Synthesis of magnetic oxidized multiwalled carbon nanotube-κ-carrageenan-Fe 3 O 4 nanocomposite adsorbent and its application in cationic Methylene Blue dye adsorption

Hollow multi-shelled MOF derivative adsorbent for efficient magnetic solid-phase extraction of several typical endocrine disrupting compounds from water

Bisphenols and benzophenones are two typical kinds of endocrine-disrupting compounds (EDCs) that have been extensively detected in water environments, posing unanticipated risks to aquatic organisms and humans. It is urgent to develop efficient sample pretreatment methods for precise measurement of such EDCs. In this study, a magnetic and multi-shelled metal-organic framework derivative material has been prepared to extract and enrich trace bisphenols and benzophenones from water. Via a solvothermal reaction induced by sodium citrate followed by a carbonization treatment, a ZIF-67@ZIF-8 derived CoZn-magnetic hierarchical carbon (CoZn-MHC) material has been synthesized as a high-performance magnetic solid-phase extraction (MSPE) adsorbent. This adsorbent exhibited a good specific surface area (213.80 m2⋅g-1) and a saturation magnetization of 63.2 emu·g-1. After the optimization of several parameters (including adsorbent dosage, extraction time, pH, ionic strength, desorption solvent, and solvent volume), an efficient MSPE method for several EDCs (comprising bisphenols and benzophenones) was developed with a good linear range (R2 ≥ 0.990), a high sensitivity range (LODs: 0.793-5.37 ng⋅L-1), and good reusability (RSD ≤4.67 % in five consecutive tests). Furthermore, the material exhibited commendable resistance to matrix interference in natural water samples with the recovery rates of target compounds ranging from 74.8 % to 107 %. We envision that the preparation strategy of this functional metal-organic framework (MOF)-based adsorbent for EDCs may provide insights for relevant research in the future.

Fabrication of graphitic carbon nitride/gum Arabic/potassium carrageenan composite for efficient adsorption of erythromycin: Kinetic and thermodynamic studies

Erythromycin (ERY) molecules are robust to the environment and hard to remove due to their aromatic structure. Nowadays, numerous researches have reported that the ERY amount in water is above the standard level and its removal is necessary. Here, we prepared three solid adsorbents: graphitic carbon nitride (g-C3N4), potassium carrageenan beads (Cr), and graphitic carbon nitride/gum Arabic/potassium carrageenan composite (g-ACr). Several techniques such as XRD, SEM, TEM, TGA, ATR-FTIR, Zeta potential, and N2 adsorption were employed to characterize the fabricated adsorbents. Five essential factors of adsorbent dose, initial ERY concentration, contact time, temperature, and pH were optimized to investigate the batch adsorption of ERY. The maximum adsorption capacity of 356.12 mg/g was attained by g-ACr composite at an adsorbent dose of 1.25 g/L, contact time of 6 h, and pH 7 at 15 °C. The data showed that the experimental findings exhibited the best agreement with Langmuir, Temkin, and DR isotherm models, in addition to the kinetic models of pseudo-second-order, Elovich, and intra-particle diffusion. The evaluated thermodynamic factors designated that the ERY adsorption is endothermic, physisorption, favorable, and spontaneous process. The g-ACr reusability displayed a decline in the adsorption capacity after seven adsorption/desorption runs by 5.7 %. Finally, this work outcomes depict that g-ACr composite is an efficient reusable adsorbent for ERY elimination from wastewater.

Lanthanum hydroxide@cellulose membranes with tunable pore sizes for selective removal of dyes with the same charges

Adsorptive membranes for the efficient separation of dyes with the same charges are quite desirable. Herein, a novel membrane of lanthanum hydroxide/cellulose hydrogel coated filter paper (LC) was prepared through a facile strategy of dip-coating followed by freeze-shaping. With the aid of cellulose gel, the generated La(OH)3 achieved fine dispersion. In addition, the pore size of LC membrane could be regulated by altering the cellulose concentration or the lanthanum chloride dosage, which was crucial for its water flux. In particular, the obtained membrane possessed a high water flux (128.4 L m-2 h-1) and a high dye rejection (97.2 %) for anionic Congo red (CR) only driven by the gravity, which outperformed many previously reported membranes. More intriguingly, its dye rejection for anionic methyl orange (MO) was only 0.9 %, exhibiting high selectivity for dyes with the same charges. Single-solute adsorption experiments indicated that the CR adsorption on the membrane was best fitted by the pseudo-first-order kinetic model, and it followed the Langmuir monolayer adsorption mechanism.

Clay-polymer nanocomposites for effective water treatment: opportunities, challenges, and future prospects

The metal intoxication and its associated adverse effects to humans have led to the research for development of water treatment technologies from pollution hazards. Therefore, development of cheaper water remediation technologies is more urgent than ever. Clays and clay minerals are naturally occurring, inexpensive, non-toxic materials possessing interesting chemical and physical properties. As a result of interesting surface properties, these have been developed as efficient absorbent in water remediation. Recently, clay-polymer nanocomposites have provided a cost-effective technological platform for removing contaminants from water. Covering research advancements from past 25 years, this review highlights the developments in clay-polymer nanocomposites and their advanced technical applications are evaluated with respect to the background and issues in remediation of toxic metals and organic compounds from water. The extensive analysis of literature survey of more than two decades suggests that future work need to highlight on advancement of green and cost-effective technologies. The development of understanding of the interaction and exchange between toxin and clay-polymer composites would provide new assembly methods of nanocomposites with functional molecules or nanomaterials need to be extended to increase the detection and extraction limit to parts per trillion.

Purification of aqueous orange II solution through adsorption and visible-light-induced photodegradation using ZnO-modified g-C3N4 composites

Semiconductor-based remediation enables environmentally friendly methods of removing aqueous pollutants. Simply fabricated ZnO modified g-C3N4 composites were utilized as bifunctional adsorptive photocatalysts for orange II removal from aqueous solution through adsorption and photocatalysis processes. The adsorption isotherm data of the g-C3N4 (g-CN) and ZnO modified g-C3N4 (ZCN) composites on orange II solution were better fitted with the Langmuir isotherm compared to the Freundlich isotherm. The maximum adsorption capacity for ZCN-2.5 was slightly higher than that of bare g-CN. According to the adsorption thermodynamics investigation of ZCN-2.5 in orange II solution, the positive values of Gibb's free energy change (ΔG0) suggested a non-spontaneous adsorption process. Furthermore, the negative values of entropy change (ΔS) and enthalpy change (ΔH) indicated the decrement of randomness and exothermic nature during the adsorption process, respectively. The photocatalytic degradation kinetics of g-CN and ZCN composites indicated that the degradation process follows the pseudo-first-order reaction kinetic. The degradation rate of orange II with the ZCN-2.5 composite was 6.67 times higher than that obtained with bare g-CN. Possible adsorption and photocatalytic mechanisms have been proposed.

Efficient dye adsorption of mesoporous activated carbon from bamboo parenchyma cells by phosphoric acid activation

In order to solve the environmental damage caused by the discharge of dyes as industrial wastewater, the development of efficient and sustainable adsorbents is the key, while most of the previous studies on bamboo parenchyma cells have focused on their microstructural, functional and mechanical properties, and few of the properties in adsorption have been investigated. To evaluate the role of the unique microstructure of bamboo parenchyma cells on adsorption after carbonization and activation, PC-based activated carbon (PPAC) was fabricated by the phosphoric acid activation method and tested for adsorption using methylene blue (MB). The effect of mesoporous structure on MB adsorption was investigated in detail using PPAC-30C impregnated with phosphoric acid at a concentration of 30%. The results showed that the adsorption performance was influenced by single-factor experiments (e.g., pH, activated carbon dosing). The adsorption isotherms and kinetics could conform to the Langmuir model (R2 = 0.983-0.994) and pseudo-second-order kinetic model (R2 = 0.822-0.991) respectively, and the maximum MB adsorption capacity of adsorbent was 576 mg g-1. The adsorption mechanism of MB on PPAC-30C includes physical adsorption, electrostatic attraction, hydrogen bonding, and the π-π conjugation effect, which was dominated by physical adsorption. The results of this study show that PPAC has good application prospects for cationic dye removal.

Synergistic adsorption of methylene blue with carrageenan/hydrochar-derived activated carbon hydrogel composites: Insights and optimization strategies

The study explores the use of hydrochar-derived activated carbon (AC) to improve the adsorption capacity and mechanical properties of carrageenan (CAR) hydrogel beads. Four distinct samples, with carrageenan to activated carbon ratios of 1:0 (CAR), 2:1 (CAC2), 4:1 (CAC4), and 10:1 (CAC10), were prepared. These polymeric beads underwent comprehensive evaluation for their methylene blue (MB) adsorption capacity, gel content (GC), and swelling ratio (SR). Increasing activated carbon content up to 50 % of carrageenan mass significantly enhanced GC and SR by 20.57 % and 429.24 %, respectively. Various analytical techniques were employed to characterize the composites, including FTIR, XRD, Raman Spectroscopy, BET, SEM, and EDS-Mapping. Batch adsorption tests investigated the effects of pH, contact time, dye concentration, and temperature on MB adsorption. Maximum adsorption capacities for CAR, CAC10, CAC4, and CAC2 were 475.48, 558.54, 635.93, and 552.35 mg/g, respectively, under optimal conditions. Kinetic models (Elovich and pseudo-second-order) and isotherm models (Temkin for CAR and Freundlich for CAC10, CAC4, and CAC2) fitted well with the experimental data. Thermodynamic analysis showed spontaneous, exothermic MB adsorption. Primary mechanisms include electrostatic attraction, hydrogen bonding, n-π, and π-π stacking. The study highlights enhanced adsorption capacity of carrageenan hydrogel via carrageenan/activated carbon composites, providing cost-effective wastewater treatment.

Efficient treatment of oily wastewater, antibacterial activity, and photodegradation of organic dyes using biosynthesized Ag@Fe3O4 nanocomposite

A significant waste (e.g., high oil content and pollutants such as heavy metals, dyes, and microbial contaminants) in water is generated during crude oil extraction and industrial processes, which poses environmental challenges. This study explores the potential of Ag@Fe3O4 nanocomposite (NC) biosynthesized using the aqueous leaf extract of Laurus nobilis for the treatment of oily wastewater. The NC was characterized using ultraviolet-visible (UV-Vis) spectrophotometry, Scanning Electron Microscopy (SEM), Fourier Transformed Infrared (FTIR) and X-Ray Diffraction (XRD) spectroscopies. The crystalline structure of the NC was determined to be face-centered cubic with an average size of 42 nm. Ag@Fe3O4 NC exhibited significant degradation (96.8%, 90.1%, and 93.8%) of Rose Bengal (RB), Methylene Blue (MB), and Toluidine Blue (TB), respectively, through a reduction reaction lasting 120 min at a dye concentration of 10 mg/L. The observed reaction kinetics followed a pseudo-first-order model, with rate constants (k-values) of 0.0284 min-1, 0.0189 min-1, and 0.0212 min-1 for RB, MB, and TB, respectively. The fast degradation rate can be attributed to the low band gap (1.9 eV) of Ag@Fe3O4 NC. The NC elicited an impressive effectiveness (99-100%, 98.0%, and 91.8% within 30 min) in removing, under sunlight irradiation, several heavy metals, total petroleum hydrocarbons (TPH), and total suspended solids (TSS) from the oily water samples. Furthermore, Ag@Fe3O4 NC displayed potent antibacterial properties and a good biocompatibility. These findings contribute to the development of efficient and cost-effective methods for wastewater treatment and environmental remediation.

Synthesis and characterization of Alg/Gel/n-HAP/MNPs porous nanocomposite adsorbent for efficient water conservancy and removal of methylene blue in aqueous environments: Kinetic modeling and artificial neural network predictions

In this study, a new porous nanocomposite adsorbent for water conservancy was synthesized using the freeze-drying technique to adsorb a cationic dye (Methylene Blue) in an aqueous environment. The nanocomposite adsorbent was synthesized using natural polymers, gelatin, and sodium alginate, and hydroxyapatite and magnetic iron oxide nanoparticles was incorporated into the polymer network to improve mechanical properties and increase the surface-to-volume ratio. To confirm the structure and morphology of the sample, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscope (SEM) techniques were employed. In addition, the magnetic properties of the synthesis of MNPs and porous nanocomposite were determined using value stream mapping (VSM) and dynamic light scattering (DLS). The adsorption of Methylene Blue (MB) was studied as a function of effective physical and variable parameters, such as time, temperature, pH, and initial concentration. The synthesized porous nanocomposite adsorbent exhibited a high adsorption capacity of 473.2 mg g-1 and followed pseudo-second-order kinetics. Additionally, the maximum adsorption capacity was observed at an initial concentration of 534.9 mg g-1. The adsorbent was also sensitive to temperature changes and was well-described thermodynamically and isothermally by the Freundlich isotherm model. Two artificial neural networks (ANNs) were also developed to investigate the properties of the synthesized nanocomposites. In the first ANN, the properties of the nanocomposites, including pore size, porosity, compressive strength, and elastic modulus, were predicted based on the variations in the weight percentages of gelatin and hydroxyapatite. In the second ANN, the effects of changes in temperature and initial concentration on the adsorption of MB by the synthesized nanocomposite samples were predicted. The ANNs' predictions indicated that increasing the weight percentage of hydroxyapatite nanoparticles and gelatin enhances the physical, mechanical, and adsorption performance of the synthesized porous nanocomposites. The best results were achieved for the sample containing 40 wt % of gelatin and 30 wt % of hydroxyapatite nanoparticles. Furthermore, the ANN models demonstrated that increasing the temperature and initial concentration resulted in an increase in the amount of MB adsorbed.

New insights on the preparation of amine covalent organic polymer and its adsorption properties

Dye pollution is becoming increasingly severe. This study used the Schiff base reaction to synthesize a polyaromatic ring covalent organic polymer material with amide bonds and high electronegativity named SLEL-9 to adsorb Methylene Blue (MB) and Rhodamine B (RhB). SLEL-9 was characterized by Fourier transform infra-red spectra, X-ray photoelectron spectra, Brunauer-Emmett-Teller (BET), zeta potential analysis, and other techniques. It was found that SLEL-9 material contains C-C, CN, C-N, and CO. SLEL-9 had a zeta potential of about -45 mV under neutral conditions, which proved that the material had been synthesized successfully. The BET and Langmuir surface areas of SLEL-9 were 35.187 m2 g-1 and 56.419 m2 g-1, respectively. The adsorptions of SLEL-9 on low concentration (10 mg L-1) Methylene Blue and Rhodamine B reached equilibrium within 48 h. The results showed that SLEL-9's adsorption of dye molecules are more consistent with pseudo-second-order kinetic and Langmuir isotherm model. The adsorption experiments showed that the adsorption process is a spontaneous endothermic reaction, mainly chemisorption. The maximum adsorption capacity of SLEL-9 for MB and RhB were 132.45 mg g-1 and 101.94 mg g-1. In addition, this study investigated to determine the optimal reaction parameters. The primary mechanisms of SLEL-9 adsorption of two dyes are n→π* interaction, π-π EDA interaction and electrostatic attraction. Selective adsorb ability experiment results showed that SLEL-9 could selectively adsorb MB and RhB to a certain extent. Finally, it was found that SLEL-9 can maintain over 70% adsorption capacity after five reuses and can maintain stability after soaking in different pH water and organic solvents for 120 h. SLEL-9 proved to be a promising organic covalent polymer adsorption material for the removal of Methylene Blue and Rhodamine B in water.

Graphene oxide@Fe3O4-decorated iota-carrageenan composite for ultra-fast and highly efficient adsorption of lead (II) from water

The aggravated problem of lead pollution, especially in aquatic environments, necessitates the development of eminent adsorbents that could radically solve this environmental problem. Hence, a new composite was constructed based on iota carrageenan (i.Carr), graphene oxide (GO) and magnetite (Fe3O4) for removing noxious Pb2+ ions. The GO@Fe3O4-i.Carr composite was characterized by VSM, SEM, XPS, XRD, FTIR and Zeta potential. The removal of Pb2+ ions attained a quick equilibrium of almost 30 min with a removal efficiency reaching 93.68 %. The removal of Pb2+ was boosted significantly, in the order of GO@Fe3O4-i.Carr(1:1) > GO@Fe3O4-i.Carr(1:3) > GO@Fe3O4-i.Carr(3:1). Moreover, acquired experimental data fitted the pseudo 2nd order kinetic model and Freundlich isotherm model with a maximal monolayer adsorption capacity reached 440.05 mg/g. Notably, after five adsorption runs, the composite maintained its removal efficiency exceeding 74 %. The assumed adsorption mechanisms of Pb2+ onto GO@Fe3O4-i.Carr were complexation, precipitation, Lewis acid-base, and electrostatic attraction forces. Overall, the GO@Fe3O4-i.Carr composite elucidated the auspicious adsorbent criteria, comprising fast adsorption with high performance, ease-separation and tolerable recyclability, advising its feasible use to decontaminate water bodies from hazardous heavy metals.

Green preparation of magnetic ferroferric oxide-polyvinyl alcohol-alginate coated UiO-67 nanospheres: Characterization, adsorption properties and adsorption mechanism of methylene blue

In this paper, a kind of magnetic ferric oxide/polyvinyl alcohol/calcium alginate/UiO-67 (Fe3O4/PVA/CA/UiO-67) nanospheres with homogeneous surface interconnecting structures was prepared by using macromolecular polymer polyvinyl alcohol and sodium alginate as carriers and zirconium organic skeleton as nanocrystals. The properties of magnetic nanospheres were studied by SEM, FT-IR, TGA, XRD, BET, VSM and Zeta potential. The impression of diverse temperatures, MB concentrations, interaction time, pH, and magnetic aerogel sphere dose on MB removal was studied. The optimum adsorption temperature and pH of magnetic nanospheres for MB were 298 K, and 10, respectively. Langmuir simulated that the maximum removal of MB by magnetic nanospheres at room temperature (298 K) was 1371.8 mg/g. The removal of MB by magnetic nanospheres complied with the pseudo-first-order kinetic model. The isotherm simulation can infer that the Langmuir model was more comply with MB adsorption on magnetic aerogel spheres. Thermodynamic studies have confirmed that the removal of MB by magnetic nanospheres was exothermic and spontaneous. The interaction mechanism of MB on magnetic nanospheres can be deduced by FT-IR and BET, including hydrogen bond, π-π bond, electrostatic interaction, and mesoporous pore flow. The removal rate of nanospheres for MB still reached 70.06 % after six cycles.

Selective removal of Pb(II) from yellow rice wine using magnetic carbon-based adsorbent

BACKGROUND

The non-distilled property and prolonged production period of yellow rice wine have significantly increased the metal residue problem, posing a threat to human health. In this study, a magnetic carbon-based adsorbent, named magnetic nitrogen-doped carbon (M-NC), was developed for the selective removal of lead(II) (Pb(II)) from yellow rice wine.

RESULTS

The results showed that the uniformly structured M-NC could be easily separated from the solution, exhibiting a high Pb(II) adsorption capacity of 121.86 mg g-1 . The proposed adsorption treatment showed significant Pb(II) removal efficiencies (91.42-98.90%) for yellow rice wines in 15 min without affecting their taste, odor, and physicochemical characteristics of the wines. The adsorption mechanism studied by X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared (FTIR) analyses indicated that the selective removal of Pb(II) could be attributed to the electrostatic interaction and covalent interaction between the empty orbital of Pb(II) and the π electrons of the N species on M-NC. Additionally, the M-NC showed no significant cytotoxicity on the Caco-2 cell lines.

CONCLUSION

Selective removal of Pb(II) from yellow rice wine was achieved using magnetic carbon-based adsorbent. This facile and recyclable adsorption operation could potentially address the challenge of toxic metal pollution in liquid foods. © 2023 Society of Chemical Industry.

Preparation and application of irradiated polyvinyl alcohol/starch/pumice composites for adsorption of basic dye: Isotherm and kinetics study

Even at low concentrations, organic dye pollution entering water resources from the textile, paper, and pharmaceutical industry sectors poses a serious hazard to human and aquatic life. One of the most significant remediation methods is the adsorption method. In the present study, the uptake of basic violet 7 (BV7) synthetic dye was investigated utilizing Poly (vinyl alcohol)/starch/Pumice [poly (PVA/St/Pu)] composite films prepared by a simple casting of both PVA and St with Pu and then irradiated by electron beam (EB) source to prompt curing. Numerous characterization methods, such as SEM, FTIR, X-ray diffraction (XRD, and other measurements, were examined on the prepared sample. The tensile strength (TS) of all composites was increased by increasing the radiation dose up to 10 kGy. TS was increased by 3 php of Pu, and an overload of Pu led to a decrease in TS values. The elongation at break (Eb) of the prepared composite increased at 3 Pu, then decreased as the quantity of the pumice increased, while the Eb was decreased by irradiation. The effects of the produced polymeric films' composition and irradiation dose on the basic violet 7 (BV 7) dye adsorption were studied. It was found that the adsorption capacity of poly (PVA/St/9 php Pu-10 kGy) toward the BV 7 dye was 64.9 mg/g at the optimal conditions: pH = 11, contact time = 480 min., adsorbent dosage = 0.2 g., concentration = 150 mg/l, and temperature = 298 K. The adsorption process fitted with the pseudo-second-order model, Freundlich adsorption isotherms were found to be spontaneous and endothermic.

Adsorption of nitrophenol onto a novel Fe3O4-κ-carrageenan/MIL-125(Ti) composite: process optimization, isotherms, kinetics, and mechanism

Water pollution is a dreadful affair that has incessantly aggravated, exposing our planet to danger. In particular, the persistent nitro aromatic compound like nitrophenols causes anxiety to the researchers due to their hazardous impacts, excessive usage, and removal difficulty. For this purpose, a novel multi-featured composite was constructed based on κ-Carrageenan (κ-Carr), MOF (MIL-125(Ti)), and magnetic Fe3O4 for efficient adsorptive removal of o-nitrophenol (o-NP). Interestingly, BET measurements revealed the high surface area of Fe3O4-κ-Carr/MIL-125(Ti) of about 163.27 m2/g, while VSM showed its excellent magnetic property (20.34 emu/g). The comparison study pointed out the synergistic effect between Fe3O4, κ-Carr, and MIL-125(Ti), forming a composite with an excellent adsorption performance toward o-NP. The adsorption data obeyed pseudo-second-order kinetic model, and Freundlich isotherm model was better fitted than Langmuir and Temkin. Furthermore, Langmuir verified the supreme adsorption capacity of o-NP onto Fe3O4-κ-Carr/MIL-125(Ti) since the computed qmax reached 320.26 mg/g at pH 6 and 25 °C. Furthermore, the XPS results postulated that the adsorption mechanism pf o-NP proceeded via H-bonding, π-π interaction, and electron donor-acceptor interactions. Interestingly, Fe3O4-κ-Carr/MIL-125(Ti) composite retained good adsorption characteristics after reusing for five cycles, suggesting its viable applicability as an efficient, renewable, and easy-separable adsorbent for removing nitro aromatic pollutants.

Synthesis of hybrid framework of tenorite and octahedrally coordinated aluminosilicate for the robust adsorption of cationic and anionic dyes

Adsorption is an important process for the industrial dye effluent treatment. Many adsorbents are employed such as activated carbon, metal oxide, molecular sieves etc. All those adsorbents are having their own setbacks like longer adsorption time and lower adsorption capacity. So development of fast adsorption and higher adsorption capacity is very much essential. In this view, we synthesized hybrid crystal system of tenorite and aluminosilicate framework (CuO@AS) for the faster adsorption. It is characterized by FT-IR, HRTEM and WAXRD. WAXRD proved the hybridization of two crystal systems viz tenorite & alumina in monoclinic phase and silica in trigonal phase. The crystal structure drawn based on the WAXRD data. It is observed that the tenorite and aluminosilicate framework are separate, but they are interlinked through Cu-O-Al and Cu-O-Si bond. This interconnection makes the aluminium in six coordination and Cu in four coordination. Aluminium and copper has 3 and 2 Brønsted acid sites respectively. Moreover, copper has three more OH group, so totally 5 H⁺ and 3 OH^- sites in copper and aluminium are responsible for the faster adsorption with high adsorption capacity compared to reported literature. To test the adsorption tendency, Victoria Blue (VB) and Metanil Yellow (MY) dyes are employed at room temperature. The rate constant of Pseudo-second order kinetics for the VB and MY are 0.002462 g mg^-1 min^-1 and 0.001619 g mg^-1 min^-1 which indicated faster adsorption of VB than MY. Moreover, total adsorption capacity for VB (636 mg/g) is higher than MY (52 mg/g). This is due to the hybridization of tenorite and aluminosilicate. Thermodynamic data such as ΔG°, ΔH° and ΔS° revealed that the adsorption is spontaneous, chemisorption and highly disordered in the adsorbent-adsorbate interface. This disorderness is due to the disordered pores present in the material.

New insights into the degradation and detoxification of methylene blue using heterogeneous-Fenton catalyzed by sustainable siderite

The huge application of synthetic dyes caused a severe impact in the environment. In the present study, a physico-chemical strategy of heterogeneous-Fenton catalyzed by the natural ferrous ore has been established for toxic chemical degradation, of which the complex and high-expense repetitive pH adjustment procedures were escaping. And this natural heterogeneous catalyst also could be recycled and sustainable for toxic substances treatment involved in synergetic adsorption and oxidation. The siderite, served as an adsorbent and catalyst for the degradation of methylene blue (MB). Siderite exhibited a better adsorption capacity with a saturated adsorption capacity of ∼11.08 mg/g. Batch adsorption experiments have verified that adsorption rate and adsorption equilibrium followed pseudo-second-order rate model and Langmuir isotherm equation, respectively. The combination with H₂O₂, showed significant enhancement of MB degradation without any pH adjustment. The effect of siderite dosage, H₂O₂ dosage, MB concentration, initial pH, and reaction temperature on MB degradation was investigated, which also has indicated the excellent catalytic performance of siderite. About 99.71% of MB was degraded in 480 min with initial pH of 7.0, reaction temperature of 25 °C, siderite, and H₂O₂ dosage of 2.5 g/L and 122.38 mM, respectively. It was found that siderite could be reused and remained high degradation efficiency on MB after 5 times reutilization, which also could demonstrate the sustainable and effective process to degrade organic pollution. The generation of reactive species including ·OH and O2·- have been confirmed based on scavenger test and electron spin resonance (ESR) analysis, which was dominated by heterogeneous reaction. The possible degradation mechanisms of MB have been predicted based on spectrum scanning and GC-MS analysis. Moreover, acute toxicity assessment with marine photobacterium Vibrio fisheri was conducted to investigate the toxicity change in the adsorption/oxidation coupled process. This sustainable heterogeneous-Fenton technology has been verified as a promising and applicable process for toxic organic chemicals removal due to effective mineralization and detoxification assisted with the natural ore mineral through the simple operation and mild condtions.

Enhanced adsorption capacity of activated carbon over thermal oxidation treatment for methylene blue removal: kinetics, equilibrium, thermodynamic, and reusability studies

Activated carbon (AC) is an effective and inexpensive adsorbent material for dye removal, but it cannot always be used repeatedly. Furthermore, the adsorbed dyes with toxicity usually remain on its surface. In this study, a thermal air oxidation process was used to modify the surface of AC and decompose adsorbed methylene blue (MB). The behavior of this process on spent AC was investigated using TGA-DTA, while the degradation of MB before and after the regeneration process was analyzed using a carbon, hydrogen, nitrogen, sulfur (CHNS) analyzer. It was discovered that thermal air oxidation could promote the formation of oxygenated functional groups on AC produced from steam-activated carbon coconut shell (SACCS), which when treated at 350 °C (denoted as SACCS-350), demonstrated an adsorption capacity 2.8 times higher than the non-air-oxidized AC (SACCS). The key parameters for the MB adsorption of SACCS and SACCS-350, such as kinetics, equilibrium, and thermodynamics, were compared. Moreover, the SACCS-350 could be reused at least 3 times for the adsorption of MB. Based on these results, thermal air oxidation treatment could successfully improve the adsorption performance of AC and regenerate spent AC through a reasonable and environmentally friendly process compared to other regeneration methods.

Cross-Linked Ionic Liquid Polymer for the Effective Removal of Ionic Dyes from Aqueous Systems: Investigation of Kinetics and Adsorption Isotherms

In the current study, we have synthesized an imidazolium based cross-linked polymer, namely, 1-vinyl-3-ethylimidazolium bis(trifluoromethylsulfonyl)imide (poly[veim][Tf2N]-TRIM) using trimethylolpropane trimethacrylate as cross linker, and demonstrated its efficiency for the removal of two extensively used ionic dyes—methylene blue and orange-II—from aqueous systems. The detailed characterization of the synthesized poly[veim][Tf2N]-TRIM was performed with the help of 1H NMR, TGA, FT-IR and FE-SEM analysis. The concentration of dyes in aqueous samples before and after the adsorption process was measured using an UV-vis spectrophotometer. The process parameters were optimised, and highest adsorption was obtained at a solution pH of 7.0, adsorbent dosage of 0.75 g/L, contact time of 7 h and dye concentrations of 100 mg/L and 5.0 mg/L for methylene blue and orange-II, respectively. The adsorption kinetics for orange-II and methylene blue were well described by pseudo-first-order and pseudo−second-order models, respectively. Meanwhile, the process of adsorption was best depicted by Langmuir isotherms for both the dyes. The highest monolayer adsorption capacities for methylene blue and orange-II were found to be 1212 mg/g and 126 mg/g, respectively. Overall, the synthesized cross-linked poly[veim][Tf2N]-TRIM effectively removed the selected ionic dyes from aqueous samples and provided >90% of adsorption efficiency after four cycles of adsorption. A possible adsorption mechanism between the synthesised polymeric adsorbent and proposed dyes is presented. It is further suggested that the proposed ionic liquid polymer adsorbent could effectively remove other ionic dyes and pollutants from contaminated aqueous systems.

Facile Synthesis and Life Cycle Assessment of Highly Active Magnetic Sorbent Composite Derived from Mixed Plastic and Biomass Waste for Water Remediation

Plastic and biomass waste pose a serious environmental risk; thus, herein, we mixed biomass waste with plastic bottle waste (PET) to produce char composite materials for producing a magnetic char composite for better separation when used in water treatment applications. This study also calculated the life cycle environmental impacts of the preparation of adsorbent material for 11 different indicator categories. For 1 functional unit (1 kg of pomace leaves as feedstock), abiotic depletion of fossil fuels and global warming potential were quantified as 7.17 MJ and 0.63 kg CO₂ equiv for production of magnetic char composite materials. The magnetic char composite material (MPBC) was then used to remove crystal violet dye from its aqueous solution under various operational parameters. The kinetics and isotherm statistical theories showed that the sorption of CV dye onto MPBC was governed by pseudo-second-order, and Langmuir models, respectively. The quantitative assessment of sorption capacity clarifies that the produced MPBC exhibited an admirable ability of 256.41 mg g^-1. Meanwhile, the recyclability of 92.4% of MPBC was demonstrated after 5 adsorption/desorption cycles. Findings from this study will inspire more sustainable and cost-effective production of magnetic sorbents, including those derived from combined plastic and biomass waste streams.

Environmentally benign approach for the efficient sequestration of methylene blue and coomassie brilliant blue using graphene oxide emended gelatin/κ-carrageenan hydrogels

Herein, we report the synthesis and characterization of gelatin/κ-carrageenan crosslinked polyacrylic acid hydrogel (GT-CAG-cl-polyAA) and graphene oxide incorporated hydrogel nanocomposite (GO_HNC) through a free radical crosslinking pathway. Under optimized reaction conditions, GT-CAG-cl-polyAA displayed 486 % maximum swelling percentage. TEM image depicted wrinkled silk veil wave-type surface morphology of graphene oxide (GO), whereas, the SEM analysis indicated the porous nature of the GT-CAG-cl-polyAA and GO_HNC capable of accumulating a large number of water/dye molecules. GT-CAG-cl-polyAA exhibited 96.11 % and 82.16 % dye removal potential for the adsorption of methylene blue (MB) and coomassie brilliant blue (CB), respectively under optimized conditions. GO_HNC enhanced the % dye removal efficiency (98.39 % for MB and 94.50 % for CB). The maximum adsorption capacity of GO_HNC for the removal of CB and MB was 312.7 mg/g and 94.9 mg/g, respectively. The adsorption of CB and MB exhibited best fitting with Flory-Huggins adsorption isotherms data. The negative values of ΔG° and positive values of ΔS° which were obtained from the adsorption isotherm plot suggested the thermodynamic feasibility of the adsorption. Also, the samples were reusable for up to five consecutive cycles without any degradation and hence suggested a considerable pathway for the separation of textile dyes.

Taguchi L25 (54) Approach for Methylene Blue Removal by Polyethylene Terephthalate Nanofiber-Multi-Walled Carbon Nanotube Composite

A membrane composed of polyethylene terephthalate nanofiber and multi-walled carbon nanotubes (PET NF-MWCNTs) composite is used to adsorb methylene blue (MB) dye from an aqueous solution. Scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction techniques are employed to study the surface properties of the adsorbent. Several parameters affecting dye adsorption (pH, MB dye initial concentration, PET NF-MWCNTs dose, and contact time) are optimized for optimal removal efficiency (R, %) by using the Taguchi L25 (54) Orthogonal Array approach. According to the ANOVA results, pH has the highest contributing percentage at 71.01%, suggesting it has the most significant impact on removal efficiency. The adsorbent dose is the second most affected (12.08%), followed by the MB dye initial concentration of 5.91%, and the least affected is the contact time (1.81%). In addition, experimental findings confirm that the Langmuir isotherm is well-fitted, suggesting a monolayer capping of MB dye on the PET-NF-MWCNT surface with a maximum adsorption capacity of 7.047 mg g−1. Also, the kinetic results are well-suited to the pseudo-second-order model. There is a good agreement between the calculated (qe) and experimental values for the pseudo-second-order kinetic model.

Preparation and characterisation of graphene oxide containing block copolymer worm gels

This paper reports a generic method for preparing reinforced nanocomposite worm-gels. Aqueous poly(glycerol monomethacrylate)-b-poly(2-hydroxypropyl methacrylate) (PGMA-PHPMA) and methanolic poly(glycerol monomethacrylate)-b-poly(benzyl methacrylate) (PGMA-PBzMA) worm gels were prepared by RAFT-mediated polymerisation-induced self-assembly (PISA). The former system undergoes a reversible worm-to-sphere degelation transition upon cooling to 5 °C whilst the latter system undergoes the same transition on heating to 56 °C. This transition allows these copolymer dispersions to be readily mixed with graphene oxide (GO) whilst in a low viscosity state and form nanocomposite gels on returning to room temperature via a sphere-to-worm transition. Various quantities of GO were added to the studied copolymer dispersions at a fixed copolymer content of 15% w/w. A general trend was observed whereby relatively small quantities of GO caused the gel strength of the nanocomposite gel to be higher than that of the pristine worm-gel, as determined by oscillatory rheology. Additional quantities of GO resulted in gel weakening or prevented gel-reformation altogether. For instance, 15% w/w PGMA₅₂-PHPMA₁₃₀ worm gels had a storage modulus (G') of approximately 1.5 kPa. The addition of 1.5% w/w GO based on the copolymer caused G' to increase to approximately 4.0 kPa but >1.5% w/w GO resulted in gel strengths <1.0 kPa. A combination of aqueous electrophoresis and transmission electron microscopy measurements were used to investigate the mechanism of nanocomposite gel formation. It was observed that the PGMA-based copolymers readily absorb onto the surface of GO. Thus, the role of GO is both to strengthen the worm-gels when an optimal concentration of GO is used, but also prevent worm-reformation if too much copolymer becomes absorbed on the surface of the sheets.

The Adsorption of Copper, Lead Metal Ions, and Methylene Blue Dye from Aqueous Solution by Pure and Treated Fennel Seeds

This research work reports on pure and acid-treated fennel seed biomaterials for the removal of metal ions of copper Cu(II), lead Pb(II), and methylene blue (MB) dye from aqueous solution by batch adsorption. Pure fennel seeds were labelled as PFS; nitric and sulphuric acid-treated seeds were designated as NAFS and SAFS, respectively. The adsorbents were characterised by SEM, EDX, FTIR, XRD, and BET. The SEM images revealed that the surface of the adsorbents was porous. However, physicochemical characterization further revealed that BET surface area, pore size, and pore width increased for NAFS and SAFS compared to PFS. FTIR results revealed that the peaks for cellulose −COC and −OH decreased considerably for NAFS and SAFS; this indicated that cellulose was hydrolyzed during acid treatment. Adsorption data showed that all biomaterials had a higher affinity for MB dye more than Pb(II) and Cu(II) metal ions. The maximum adsorption capacities onto PFS were 6.834, 4.179, and 2.902 mg/g and onto NAFS are 15.28, 14.44, and 4.475 mg/g, while those onto SAFS are 19.81, 18.79 and 6.707 mg/g respective for MB dye, Pb(II), and Cu(II) ions. Postadsorption analysis revealed that adsorption of Pb(II) and Cu(II) was controlled mainly by the electrostatic attraction, while that of MB was synergistic of electrostatic attraction, π-π interaction, and hydrogen bond. It was found that the uptake processes of MB dye onto all adsorbents fitted Freundlich while both cations were described by Langmuir model. The thermodynamic parameters $\Delta H$ o and $\Delta G$ o indicated the endothermic nature and spontaneity of the processes, respectively.

Recent Developments in the Application of Bio-Waste-Derived Adsorbents for the Removal of Methylene Blue from Wastewater: A Review

Over the last few years, various industries have released wastewater containing high concentrations of dyes straight into the ecological system, which has become a major environmental problem (i.e., soil, groundwater, surface water pollution, etc.). The rapid growth of textile industries has created an alarming situation in which further deterioration to the environment has been caused due to substances being left in treated wastewater, including dyes. The application of activated carbon has recently been demonstrated to be a highly efficient technology in terms of removing methylene blue (MB) from wastewater. Agricultural waste, as well as animal-based and wood products, are excellent sources of bio-waste for MB remediation since they are extremely efficient, have high sorption capacities, and are renewable sources. Despite the fact that commercial activated carbon is a favored adsorbent for dye elimination, its extensive application is restricted because of its comparatively high cost, which has prompted researchers to investigate alternative sources of adsorbents that are non-conventional and more economical. The goal of this review article was to critically evaluate the accessible information on the characteristics of bio-waste-derived adsorbents for MB's removal, as well as related parameters influencing the performance of this process. The review also highlighted the processing methods developed in previous studies. Regeneration processes, economic challenges, and the valorization of post-sorption materials were also discussed. This review is beneficial in terms of understanding recent advances in the status of biowaste-derived adsorbents, highlighting the accelerating need for the development of low-cost adsorbents and functioning as a precursor for large-scale system optimization.

Cellulose Nanofiber-Based Aerogels from Wheat Straw: Influence of Surface Load and Lignin Content on Their Properties and Dye Removal Capacity

Water pollution is one of the most serious problems worldwide. Nanocellulose-based aerogels usually show excellent adsorption capacities due to their high aspect ratio, specific surface area and surface charge, making them ideal for water purification. In this work, (ligno)cellulose nanofibers (LCNFs/CNFs) from wheat straw residues were obtained using two types of pre-treatments: mechanical (Mec) and TEMPO-mediated oxidization (TO), to obtain different consistency (0.2, 0.4, 0.6 and 0.8) bioaerogels, and their adsorption capacities as dye removers were further studied. The materials were characterized in terms of density, porosity and mechanical properties. An inversely proportional relationship was observed between the consistencies of the aerogels and their achieved densities. Despite the increase in density, all samples showed porosities above 99%. In terms of mechanical properties, the best results were obtained for the 0.8% consistency LCNF and CNF-Mec aerogels, reaching 67.87 kPa and 64.6 kPa for tensile strength and Young’s modulus, respectively. In contrast, the adsorption capacity of the aerogels was better for TEMPO-oxidized aerogels, reaching removal rates of almost 100% for the CNF-TO5 samples. Furthermore, the residual lignin content in LCNF-Mec aerogels showed a great improvement in the removal capacity, reaching rates higher than 80%, further improving the cost efficiency of the samples due to the reduction in chemical treatments.

Preparation and characterization of carrageenan-embedded lanthanum iron oxide nanocomposite for efficient removal of arsenite ions from water

Arsenic (As) contamination in drinking water has grown into a global concern in recent years, which demands the development of various As remediation approaches. In this study, a new magnetic nanocomposite, carrageenan-embedded LaFeO₃ nanoparticles (abbreviated as CA-LaFeNPs) was synthesized by a sol-gel process and used to remove arsenite [As(III)] from water. The synthesized magnetic adsorbent was characterized by powder XRD, SEM, FTIR, VSM, and TGA. The adsorbent gel, CA-LaFeNP was mainly with LaFeO₃ in nanoscale particles with a saturation magnetization of 13.33 emu g^-1 and could be easily separated from water with a simple hand-held magnet in 2 minutes. The adsorption outcomes of the CA-LaFeNPs could be finely interpreted by Langmuir, Freundlich, and Tempkin isotherm models. The Langmuir isotherm model appears to have good regression coefficients, and maximum adsorption capacity was estimated to be 91 mg g^-1 for CA-LaFeNPs at 27 °C and pH 7. The removal efficiency observed for CA-FeNPs was 91% up to the As(III) concentration of 700 mg L^-1, while it decreased to 85% when the As(III) concentration was above 1200 mg L^-1. This low-cost and environmentally-friendly magnetic nanocomposite, CA-LaFeNPs could be more appropriate for real-world applications and also a substitute for the traditional magnetic nanoparticles.

Fabrication of superparamagnetic adsorbent based on layered double hydroxide as effective nanoadsorbent for removal of Sb (III) from water samples

In this study, the superparamagnetic adsorbent as Fe@Mg‐Al LDH was synthesised by different methods with two steps for the removal of heavy metal ions from water samples. An easy, practical, economical, and replicable method was introduced to remove water contaminants, including heavy ions from aquatic environments. Moreover, the structure of superparamagnetic adsorbent was investigated by various methods including Fourier transform infrared spectroscopy, field emission scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, and vibrating sample magnetometer. For better separation, ethylenediaminetetraacetic acid ligand was used, forming a complex with antimony ions to create suitable conditions for the removal of these ions. Cadmium and antimony ions were studied by floatation in aqueous environments with this superparamagnetic adsorbent owing to effective factors such as pH, amount of superparamagnetic adsorbent, contact time, sample temperature, volume, and ligand concentration. The model of Freundlich, Langmuir, and Temkin isotherms was studied to qualitatively evaluate the adsorption of antimony ions by the superparamagnetic adsorbent. The value of loaded antimony metal ions with Fe@Mg‐Al LDH was resulted at 160.15 mg/g. The standard deviation value in this procedure was found at 7.92%. The desorption volume of antimony metal ions by the adsorbent was found to be 25 ml. The thermodynamic parameters as well as the effect of interfering ions were investigated by graphite furnace atomic absorption spectrometry.