Combining structurally ordered intermetallic nodes: Kinetic and isothermal studies for removal of malachite green and methyl orange with mechanistic aspects

Enhanced removal of methyl orange and malachite green using mesoporous TO@CTAB nanocomposite: Synthesis, characterization, optimization and real wastewater treatment efficiency

This study explores the synthesis of a novel titanium oxide-cetyltrimethylammonium bromide (TO@CTAB) nanocomposite for the effective removal of malachite green (MG) and methyl orange (MO) dyes. The optimization of the nanocomposite's performance was carried out using response surface methodology (RSM). The adsorption characteristics were further evaluated through isotherm models, kinetic studies and thermodynamic analyses. The mesoporous nature of TO@CTAB was confirmed through BET analysis, revealing a pore diameter of 4.625 nm. The crystalline size of TO@CTAB is 54.78 nm, and its crystalline index is 70.84%. The optimal operating conditions were established based on the results obtained from the ANOVA. The Langmuir isotherm model demonstrates superior adsorption performance compared to the Freundlich isotherm model, with adsorption efficiencies of 317.46 mg/g for MO and 306.748 mg/g for MG. The pseudo-second-order model, with an R2 value of 0.998 and 0.997 for MO and MG, respectively, provides a more accurate and reliable explanation of the adsorption process compared to the pseudo-first-order model. Furthermore, the high reusability and minimal deterioration of TO@CTAB were observed for up to 5 cycles. The analysis of the adsorption mechanism indicates that the adsorption of MG and MO occurs through H-bonding, electrostatic and π-π interactions. A comprehensive cost analysis of the process was conducted to evaluate the cost-effectiveness; total expenditure incurred during the process was determined to be within acceptable limits. TO@CTAB was assessed using real wastewater samples, demonstrating a decolourization efficiency of 82%. Additionally, it resulted in a reduction of COD, BOD, TSS and TDS.

Revolutionizing environmental cleanup: the evolution of MOFs as catalysts for pollution remediation

The global problem of ecological safety and public health necessitates, the development of new sustainable ideas for pollution remediation. In recent development, metal-organic frameworks (MOF) are the emerging technology with remarkable potential, which have been employed in environmental remediation. MOFs are networks that are created by the coordination of metals or polyanions with ligands and contain organic components that can be customized. The interesting features of MOFs are a large surface area, tuneable porosity, functional diversity, and high predictability of pollutant adsorption, catalysis, and degradation. It is a solid material that occupies a unique position in the war against environmental pollutants. One of the main benefits of MOFs is that they exhibit selective adsorption of a wide range of pollutants, including heavy metals, organics, greenhouse gases, water and soil. Only particles with the right combination of pore size and chemical composition will achieve this selectivity, derived from the high level of specificity. Besides, they possess high catalytic ability for the removal of pollutants by means of different methods such as photocatalysis, Fenton-like reactions, and oxidative degradation. By generating mobile active sites within the framework of MOFs, we can not only ensure high affinity for pollutants but also effective transformation of toxic chemicals into less harmful or even inert end products. However, the long-term stability of MOFs is becoming more important as eco-friendly parts are replaced with those that can be used repeatedly, and systems based on MOFs that can remove pollutants in more than one way are fabricated. MOFs can reduce waste production, energy consumption as compared to the other removal process. With its endless capacities, MOF technology brings a solution to the environmental cleansing problem, working as a flexible problem solver from one field to another. The investigation of MOF synthesis and principles will allow researchers to fully understand the potential of MOFs in environmental problem solving, making the world a better place for all of us.

Zeolites in wastewater treatment: A comprehensive review on scientometric analysis, adsorption mechanisms, and future prospects

Zeolites possess a microporous crystalline structure, a large surface area, and a uniform pore size. Natural or synthetic zeolites are commonly utilized for adsorbing organic and inorganic compounds from wastewater because of their unique physicochemical properties and cost-effectiveness. The present review work comprehensively revealed the application of zeolites in removing a diverse range of wastewater contaminates, such as dyes, heavy metal ions, and phenolic compounds, within the framework of contemporary research. The present review work offers a summary of the existing literature about the chemical composition of zeolites and their synthesis by different methods. Subsequently, the article provides a wide range of factors to examine the adsorption mechanisms of both inorganic and organic pollutants using natural zeolites and modified zeolites. This review explores the different mechanisms through which zeolites effectively eliminate pollutants from aquatic matrices. Additionally, this review explores that the Langmuir and pseudo-second-order models are the predominant models used in investigating isothermal and kinetic adsorption and also evaluates the research gap on zeolite through scientometric analysis. The prospective efficacy of zeolite materials in future wastewater treatment may be assessed by a comparative analysis of their capacity to adsorb toxic inorganic and organic contaminates from wastewater, with other adsorbents.

Facile synthesis of lignin-based Fe-MOF for fast adsorption of methyl orange

To rapidly remove dyes from wastewater, iron-based metal-organic frameworks modified with phenolated lignin (NH2-MIL@L) were prepared by a one-step hydrothermal method. Analyses of the chemical structure and adsorption mechanism of the NH2-MIL@L proved the successful introduction of lignin and the enhancement of its adsorption sites. Compared with NH2-MIL-101-Fe without phenolated lignin, the modification with lignin increased the methyl orange (MO) adsorption rate of NH2-MIL@L. For the best adsorbent, NH2-MIL@L4, the MO adsorption efficiency in MO solution reached 95.09% within 5 min. NH2-MIL@L4 reached adsorption equilibrium within 90 min, exhibiting an MO adsorption capacity of 195.31 mg/g. The process followed pseudo-second-order kinetics and the Dubinin-Radushkevich model. MO adsorption efficiency of NH2-MIL@L4 was maintained at 89.87% after six adsorption-desorption cycles. In mixed solutions of MO and methylene blue (MB), NH2-MIL@L4 achieved an MO adsorption of 94.02% at 5 min and reached MO adsorption equilibrium within 15 min with an MO adsorption capacity of 438.6 mg/g, while the MB adsorption equilibrium was established at 90 min with an MB adsorption rate and capacity of 95.60% and 481.34 mg/g, respectively. NH2-MIL@L4 sustained its excellent adsorption efficiency after six adsorption-desorption cycles (91.2% for MO and 93.4% for MB). The process of MO adsorption by NH2-MIL@L4 followed the Temkin model and pseudo-second-order kinetics, while MB adsorption followed the Dubinin-Radushkevich model and pseudo-second-order kinetics. Electrostatic interactions, π-π interactions, hydrogen bonding, and synergistic interactions affected the MO adsorption process of NH2-MIL@L4.

Isothermal and kinetic screening of methyl red and methyl orange dyes adsorption from water by Delonix regia biochar-sulfur oxide (DRB-SO)

In this study, Delonix regia seed pods (DRSPs) as a locally available material were refluxed in 90% H2SO4 to yield a novel D. regia seed pods biochar-sulfur oxide (DRB-SO). FTIR, BET, BJH, SEM, EDX, XRD, DSC and TGA were applied to investigate the characterizations of the prepared DRB-SO. Various adsorption parameters like pH effect, dye concentration effect, adsorbent dose, reaction time isotherm and kinetic study were carried out to explain the process of adsorption of methyl orange (MO) and methyl red (MR) onto DRB-SO. Langmuir's adsorption model perfectly explained the adsorption process onto the surface of DRB-SO as a monolayer. The maximum adsorption efficiency of DRB-SO was (98%) and (99.6%) for MO and MR respectively which attained after 150 min with an adsorbent dose of 0.75 g/L. The pseudo-second-order kinetic model best explained the process of adsorption of MO and MR dyes by DRB-SO. The highest observed adsorption amount was as high as 144.9 mg/g for MO dye and 285.7 mg/g for MR dye, comparable with other reported materials based on activated carbon materials. All of the outcomes signposted a prodigious perspective of the fabricated biochar composite material in wastewater treatment. Using the regenerating DRB-SO through an acid-base regeneration process, six cycles of adsorption/desorption were examined. Over the course of the cycles, there was a minor decrease in the adsorption and desorption processes. Also, it was revealed what the most plausible mechanism was for DRB-SO to absorb the ions of the MO and MR dyes.

A comparative study on the malachite green dye adsorption of chemically synthesized and green MgFe2O4 nanoparticles using gerbera floral waste extract

The situation of discharging a large amount of dyes from the textile industries has caused many adverse effects on human health and the ecosystems. Emerging bio-nanomaterials represent a new trend in efficient dye removal in aqueous media. Herein, we mention that MgFe2O4 bioprepared using gerbera extract has been successfully used to adsorb malachite green (MG) in water. A comparison was made to determine the dye removal efficiency between biogenic MgFe2O4 (MFOB) and chemical MgFe2O4 (MFOC). The spherical MFOB material exhibited a large surface area of 85.0 m2 g-1 and high crystallinity. The obtained outcomes showed that the highest adsorption capacity of MG dye was 584.49 mg g-1 at a MFOB dose of 0.05 g L-1 and MG concentration of 10 mg L-1. Higher correlation coefficients in the Langmuir isotherm suggested monolayer adsorption of MG. The Box-Behnken design and response surface method were established to optimize MG removal percentage under the conditions, i.e., initial MG concentration (10-30 mg L-1), adsorbent dose (0.02-0.08 g L-1), and pH of dye solution (6-8). MFOB had good reusability with high removal efficiencies after three continuous cycles. Post reuse, this adsorbent still showed excellent stability through the verification of their structural properties in comparison with fresh MFOB, showing potential for practical applications.

Recent advances and potential applications for metal-organic framework (MOFs) and MOFs-derived materials: Characterizations and antimicrobial activities

Microbial infections, particularly those caused by antibiotic-resistant pathogens, pose a critical global health threat. Metal-Organic Frameworks (MOFs), porous crystalline structures built from metal ions and organic linkers, initially developed for gas adsorption, have emerged as promising alternatives to traditional antibiotics. This review, covering research up to 2023, explores the potential of MOFs and MOF-based materials as broad-spectrum antimicrobial agents against bacteria, viruses, fungi, and even parasites. It delves into the historical context of antimicrobial agents, recent advancements in MOF research, and the diverse synthesis techniques employed for their production. Furthermore, the review comprehensively analyzes the mechanisms of action by which MOFs combat various microbial threats. By highlighting the vast potential of MOFs, their diverse synthesis methods, and their effectiveness against various pathogens, this study underscores their potential as a novel solution to the growing challenge of antibiotic resistance.

Nanomaterials for sustainable remediation: efficient removal of Rhodamine B and lead using greenly synthesized novel mesoporous ZnO@CTAB nanocomposite

This study explores the dual applications of a greenly synthesized ZnO@CTAB nanocomposite for the efficient remediation of Rhodamine B (RhB) and lead (Pb). The synthesis method involves a sustainable approach, emphasizing environmentally friendly practices. FT-IR, XRD, FESEM, zeta potential, and particle size analyzer (PSA), BET, and UV-VIS were used to physically characterize the zinc oxide and CTAB nanocomposite (ZnO@CTAB). The size and crystalline index of ZnO@CTAB are 77.941 nm and 63.56% respectively. The Zeta potential of ZnO@CTAB is about - 22.4 mV. The pore diameter of the ZnO@CTAB was 3.216 nm, and its total surface area was 97.42 m2/g. The mechanism of adsorption was investigated through pHZPC measurements. The nanocomposite's adsorption performance was systematically investigated through batch adsorption experiments. At pH 2, adsorbent dose of 0.025 g, and temperature 50 °C, ZnO@CTAB removed the most RhB, while at pH 6, adsorbent dose of 0.11 g, and temperature 60 °C, ZnO@CTAB removed the most Pb. With an adsorption efficiency of 214.59 mg/g and 128.86 mg/g for RhB and Pb, the Langmuir isotherm model outperforms the Freundlich isotherm model in terms of adsorption. The pseudo-2nd-order model with an R2 of 0.99 for both RhB and Pb offers a more convincing explanation of adsorption than the pseudo-1st-order model. The results demonstrated rapid adsorption kinetics and high adsorption capacities for RhB and Pb. Furthermore, there was minimal deterioration and a high reusability of ZnO@CTAB till 4 cycles were observed.

Preparation of cationic surfactant modified two-dimensional (2D) multi-layered Ti3C2Tx MXene for methyl orange removal from aqueous solution: Kinetic, equilibrium, and adsorption mechanisms

In this study, cetyltrimethylammonium bromide-modified multi-layered Ti3C2Tx MXene (CMM) was produced using a Ti3AlC2 precursor, and its capacity to remove the anionic dye, methyl orange (MO), was investigated in detail. An electrostatic combination between negatively charged Ti3C2Tx nanosheets and cationic surfactant solution (CTAB) produced this adsorbent. This triggered an exposure of the accessible active sites to further boost adsorption effectiveness by increasing the distance between the MXene nanosheets. Prepared adsorbents were characterized using some analytical techniques, including TGA, FESEM, EDX, FTIR, XRD, and N2 adsorption-desorption. Furthermore, some influencing parameters such as contact time, solution of pH, loading adsorbent, and initial dye concentration were evaluated, with findings showing that MO could adsorb CMM to its maximum capacity at an adsorbent dosage of 0.83 g/L, a contact time of 90 min, and a solution pH of 3. Adsorption results were found to be highly linked with both Langmuir isotherm (R2 = 0.9990) and the pseudo-second-order kinetic model (R2 = 0.9924). The maximum adsorption capacity of MO was obtained at approximately 213.00 mg/g. Also, hydrogen bonding, π-cation interactions, and electrostatic adsorption can all be implicated in the mechanism of MO adsorption on CMM. The fabricated CMM is presented as a prospective adsorbent for the removal of dyes from polluted water, demonstrating robust recyclability for up to the fifth iteration. All these outstanding properties indicate that cetyltrimethylammonium bromide-modified multi-layered Ti3C2Tx MXene can be considered as applicable adsorbents for textile pollutants.

Effective adsorption of amoxicillin by using UIO-66@ Cr-MIL-101 nanohybrid: isotherm, kinetic, thermodynamic, and optimization by central composite design

In this research, the amoxicillin (AMX) removal was studied on a prepared nanosorbent from MOFs. The aim of this research work is to prepare nanohybrids based on metal-organic frameworks (MOFs) as an efficient nanosorbent for the absorption of amoxicillin drug. In this study, UIO-66 nanoparticles (UIO-66 NPs) were prepared from Zirconium (Zr) metal and 1,4-benzene dicarboxylic acid (BDC). Then UIO-66@Cr-MIL-101 nanohybrid was synthesized by hydrothermal method. Structural and physicochemical properties of nanohybrid UIO-66@Cr-MIL-101 were characterized by different analyses such as X-ray diffraction analysis (XRD), fourier transform infrared spectrometer (FT-IR), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), transmission electron microscopy (TEM), therapeutic goods administration (TGA), and Brunauer-Emmett-Teller (BET). The effect of four fundamental variables effective on adsorption was optimized by the central composite response surface methodology (CCRSM). This parameters including loading percentage of Cr-MIL-101 NPs (10-30%), initial concentration of AMX (20-140 mg L-1), contact time (20-60 min), and pH (20-10). The removal percentage (Re%) of AMX equal to 99.50% was obtained under the following conditions: The loading value of 20% Wt%, the initial concentration of AMX 80 mg L-1, contact time 20 min, and pH = 6. Also, the experimental data were investigated with famous kinetic models and isotherms, and it was observed that AMX removal by nanohybrid is correlated with the PSO kinetic model and Langmuir isotherm.

Adsorption of methyl orange from aqueous solution with lignin-modified metal-organic frameworks: Selective adsorption and high adsorption capacity

The lignin-based metal-organic framework (UIO-g-NL) was prepared by a Schiff base reaction of aminated lignin and the zirconium cluster-based MOF (UIO-66-NH2) as an adsorbent of methyl orange (MO). The results showed that UIO-g-NL maintained the original crystal structure and aminated lignin was successfully introduced after functionalization. UIO-g-NL selectively adsorbed MO from a mixed solution 50 mg/L MO and 50 mg/L methylene blue (MB), with an adsorption efficiency of nearly 100%. In a mixed solution 250 mg/L MB and 250 mg/L MO, UIO-g-NL adsorbed both dyes with 1120.70 mg/g for MB and 961.54 mg/g for MO. Hydrogen bonding, π-π and NH-π interactions, and electrostatic attraction contribute to the MO adsorption by UIO-g-NL. In the MO/MB mixture, MO adsorption by UIO-g-NL follows the pseudo-second-order kinetic and Freundlich isotherm models, which is an endothermic, spontaneous, and feasible adsorption process. Furthermore, the MO adsorption efficiency of UIO-g-NL remained high (>90%) after six re-use cycles.

Network-Polymer-Modified Superparamagnetic Magnetic Silica Nanoparticles for the Adsorption and Regeneration of Heavy Metal Ions

Superparamagnetic magnetic nanoparticles (MNPs, Fe3O4) were first synthesized based on a chemical co-precipitation method, and the core-shell magnetic silica nanoparticles (MSNPs, Fe3O4@SiO2) were obtained via hydrolysis and the condensation of tetraethyl orthosilicate onto Fe3O4 seed using a sol-gel process. Following that, MSNPs were immobilized using a three-step grafting strategy, where 8-hloroacetyl-aminoquinoline (CAAQ) was employed as a metal ion affinity ligand for trapping specific heavy metal ions, and a macromolecular polymer (polyethylenimine (PEI)) was selected as a bridge between the surface hydroxyl group and CAAQ to fabricate a network of organic networks onto the MSNPs' surface. The as-synthesized MSNPs-CAAQ nanocomposites possessed abundant active functional groups and thus contained excellent removal features for heavy metal ions. Specifically, the maximum adsorption capacities at room temperature and without adjusting pH were 324.7, 306.8, and 293.3 mg/g for Fe3+, Cu2+, and Cr3+ ions, respectively, according to Langmuir linear fitting. The adsorption-desorption experiment results indicated that Na2EDTA proved to be more suitable as a desorbing agent for Cr3+ desorption on the MSNPs-CAAQ surface than HCl and HNO3. MSNPs-CAAQ exhibited a satisfactory adsorption capacity toward Cr3+ ions even after six consecutive adsorption-desorption cycles; the adsorption efficiency for Cr3+ ions was still 88.8% with 0.1 mol/L Na2EDTA as the desorbing agent. Furthermore, the MSNPs-CAAQ nanosorbent displayed a strong magnetic response with a saturated magnetization of 24.0 emu/g, and they could be easily separated from the aqueous medium under the attraction of a magnet, which could facilitate the sustainable removal of Cr3+ ions in practical applications.

Lignin-modified metal-organic framework as an effective adsorbent for the removal of methyl orange

Herein, lignin-modified metal-organic frameworks (NH2-UIO@L) are prepared using a one-step synthesis as sorbents for the removal of organic dyes from water. The introduction of lignin improved the adsorption sites. NH2-UIO@L2 adsorption of MO conforms to Langmuir model, and the adsorption capacity of NH2-UIO@L2 on MO was 214.13 mg·L-1 with an adsorption efficiency up to 99.28 %, which was significantly higher than values for other adsorbents. Due to hydrogen bonds, π-π interactions and electrostatic interactions, MO was effectively removed by NH2-UIO@L2 and its adsorption efficiency is maintained at 90.55 % after six cycles. The adsorption kinetics showed that the NH2-UIO@L2 adsorption of MO was chemical adsorption and controlled by intraparticle diffusion and external mass transfer. Further, the adsorption performance of NH2-UIO@L2 on MO and MB in mixed MO/MB solution was investigated. The adsorption capacity of NH2-UIO@L2 in mixed MO/MB solution was 207.04 mg·L-1 for MO and 243.31 mg·L-1 for MB; the adsorption of NH2-UIO@L2 on MO followed the Dubinin-Radushkevich and pseudo-second-order models, and the adsorption on MB followed the Temkin and pseudo-second-order models. Hydrogen bonds, π-π interactions, and pore filling are all implicated in the removal of MO and MB. In particular, the electrostatic attraction between MB and MO improves the adsorption efficiency of NH2-UIO@L2 on MB. NH2-UIO@L2 has good reusability, maintaining an adsorption efficiency of 97.66 % for MO and up to 99.15 % for MB after six cycles. Its simple preparation and superior adsorption suggest that NH2-UIO@L2 has considerable potential to remove organic dyes from wastewater.

Sustainable approach for adsorptive removal of cationic and anionic dyes by titanium oxide nanoparticles synthesized biogenically using algal extract ofSpirulina

Worldwide, dyes are significant pollutants present in water because of their huge consumption for industrial purposes. These dyes as pollutants cause serious health issues in human beings and cause the loss of aquatic biodiversity. So, remediation of pollutants like dyes from wastewater is the need of the hour. In the present study, we greenly synthesizedSpirulina-mediated titanium oxide nanoparticles (STONPs) for the adsorptive remediation of methyl orange (MO) (anionic) and malachite green (MG) (cationic) dyes. The characterization of STONPs was performed by Field emission scanning electron microscopy (FESEM) with EDX, FT-IR, XRD, Zeta Potential and particle size analyzer, Raman spectroscopy, and UV-vis. The various parameter effects like pH, nano-adsorbent dose, the concentration of dye, contact time, and temperature were also examined. Adsorption isotherms like Langmuir, Freundlich, and Temkin, and Kinetics models like Elovich Model, Pseudo 1st, intraparticle diffusion model (IPDM), Pseudo 2nd order, and the thermodynamic model were applied for a stronger interpretation. Theqmaxattained utilizing the Langmuir adsorption model was 272.4795 mg g-1and 209.6436 mg g-1for MO and MG correspondingly. The regeneration study of synthesized nanomaterials up to five cycles was also done. We found that greenly synthesized STONPs have great potential for adsorptive remediation for both MG and MO dyes.

Sonocrystallization of a novel ZIF/zeolite composite adsorbent with high chemical stability for removal of the pharmaceutical pollutant azithromycin from contaminated water

Water pollution management, reduction, and elimination are critical challenges of the current era that threaten millions of lives. By spreading the coronavirus in December 2019, the use of antibiotics, such as azithromycin increased. This drug was not metabolized, and entered the surface waters. ZIF-8/Zeolit composite was made by the sonochemical method. Furthermore, the effect of pH, the regeneration of adsorbents, kinetics, isotherms, and thermodynamics were attended. The adsorption capacity of zeolite, ZIF-8, and the composite ZIF-8/Zeolite were 22.37, 235.3, and 131 mg/g, respectively. The adsorbent reaches the equilibrium in 60 min, and at pH = 8. The adsorption process was spontaneous, endothermic associated with increased entropy. The results of the experiment were analyzed using Langmuir isotherms and pseudo-second order kinetic models with a R2 of 0.99, and successfully removing the composite by 85% in 10 cycles. It indicated that the maximum amount of drug could be removed with a small amount of composite.

Pyrolyzed magnetic NiO/carbon-derived nanocomposite from a hierarchical nickel-based metal-organic framework with ultrahigh adsorption capacity

Herein, a simple one-pot solvothermal approach is used to create magnetic porous carbon nanocomposites which obtained from a nickel-based metal-organic framework (Ni-MOF) and examined for their ability to uptake methyl orange (MO) dye. Derived carbons with exceptional porosity and magnetic properties were created during the different pyrolysis temperatures of Ni-MOF (700, 800, and 900 °C) under a nitrogen atmosphere. The black powders were given the names CDM-700, CDM-800, and CDM-900 after they were obtained. A variety of analysis methods, including FESEM, EDS, XRD, FTIR, VSM, and N₂ adsorption-desorption were used to characterize as-prepared powders. Furthermore, adsorbent dosage, contact time, pH variation, and initial dye concentration effects was investigated. The maximum adsorption capacities were 307.38, 5976.35, 4992.39, and 2636.54 mg/g for Ni-MOF, CDM-700, CDM-800, and CDM-900, respectively, which show the ultrahigh capacity of the resulted nanocomposites compared to newest materials. The results showed that not only the crystallinity turned but also the specific surface area was increased about four times after paralyzing. The results showed that the maximum adsorption capacity of MO dye for CDM-700 was obtained at adsorbent dosage of 0.083 g/L, contact time of 60 min, feed pH of 3, and temperature of 45 °C. The Langmuir model has the best match and suggests the adsorption process as a single layer. According to the results of reaction kinetic studies using well-known models, the pseudo-second-order model (R² = 0.9989) displayed high agreement with the experimental data. The synthesized nanocomposite is introduced as a promising superadsorbent for eliminating dyes from contaminated water due to strong recycling performance up to the fifth cycle.

Textural properties and adsorption behavior of Zn-Mg-Al layered double hydroxide upon crystal violet dye removal as a low cost, effective, and recyclable adsorbent

The preparation of adsorbents plays a vital role in the adsorption method. In particular, many adsorbents with high specific surface areas and unique shapes are essential for the adsorption strategy. A Zn-Mg-Al/layer double hydroxide (LDH) was designed in this study using a simple co-precipitation process. Adsorbent based on Zn-Mg-Al/LDH was used to remove crystal violet (CV) from the wastewater. The impacts of the initial dye concentration, pH, and temperature on CV adsorption performance were systematically examined. The adsorbents were analyzed both before and after adsorption using FTIR, XRD, and SEM. The roughness parameters and surface morphologies of the produced LDH were estimated using 3D SEM images. Under the best conditions (dose of adsorbent = 0.07 g and pH = 9), the maximum adsorption capacity has been achieved. Adsorption kinetics studies revealed that the reaction that led to the adsorption of CV dye onto Zn-Mg-Al/LDH was a pseudo-second-order model. Additionally, intraparticle diffusion suggests that Zn-Mg-Al/LDH has a fast diffusion constant for CV molecules (0.251 mg/(g min^1/2)). Furthermore, as predicted by the Langmuir model, the maximal Zn-Mg-Al/LDH adsorption capacity of CV was 64.80 mg/g. The CV dimensionless separation factor (R_L) onto Zn-Mg-Al/LDH was 0.769, indicating that adsorption was favorable. The effect of temperature was performed at 25, 35, and 45 °C in order to establish the thermodynamic parameters ∆H^o, ∆S^o, and ∆G^o. The computed values indicated exothermic and spontaneous adsorption processes. The study presented here might be used to develop new adsorbents with enhanced adsorption capabilities for the purpose of protecting the water environment.

Effective and Efficient Porous CeO2 Adsorbent for Acid Orange 7 Adsorption

A porous CeO₂ was synthesized following the addition of guanidine carbonate to a Ce³⁺ aqueous solution, the subsequent addition of hydrogen peroxide and a final hydrothermal treatment. The optimal experimental parameters for the synthesis of porous CeO₂, including the amounts of guanidine carbonate and hydrogen peroxide and the hydrothermal conditions, were determined by taking the adsorption efficiency of acid orange 7 (AO7) dye as the evaluation. A template-free hydrothermal strategy could avoid the use of soft or hard templates and the subsequent tedious procedures of eliminating templates, which aligned with the goals of energy conservation and emission reduction. Moreover, both the guanidine carbonate and hydrogen peroxide used in this work were accessible and eco-friendly raw materials. The porous CeO₂ possessed rapid adsorption capacities for AO7 dye. When the initial concentration of AO7 was less than 130 mg/L, removal efficiencies greater than 90.0% were obtained, achieving a maximum value of 97.5% at [AO7] = 100 mg/L and [CeO₂] = 2.0 g/L in the first 10 min of contact. Moreover, the adsorption-desorption equilibrium between the porous CeO₂ adsorbent and the AO7 molecule was basically established within the first 30 min. The saturated adsorption amount of AO7 dye was 90.3 mg/g based on a Langmuir linear fitting of the experimental data. Moreover, the porous CeO₂ could be recycled using a NaOH aqueous solution, and the adsorption efficiency of AO7 dye still remained above 92.5% after five cycles. This study provided an alternative porous adsorbent for the purification of dye wastewater, and a template-free hydrothermal strategy was developed to enable the design of CeO₂-based catalysts or catalyst carriers.

Chitin-Based Magnesium Oxide Biocomposite for the Removal of Methyl Orange from Water

In this work, a cost-effective chitin-based magnesium oxide (CHt@MgO) biocomposite with excellent anionic methyl orange (MO) dye removal efficiency from water was developed. The CHt@MgO biocomposite was characterized by FT-IR, XRD, SEM-EDX, and TGA/DTG. Results proved the successful synthesis of CHt@MgO biocomposite. Adsorption of MO on the CHt@MgO biocomposite was optimized by varying experimental conditions such as pH, amount of adsorbent (m), contact time (t), temperature (T), and initial MO concentration (C_o). The optimized parameters for MO removal by CHt@MgO biocomposite were as follows: pH, 6; m, 2 g/L; t, 120 min. Two common isotherm models (Langmuir and Freundlich) and three kinetic models (pseudo-first-order (PFO), pseudo-second-order (PSO), and intraparticle diffusion (IPD)) were tested for experimental data fitting. Results showed that Langmuir and PFO were the most suitable to respectively describe equilibrium and kinetic results on the adsorption of MO adsorption on CHt@MgO biocomposite. The maximum Langmuir monolayer adsorption capacity (q_m) on CHt@MgO biocomposite toward MO dye was 252 mg/g at 60 °C. The reusability tests revealed that CHt@MgO biocomposite possessed high (90.7%) removal efficiency after the fifth regeneration cycle.

Regulation of Structure and Anion-Exchange Performance of Layered Double Hydroxide: Function of the Metal Cation Composition of a Brucite-like Layer

As anion-exchange materials, layered double hydroxides (LDHs) have attracted increasing attention in the fields of selective adsorption and separation, controlled drug release, and environmental remediation. The metal cation composition of the laminate is the essential factor that determines the anion-exchange performance of LDHs. Herein, we review the regulating effects of the metal cation composition on the anion-exchange properties and LDH structure. Specifically, the internal factors affecting the anion-exchange performance of LDHs were analyzed and summarized. These include the intercalation driving force, interlayer domain environment, and LDH morphology, which significantly affect the anion selectivity, anion-exchange capacity, and anion arrangement. By changing the species, valence state, size, and mole ratio of the metal cations, the structural characteristics, charge density, and interlayer spacing of LDHs can be adjusted, which affect the anion-exchange performance of LDHs. The present challenges and future prospects of LDHs are also discussed. To the best of our knowledge, this is the first review to summarize the essential relationship between the metal ion composition and anion-exchange performance of laminates, providing important insights for regulating the anion-exchange performance of LDHs.

ZIF-8 metal organic framework materials as a superb platform for the removal and photocatalytic degradation of organic pollutants: a review

Metal organic frameworks (MOFs) are attracting significant attention for applications including adsorption, chemical sensing, gas separation, photocatalysis, electrocatalysis and catalysis. In particular, zeolitic imidazolate framework 8 (ZIF-8), which is composed of zinc ions and imidazolate ligands, have been applied in different areas of catalysis due to its outstanding structural and textural properties. It possesses a highly porous structure and chemical and thermal stability under varying reaction conditions. When used alone in the reaction medium, the ZIF-8 particles tend to agglomerate, which inhibits their removal efficiency and selectivity. This results in their mediocre reusability and separation from aqueous conditions. Thus, to overcome these drawbacks, several well-designed ZIF-8 structures have emerged by forming composites and heterostructures and doping. This review focuses on the recent advances on the use of ZIF-8 structures (doping, composites, heterostructures, etc.) in the removal and photodegradation of persistent organic pollutants. We focus on the adsorption and photocatalysis of three main organic pollutants (methylene blue, rhodamine B, and malachite green). Finally, the key challenges, prospects and future directions are outlined to give insights into game-changing breakthroughs in this area.

Green synthesis of Mn3O4 nanoparticles using Costus woodsonii flowers extract for effective removal of malachite green dye

The pollution of organic dyes such as malachite green is one of the globally critical issues, calling for efficient mitigation methods. Herein, we developed green Mn₃O₄ nanoparticles synthesized using natural compounds extracted from Costus woodsonii flowers under an ultrasound-assisted mode. The materials were characterized using several physicochemical techniques such as Fourier-transform infrared spectroscopy, X-ray diffraction, Energy-dispersive X-ray spectroscopy, scanning electron microscopy, Raman spectroscopy, and N₂ adsorption desorption isotherm measurement. The X-ray diffraction and N₂ isotherm plots confirmed the presence of tetragonal γ-Mn₃O₄ phase and mesoporous structure, respectively. Carbonyl groups derived from flavonoids or carboxylic compounds were found in the surface of green Mn₃O₄ nanoparticles. The effect of pH, contact time, dose, and concentration on the adsorption of malachite green over green Mn₃O₄ was carried out. The maximum malachite green adsorption capacity for green Mn₃O₄ nanoparticles was 101-162 mg g^-1. Moreover, kinetic and isotherm adsorption of malachite green obeyed Langmuir (R_adj.² = 0.980-0.995) and pseudo first-order models (R_adj.² = 0.996-1.00), respectively. Adsorption of malachite green over green Mn₃O₄ was a thermodynamically spontaneous process due to negative Gibbs free energy values (ΔG^ο < 0). Green Mn₃O₄ nanoparticles offered a high stability through the FR-IR spectra analysis. With a good recyclability of 4 cycles, green Mn₃O₄ nanoparticles can be used as potential adsorbent for removing malachite green dye from water.

Rational synthesis and characterization of highly water stable MOF@GO composite for efficient removal of mercury (Hg2+) from water

The present study is aimed at adsorptive removal of Mercury (Hg²⁺) using highly functionalized nanomaterials based on Graphene Oxide Zeolitic Imidazolate Framework composite (ZIF-67@GO). Solvothermal methodology was used to synthesize ZIF-67@GO composite. Synthesized compounds were confirmed by FTIR, SEM, PXRD and EDX analysis. The as-prepared ZIF-67@GO was tested as efficient adsorbent for effective removal of Mercury (Hg²⁺) from aquatic environment. The atomic adsorption spectrophotometer was used to monitor the process of adsorption of Hg⁺² on ZIF-67@GO. From the adsorption data, the maximum removal efficiency achieved was 91.1% using 10 mg amount of composite for 50 mL using 20 ppm Mercury (Hg²⁺) solution. Different parameters like pH, contact time, concentration, adsorption kinetics and isotherm were also examined to explore adsorption process. Adsorption data fitted well for Freundlich Model having R² value of 0.9925 than Langmuir Isotherm with R² value of 0.9238. Kinetics were rapid and excellently described via 2nd order model with R² = 0.99946 than 1st order model with R² value of 0.8836. Freundlich and pseudo 2nd order models validated that multilayer chemisorption occurs during adsorption process due to the presence of highly functionalized sites on ZIF-67@GO composite. The synthesized composite material has shown excellent reusability. Thus, water stable ZIF-67@GO composites can efficiently be used for Mercury (Hg²⁺) confiscation from water.

Insights into a new alternative method with graphene oxide/polyacrylamide/Fe3O4 nanocomposite for the extraction of six odor-active esters from Strong-aroma types of Baijiu

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A novel approach of MSPE-GC/MS based on GO/PAM/Fe₃O₄ was developed for odor-active esters determination in Baijiu samples.

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GO/PAM/Fe₃O₄ earned highly selective recognition properties and larger adsorption capacities for six odor-active esters.

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The method provided lower LODs, better precision and faster separation.

Liquid-liquid extraction (LLE) is the most commonly utilized technique for the extraction of odor-active esters (OAEs) in strong-aroma types of Baijiu (SAB). However, since the contents of different OAEs in SAB vary widely, it is still a puzzle to ensure that all OAEs to be thoroughly extracted by LLE without the problem of saturated adsorption. Herein, a novel approach of magnetic solid phase extraction (MSPE), based on the magnetic graphene oxide nanocomposite modified with polyacrylamide (GO/PAM/Fe₃O₄), was employed for the efficient extraction of six OAEs from SAB. Compared with LLE, GO/PAM/Fe₃O₄ exhibited highly selective recognition properties and larger adsorption capacities for OAEs (ranging from 13.68 to 39.06 mg/g), resulting in better extraction performances for OAEs. Coupled with GC–MS, six OAEs in real SAB were successfully determined, with recoveries ranged from 70.1 ∼ 90.0% and LODs at 0.08 ∼ 1.35 µg/L. Overall, the MSPE-GC/MS is a promising alternative for accurate determination of OAEs in SAB.

Strategic combination of metal-organic frameworks and C3N4 for expeditious photocatalytic degradation of dye pollutants

The potential of fabricated silver and bismuth Co-N-doped imidazolate embedded into graphitic nitride BiO-Ag(0)/C₃N₄@ZIF-67 for the degradation of Methylene blue (MB) and Congo red (CR) dyes have been reported. The synthesized materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy photoluminescence (PL) spectroscopy, and electrochemical impedance spectroscopy (EIS). The band gaps of ZIF-67, C₃N₄ and composites were calculated using Tauc plot. Besides, it was revealed that incorporation of silver, bismuth, and C₃N₄ reduced the band gap energy to 2.2 eV. The introduction of metallic species in the precursors promoted better charge separation behavior towards photogenerated electron and hole in the heterojunction composite. Two perilous organic dyes; MB and CR were degraded under natural sunlight irradiation. The photocatalytic efficiency of BiO-Ag(0)/C₃N₄@ZIF-67 for the removal of CR and MB significantly increased compared to bare ZIF-67. The enhanced photocatalytic activity of BiO-Ag(0)/C₃N₄@ZIF-67 is attributed to the higher surface area and Plasmon effect of noble silver metal. The solar light-triggered degradation of MB and CR yielded efficient efficiency of 96.5 and 90% for 10 mg/L of dye solution each. Additionally, the effect of pH was evaluated for optimizing degradation of CR and MB dyes. The kinetics studies of both CR and MB were clarified according to Langmuir model. The reusability and quenching investigation of active species were carried out to discover find catalytic potential of the composite. Besides, possible dye degradation mechanism was proposed for BiO-Ag(0)/C₃N₄@ZIF-67. The obtained results indicated that solar-light triggered photocatalyst BiO-Ag(0)/C₃N₄@ZIF-67 can be employed as a promising approach for photocatalytic elimination of organic pollutants.

Metal-Organic Frameworks Derived Electrocatalysts for Oxygen and Carbon Dioxide Reduction Reaction

The increasing demands of energy and environmental concerns have motivated researchers to cultivate renewable energy resources for replacing conventional fossil fuels. The modern energy conversion and storage devices required high efficient and stable electrocatalysts to fulfil the market demands. In previous years, we are witness for considerable developments of scientific attention in Metal-organic Frameworks (MOFs) and their derived nanomaterials in electrocatalysis. In current review article, we have discussed the progress of optimistic strategies and approaches for the manufacturing of MOF-derived functional materials and their presentation as electrocatalysts for significant energy related reactions. MOFs functioning as a self-sacrificing template bid different benefits for the preparation of metal nanostructures, metal oxides and carbon-abundant materials promoting through the porous structure, organic functionalities, abundance of metal sites and large surface area. Thorough study for the recent advancement in the MOF-derived materials, metal-coordinated N-doped carbons with single-atom active sites are emerging candidates for future commercial applications. However, there are some tasks that should be addressed, to attain improved, appreciative and controlled structural parameters for catalytic and chemical behavior.

Synthesis of MgAl-LDH@ZIF-8 composites by in situ growth method for highly efficient phosphate removal

Removal of phosphate from wastewater by adsorption has become one of the effective ways to mitigate the negative effects of eutrophication in water bodies, and efficient adsorbent is the key....

RSM, ANN-GA and ANN-PSO modeling of SDBS removal from greywater in rural areas via Fe2O3-coated volcanic rocks

Decontamination and reuse of greywater in rural areas has attracted increasing attention. Typical contaminants in grey water are SDBS, which has a stubborn molecular structure. In this study, Fe₂O₃-coated volcanic rocks (Fe₂O₃-VR) prepared from FeCl₃ solution by a heating evaporation method can reach 95% removal of SDBS, which is 80% higher than before. The effect of contact time, pH, initial concentration, FeCl₃ solution concentration, adsorbent dosage and calcination temperature on the removal rate was researched and modeled by response methodology (RSM) and artificial neural network (ANN). Based on the univariate test, the Box-Behnken design method was used to establish the data sample, which represented a quadratic polynomial model with p-value <0.001, R² = 0.9872, while the ANN model has the better performance with R² = 0.9961. The weights of the BP-ANN model were further analyzed using the Garson equation, and the results showed that the validity ranking of the variables was as follows: contact time (37.31%) > calcination temperature (29.43%) > dosage (24.44%) > initial concentration (17.18%) > FeCl₃ solution concentration (17.18%) > pH (11.56%). Genetic algorithm (GA) and particle swarm optimization (PSO) were selected to optimize the process parameters. The results showed that ANN-PSO methodology presented a satisfactory alternative and the predicted removal efficiency was 99.9982% with relative error = 0.2230. The optimum level of contact time, pH, initial SDBS concentration, FeCl₃ solution concentration, adsorbent dosage and calcination temperature is 136.45 min, 5.64, 22.4 mg L⁻¹, 0.3 mol L⁻¹, 83.21 g L⁻¹, 274.02 °C, respectively. Moreover, Fe₂O₃-VR was characterized via instrumental analyses (SEM-EDS, FTIR, XRD, BET).

This paper provides a new method for SDBS removal and parameter optimization of the adsorption process using RSM and ANN models.

Dynamic experiment on the treatment of acidic chromium-containing wastewater by lignite loaded nano FeS

In terms of the problem of severe pollution to the ecological environment caused by the acidic chrome-containing wastewater produced in the tanning, electroplating, metallurgy, printing and dyeing and other industries, based on the good adsorbability, reducibility and other properties of heavy metals such as Cr(vi) by lignite and nano FeS, the lignite-loaded nano FeS adsorbing material (nFeS-lignite) was prepared by ultrasonic precipitation method. NFeS-lignite and lignite were used as fillers to construct 1# and 2# dynamic columns to carry out the dynamic treatment experiment of acidic chrome-containing wastewater. And nFeS-lignite and lignite were characterized by XRD, SEM and EDS to explore the regularity, long-acting properties and removal mechanism of acidic chrome-containing wastewater treated by NFeS-lignite and lignite. The results indicate that: ① during 25 days of operation, the average removal percentages of Cr(vi) in the 1# and 2# dynamic columns are 71.6% and 53.1%. The average removal percentages of total chromium in 1# and 2# dynamic columns are 54.4% and 28.8%, and the average effluent pH of 1# and 2# dynamic columns is 5.3 and 7.3. ② According to XRD, SEM, EDS and FTIR analysis, the reducing groups in the structure of nFeS-lignite, such as –CH₃, –CH₂, C–O and Ar-OH, participate in the reaction and are oxidized to C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> C, CO and other groups. A large number of sediment crystals appeared on the particle surface, and new diffraction peaks such as FeOOH, Cr(OH)₃ and Cr₂S₃ appeared at the same time, indicating that after Cr(vi) was reduced to Cr(iii), it would be fixed on the surface of nFeS-lignite in the form of precipitation such as hydroxide and sulfide.

Based on the good adsorption and reducibility of Cr(vi) of lignite and nano-FeS, the lignite supported nano-FeS adsorption material (nFeS-lignite) was prepared by ultrasonic precipitation method to treat acidic chromium-containing wastewater.

Recent Advances in Synthesis and Applications of Single-Atom Catalysts for Rechargeable Batteries

The rapid development of flexible and wearable optoelectronic devices, demanding the superior, reliable, and ultra-long cycling energy storage systems. But poor performances of electrode materials used in energy devices are main obstacles. Recently, single-atom catalysts (SACs) are considered as emerging and potential candidates as electrode materials for battery devices. Herein, we have discussed the recent methods for the fabrication of SACs for rechargeable metal-air batteries, metal-CO₂ batteries, metal-sulfur batteries, and other batteries, following the recent advances in assembling and performance of these batteries by using SACs as electrode materials. The role of SACs to solve the bottle-neck problems of these energy storage devices and future perspectives are also discussed.

Organic Dyes versus Adsorption Processing

Even in the first quarter of the XXI century, the presence of organic dyes in wastewaters was a normal occurrence in a series of countries. As these compounds are toxic, their removal from these waters is a necessity. Among the separation technologies, adsorption processing appeared as one of the most widely used to reach this goal. The present work reviewed the most recent approaches (first half of the 2021 year) regarding the use of a variety of adsorbents in the removal of a variety of organic dyes of different natures.