the optimized Gel@GO-F-ZrSiO₄@Gel in biosorptive removal of BF pollutant from real water sample was successfully accomplished by the batch technique. Thus, this study clearly shows that Gel@GO-F-ZrSiO₄@Gel exhibited significant influences on remediation of industrial effluents containing BF pollutant with superior efficiency.

Recent advances in nanomaterials based sustainable approaches for mitigation of emerging organic pollutants

Emerging organic pollutants (EOPs) are a category of pollutants that are relatively new to the environment and recently garnered a lot of attention. The majority of EOPs includes endocrine-disrupting chemicals (EDCs), antibiotic resistance genes (ARGs), pesticides, dyes and pharmaceutical and personal care products (PPCPs). Exposure to contaminated water has been linked to an increase in incidences of malnutrition, intrauterine growth retardation, respiratory illnesses, liver malfunctions, eye and skin diseases, and fatalities. Consequently, there is a critical need for wastewater remediation technologies which are effective, reliable, and economical. Conventional wastewater treatment methods have several shortcomings that can be addressed with the help of nanotechnology. Unique characteristics of nanomaterials (NMs) make them intriguing and efficient alternative in wastewater treatment strategies. This review emphasis on the occurrence of divers emerging organic pollutants (EOPs) in water and their effective elimination via different NMs based methods with in-depth mechanisms. Furthermore, it also delves the toxicity assessment of NMs and critical challenges, which are crucial steps for practical implementations.

An Investigation of a Natural Biosorbent for Removing Methylene Blue Dye from Aqueous Solution

T he current study reports the use of zeolite prepared from a kaolin composite via physical mixing with different ratios from fiber of palm tree (Zeo-FPT) as a sustainable solid sorbent for the removal of methylene blue (MB) dye from aqueous solutions. The prepared biosorbent was fully characterized using XRD, TGA, SEM, and FTIR. The impacts of various analytical parameters, for example, contact time, dosage, MB dye concentration, and the pH of the solution, on the dye adsorption process were determined. After a contact time of 40 min, the capacity to remove MB dye was 0.438 mg g−1 at a Zeo-FPT composition ratio of 1F:1Z. At pH 8, Zeo-FPT (1F:1Z) had a removal efficiency of 87% at a sorbent dosage of 0.5 g for a concentration of MB dye in an aqueous phase of 10 mg L−1. The experimental data were also analyzed using the kinetic and adsorption isotherm models. The retention process fitted well with the pseudo-second-order model (R2 0.998), where the Qe,calc of 0.353 mg g−1 was in acceptable agreement with the Qe,exp of 0.438 mg g−1. The data also fitted well with the Freundlich isotherm model, as indicated by the correlation coefficient value (R2 0.969). The Zeo-FPT attained a high percentage (99%) in the removal of MB dye from environmental water samples (tap water, bottled water, and well water). Thus, it can be concluded that the proposed zeolite composite with fiber of palm tree (Zeo-FPT) is a suitable, environmentally friendly, and low-cost adsorbent for removing dyes from wastewater.

Development of a ZnOS+C Composite as a Potential Adsorbent for the Effective Removal of Fast Green Dye from Real Wastewater

Wastewater treatment is becoming increasingly important due to the potential shortage of pure drinking water in many parts of the world. Adsorption offers a potential technique for the uptake of contaminants and wastewater purification. In the last two decades, several efforts have been made to remove fast green (FG) dye from wastewater via different adsorbent materials. However, adsorption capacity shown by these adsorbents is low and time-consuming. Herein, we have synthesized for the first time a new powdered adsorbent ZnOS+C, modified zinc peroxide with sulfur and activated carbon to effectively remove FG dye from wastewater. Results of batch adsorption experiments have suggested that ZnOS+C has the maximum adsorption potential of 238.28 mg/g for FG dye within 120 min of adsorption equilibrium for a wide range of pH ranging from 2 to 10 pH. The adsorption process conforms to the Freundlich isotherm model, suggesting a multilayered adsorption process on the outer surface of ZnOS+C. The adsorption kinetics study indicates that the kinetics of the reaction are the intraparticle diffusion model. Briefly, this study shows proof of the application of ZnOS+C powder as a new eco-friendly adsorbent with extremely high efficiency and high surface area for removing FG dye.

Understanding the intermediates and carbon dioxide adsorption of potassium chloride-incorporated graphitic carbon nitride with tailoring melamine and urea as precursors

In this study, we demonstrated the synthesis of potassium chloride (KCl)-incorporated graphitic carbon nitride, (g-C₃N₄, CN) with varying amounts of N-vacancies and pyridinic-N as well as enhanced Lewis basicity, via a single-step thermal polymerization by tailoring the precursors of melamine and urea for carbon oxide (CO₂) capture. Melamine, as a precursor, undergoes a phase transformation into melam and triazine-rich g-C₃N₄, whereas the addition of urea polymerizes the mixture to form melem and heptazine-rich g-C₃N₄ (CN11). Owing to the abundance of pyridinic-N and the high surface area, CN11 adsorbed higher amounts of CO₂ (44.52 μmol m^-2 at 25 °C and 1 bar of CO₂) than those reported for other template-free carbon materials. Spectroscopic analysis revealed that the enhanced CO₂ adsorption is due to the presence of pyridinic-N and Lewis basic sites on the surface. The intermediates of CO₂adsorption, including carbonate and bicarbonate species, attached to the CN samples were identified using in-situ Fourier-transform infrared spectroscopy (FTIR). This work provides insights into the mechanism of CO₂ adsorption by comparing the structural features of the synthesized KCl-incorporated g-C₃N₄ samples_. CN11, with an excellent CO₂ uptake capacity, is viewed as a promising candidate for CO₂ capture and storage.

Nitrogen-Rich Polyaniline-Based Activated Carbon for Water Treatment: Adsorption Kinetics of Anionic Dye Methyl Orange

In the present work, a nitrogen-rich activated carbon (PAnAC) was prepared using polyaniline (PAn) as a precursor to represent one possible conversion of nitrogen-containing polymeric waste into a valuable adsorbent. PAnAC was fabricated under the chemical activation of KOH and a PAn precursor (in a 4:1 ratio) at 650 °C and was characterized using FTIR, SEM, BET, TGA, and CHN elemental composition. The structural characteristics support its applicability as an adsorbent material. The adsorption performance was assessed in terms of adsorption kinetics for contact time (0-180 min), methyl orange (MO) concentration (C₀ = 50, 100, and 200 ppm), and adsorbent dosages (20, 40, and 80 mg per 250 mL batch). The kinetic results revealed a better fit to a pseudo-second-order, specifically nonlinear equation compared to pseudo-first-order and Elovich equations, which suggests multilayer coverage and a chemical sorption process. The adsorption capacity (q_e) was optimal (405.6 mg/g) at MO C₀ with PAnAC dosages of 200 ppm and 40 mg and increased as MO C₀ increased but decreased as the adsorbent dosage increased. The adsorption mechanism assumes that chemisorption and the rate-controlling step are governed by mass transfer and intraparticle diffusion processes.

Regulating the assembly and expansion of the silver cluster from the Ag37 to Ag46 nanowheel driven by heteroanions

Precise control over the shape and size of metal nanoclusters through anion template-driven self-assembly is one of the key scientific goals in the nanocluster community, however, it is still not understood comprehensively. In this work, we report the controllable synthesis and atomically precise structures of silver nanowheels Ag37 and Ag46, using homo (Cl^- ions) and heteroanion (Cl^- and CrO₄ ^2- ions) template strategies, along with macrocyclic p-phenyl-thiacalix[4]arene and small ⁱPrS^- ligands. Structural analyses revealed that in Ag37, Cl^- ions serve as both local and global templates, whereas CrO₄ ^2- ions function as local and Cl^- ions as global templates in Ag46, resulting in a pentagonal nanowheel (Ag37) and a hexagonal (Ag46) nanowheel. The larger ionic size and more negative charges of CrO₄ ^2- ions than Cl^- ions offer more coordination sites for the silver atoms and are believed to be the key factors that drive the nanowheel core to expand significantly. Also, by taking advantage of the deep cavity of thiacalix[4]arene with an extended phenyl group, Ag46 has been used as a host material for dye adsorption depending on the charge and size of organic dyes. The successful use of heteroanions to control the expansion of well-defined silver nanowheels fills the knowledge gap in understanding the directing role of heteroanions in dictating the shape and size of nanoclusters at the atomic level.

Ficus-mediated green synthesis of manganese oxide nanoparticles for adsorptive removal of malachite green from surface water

The extract of ficus leaves was used to prepare manganese (IV) oxide nanoparticles (MnO2 NPs) for the first time. Several different analytical techniques were used to characterize the prepared MnO2 NPs. MnO2 has spherical crystals that are ~ 7 nm on average in size and have 149.68 m2/g of surface area and 0.91 cm3/g of total pore volume. Malachite green (MG) dye was then taken out of the water by adsorption using MnO2 NPs. Optimization of various adsorption parameters resulted in 188.68-277.78 mg/g maximum adsorption capacities at 298-328 K tested temperatures and 99.6% removal of 50 mg/L MG within 90 min using MnO2 dose of 0.01 g at pH 10 and 298 K. The results were tested using pseudo-first order, pseudo-second order, intraparticle diffusion, Elovich, and Liquid film kinetic models as well as Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherm models. The most likely models to describe the adsorption process at 298 K are pseudo-second-order kinetics (R2 = 0.997) with a rate constant of 4 × 10-4 g/(mg.min) and Langmuir isotherm (R2 = 0.973). Additionally, the positive values of enthalpy change (3.91-67.81 kJ/mol) and the negative values of Gibb's free energy (- 3.38 to - 19.7 kJ/mol) indicate that the process is endothermic, spontaneous, and thermodynamically feasible. MnO2 NPs sustained their adsorption efficiency at 90.4% after 5 sorption cycles. MnO2 appears to be more selective for MG in studies examining the adsorption of various cationic dyes. Lately, the biosynthesized MnO2 NPs can be utilized to remove MG from aqueous solutions effectively.

Recent advances in the design and use of Pickering emulsions for wastewater treatment applications

Pickering emulsions have recently emerged as versatile systems capable of targeting many applications of wastewater treatment. The unique properties, which include high emulsion stability, easy preparation, low toxicity, and stimuli-responsiveness, pave the way for advances in common pollutant control processes. This review aims to provide a comprehensive overview on different aspects in the Pickering emulsion design focusing on the key structural relations and their implications in specific applications. The first section is dedicated to the critical parameters governing the Pickering emulsion type, droplet size and stability. Furthermore, a section describing methods for demulsification and particle recovery is included, in which various stimuli have been explored. Finally, the most potent applications of Pickering emulsions such as photocatalytic degradation, adsorption, extraction, and separation of common wastewater pollutants are presented and discussed with a great deal of attention towards the efficacy, current limitations, and future potential. Recognizing the rise of innovative Pickering emulsion solutions is expected to induce profound effects facilitating the technology transfer to industrial processes.

A magnetically recyclable lignin-based bio-adsorbent for efficient removal of Congo red from aqueous solution

It has been always attractive to design a sustainable bio-derived adsorbent based on industrial waste lignin for removing organic dyes from water. However, existing adsorbent strategies often lead to the difficulties in adsorbent separation and recycling. Herein, we report a novel magnetically recyclable bio-adsorbent of Mg(OH)₂/Fe₃O₄/PEI functionalized enzymatic lignin (EL) composite (EL-PEI@Fe₃O₄-Mg) for removing Congo red (CR) by Mannish reaction and hydrolysis-precipitation. The Mg(OH)₂ and PEI functionalized EL on the surface act as active sites for the removal of CR, while the Fe₃O₄ allows for the easy separation under the help of a magnet. As-obtained EL-PEI@Fe₃O₄-Mg forms flower-like spheres and has a relatively lager surface area of 24.8 m² g^-1 which is 6 times that of EL. The EL-PEI@Fe₃O₄-Mg exhibits a relatively high CR adsorption capacity of 74.7 mg g^-1 which is 15 times that of EL when initial concentration is around 100 mg L^-1. And it can be easily separated from water by applying an external magnetic field. Moreover, EL-PEI@Fe₃O₄-Mg shows an excellent anti-interference capability according to the results of pH values and salt ions influences. Importantly, EL-PEI@Fe₃O₄-Mg possesses a good reusability and a removal efficiency of 92 % for CR remains after five consecutive cycles. It is illustrated that electrostatic attraction, π-π interaction and hydrogen binding are primary mechanisms for the removal of CR onto EL-PEI@Fe₃O₄-Mg. This work provides a novel sustainable strategy for the development of highly efficient, easy separable, recyclability bio-derived adsorbents for removing organic dyes, boosting the efficient utilization of industrial waste lignin.

Removal of methylene blue dye from aqueous solution using an efficient chitosan-pectin bio-adsorbent: kinetics and isotherm studies

Wastewater contains organic compounds, including dyes, which have potential risks to the environment. Hence, these compound needs to be eliminated from the aqueous solution. In the present study, chitosan-pectin composite (Cs-Pc) was used as an adsorbent to remove methylene blue dye (MB) from synthetic wastewater. To evaluate the parameters affecting adsorption, including the initial MB concentration, solution pH, contact time, and Cs-Pc dose, batch experiments were carried out. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared (FTIR), and pH point of zero charges (pH pzc) were applied for characterizations of Cs-Pc. The optimum conditions were obtained with an initial MB concentration of 50 mg L^-1: solution pH ~ 11, Cs-Pc dose: 1.5 g L^-1 and 180 min contact time, which caused 97.77% of MB removal. In addition, the removal efficiency of MB was more influenced by pH than by sorbate dose. Also, Cs-Pc had a higher ability to remove MB than chitosan and pectin, probably due to its highly porous structure and rough surfaces that provides active sites and facilitate MB adsorption. The maximum removal efficiency and the adsorption capacity of MB onto Cs-Pc at 500 mg L^-1 concentration under optimum conditions were 98.67% and 328.02 mg g^-1, respectively. The adsorption kinetics and isotherms were best described by pseudo-second-order and Freundlich equation, respectively. After four times of recycling, the removal efficiency of MB was above 96%. Electrostatic and pi-pi interactions are the main mechanisms for the removal of MB onto the adsorbent. So the application of Cs-Pc is promising for MB removal from polluted solutions not only due to its strong adsorbing capability but also due to its excellent ability to reuse.

Sustainable phosphorylated microcrystalline cellulose toward enhanced removal performance of methylene blue

In this study, microcrystalline cellulose (MCC) was phosphorylated using phosphoric acid in the presence of urea and used as an adsorbent for methylene blue (MB) dye removal from an aqueous solution. The obtained products were characterized by different techniques. Batch adsorption experiments were conducted under varying conditions of incubation time, initial MB concentration, pH, and phosphorylation degree. All the samples exhibited similar and fast adsorption kinetics, described by pseudo-second-order model for MB adsorption, whereas the retention capacity depended significantly on the phosphate content and the surface charge of the adsorbents. The experimental adsorption data in the examined MB initial concentrations (0-2000 mg/L) were best suited by the Langmuir isotherm model. The study revealed that the presence of phosphates groups in the cellulose structure significantly enhanced the adsorption of the MB pollutant. The maximum dye removal capacity at pH of 7 was obtained for the phosphorylated microcrystalline cellulose (284.03 mg/g) with a high phosphorylation degree (1.92 % of P), which is 20 times higher than unmodified MCC (15.29 mg/g). This property increased from 284.03 to 328.32 mg/g when increasing the pH from 7 to 11. The MB adsorption mechanism involves hydrogen bonding, electrostatic and ion-dipole interactions. These findings are relevant to a better understanding of the role of cellulose phosphorylation in the recovery of organic dyes from the waste liquid of many industries.

Optimization of Adsorption Parameters for Removal of Cationic Dyes on Lignocellulosic Agricultural Waste Modified by Citric Acid: Central Composite Design

Barley straw (BS-C) and corn stalks (CS-C) modified by citric acid are hopeful adsorbents for the removal of cationic dyes from aqueous solutions. Optimization of adsorption factors to improve removal of methylene blue (MB) and malachite green (MG) on BC-C and CS-C was carried out by response surface methodology with central composite design. The effect of pH, time, dye concentration, and adsorbent dose on the removal efficiency of cationic dyes was investigated. The experimental data were in good agreement with the predicted data obtained by mathematical models. Accordingly, the maximum MB removal efficiency on BS-C of 97% was achieved with a pH of 6.4, time of 50 min, an adsorbent dose of 11 g L−1, and an initial MB concentration of 26 mg L−1; the maximum MG removal efficiency on BS-C of 95% was achieved with a pH of 7.2, time of 60 min, an adsorbent dose of 14 g L−1, and an initial MG concentration of 24 mg L−1; the maximum MB removal efficiency on CS-C of 97% was achieved with a pH of 6.5, time of 45 min, an adsorbent dose of 11 g L−1, and an initial MB concentration of 20 mg L−1; the maximum MG removal efficiency on CS-C of 94% was achieved with a pH of 6.6, time of 50 min, an adsorbent dose of 12 g L−1, and an initial MG concentration of 24 mg L−1.

Bamboo Nanocellulose/Montmorillonite Nanosheets/Polyethyleneimine Gel Adsorbent for Methylene Blue and Cu(II) Removal from Aqueous Solutions

In recent years, the scarcity of pure water resources has received a lot of attention from society because of the increasing amount of pollution from industrial waste. It is very important to use low-cost adsorbents with high-adsorption performance to reduce water pollution. In this work, a gel adsorbent with a high-adsorption performance on methylene blue (MB) and Cu(II) was prepared from bamboo nanocellulose (BCNF) (derived from waste bamboo paper) and montmorillonite nanosheet (MMTNS) cross-linked by polyethyleneimine (PEI). The resulting gel adsorbent was characterized by Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (SEM), X-ray photoelectron spectroscopic (XPS), etc. The results indicated that the MB and Cu(II) adsorption capacities of the resulting gel adsorbent increased with the solution pH, contact time, initial concentration, and temperature before equilibrium. The adsorption processes of MB and Cu(II) fitted well with the fractal-like pseudo-second-order model. The maximal adsorption capacities on MB and Cu(II) calculated by the Sips model were 361.9 and 254.6 mg/g, respectively. The removal of MB and Cu(II) from aqueous solutions mainly included electrostatic attraction, ion exchange, hydrogen bonding interaction, etc. These results suggest that the resulting gel adsorbent is an ideal material for the removal of MB and Cu(II) from aqueous solutions.

A critical review on the synthesis of NH2-MIL-53(Al) based materials for detection and removal of hazardous pollutants

Nowadays, emerging hazardous pollutants have caused many harmful effects on the environment and human health, calling for the state of the art methods for detection, qualification, and treatment. Metal-organic frameworks are porous, flexible, and versatile materials with unique structural properties, which can solve such problems. In this work, we reviewed the synthesis, activation, and characterization, and potential applications of NH₂-MIL-53(Al). This material exhibited intriguing breathing effects, and obtained very high surface areas (182.3-1934 m²/g) with diverse morphologies. More importantly, NH₂-MIL-53(Al) based materials could be used for the detection and removal of various toxic pollutants such as organic dyes, pharmaceuticals, herbicides, insecticides, phenols, heavy metals, and fluorides. We shed light on plausible adsorption mechanisms such as hydrogen bonds, π-π stacking interactions, and electrostatic interactions onto NH₂-MIL-53(Al) adsorbents. Interestingly, NH₂-MIL-53(Al) based adsorbents could be recycled for many cycles with high stability. This review also recommended that NH₂-MIL-53(Al) based materials can be a good platform for the environmental remediation fields.

Adsorptive removal of hazardous dye (crystal violet) using bay leaves (Laurus nobilis L.): surface characterization, batch adsorption studies, and statistical analysis

In this study, the surface properties of Laurus nobilis L. were determined by inverse gas chromatography. From this, the surface of Laurus nobilis L. was found to be an acidic ([Formula: see text]). Then, the adsorption of hazardous crystal violet dye on Laurus nobilis L. was examined. For the adsorption process, the optimum conditions were determined as contact time (60 min), adsorbent dosage (1.0 g/L), agitation rate (200 rpm), and initial pH (≅ 7). The efficiencies of initial concentration, contact time, temperature, and their binary combinations on the improvement of adsorption percentage were statistically investigated via three different two-way ANOVA analyses. Adsorption data were applied to different isotherms, and it was determined that the Langmuir isotherm (r² = 0.9998) was the most suitable isotherm for the adsorption process. The [Formula: see text] value was calculated as 400.0 mg/g at 25 °C from the Langmuir isotherm. According to kinetic models, it was observed that the adsorption occurred in three steps. According to enthalpy (+ 7.52 kJ/mol), activation energy (+ 8.91 kJ/mol), and Gibbs free energy (- 30.0 kJ/mol) values, it was determined that the adsorption occurred endothermically and spontaneously. As a result of reusability studies, it was determined that the adsorbent could be used repeatedly.

Versatile crosslinking synthesis of an EDTA-modified UiO-66-NH2/cotton fabric composite for simultaneous capture of heavy metals and dyes and efficient degradation of organophosphate

The metal-organic frameworks/cotton fabric composites (MOFs/CFCs) have emerged as a new type of prospective materials for environmental cleanup, due to their convenient recyclability and high removal efficiency towards hazardous pollutants. However, their practical applications are limited by complicated synthetic conditions, insufficient interface bonding and poor adsorption capacity. Herein, for the first time, a robust ethylenediaminetetraacetic acid (EDTA)-functionalized MOFs/CFC is prepared based on UiO-66-NH₂ crystals by using EDTA dianhydride as the cross-linking agent, and applied for simultaneous removal of heavy metals and dyes, as well as degradation of chemical warfare agents. The as-prepared EDTA-UiO-66-NH₂/CFC shows extraordinary monocomponent adsorption performance with maximum adsorption capacity of 158.7, 126.2, 131.5, 117.4 and 104.5 mg/g for Cd(II), Cu(II), methylene blue, crystal violet and safranin O, respectively. Interestingly, in metal-dyes binary system, the uptake of Cu(II) by EDTA-UiO-66-NH₂/CFC increases significantly when co-existing high concentration of dyes. The results indicate that the synergistic and simultaneous removal of both dyes and metal from complex systems can be realized by EDTA-UiO-66-NH₂/CFC via multiple mechanisms. The EDTA-UiO-66-NH₂/CFC also exhibits an outstanding catalytic performance for degrading dimethyl 4-nitrophenylphosphate. Besides, it can be reused for several times without obvious decrease of its adsorption and catalysis efficiencies. More impressively, the cross-linking reaction approach can not only anchor UiO-66-NH₂ crystals firmly onto cotton fabric, but also facilitate in-situ formation of abundant adsorption sties on the adsorbent surface. Therefore, this work offers a simple and versatile synthetic strategy to develop high-performance environmental material for multiple pollutants remediation.

Use of artificial intelligence for optimizing biosorption of textile wastewater using agricultural waste

Most of the dyes are toxic and non-biodegradable in textile industry wastewaters. Therefore, removal of textile dye using agriculture waste becomes crucial for the environment. This can be accomplished by the biosorption process which is the passive uptake of pollutants by agricultural waste. In this study, Response Surface Methodology (RSM), Artificial Neural Network (ANN) and Adaptive Neuro-Fuzzy Inference System (ANFIS) were used to obtain optimum conditions for Methylene Blue (MB) removal using sugarcane bagasse and peanut hulls as low-cost agricultural waste. The experimental design was carried out to study the effect of temperature, pH, biosorbent amount and dye concentration. The maximum MB dye removal considering the effect of total dissolved solids from aqueous solutions of 74.49% and 67.99% by sugarcane bagasse and peanut hulls, respectively. The models specify that they could predict biosorption with high accuracy having R2-value above 0.9. Statistical studies for RSM, ANFIS and ANN models were compared. Further, the models were optimized for maximum dye removal was at 1.21 g of biosorbent, pH 5.24, 31.24 mg/L MB concentration, 22.29°C of dye solution using sugarcane bagasse and at 1.37 g of biosorbent, pH 5.77, 36.7 mg/L MB concentration, 26.8°C of dye solution using peanut hulls. Additionally, Fourier Transform Infra-Red (FTIR) spectral analysis was also carried out to confirm the biosorption.