Hierarchical mesoporous ZIF-67@LDH for efficient adsorption of aqueous Methyl Orange and Alizarine Red S

Magnetic CoFe hydrotalcite composite Co metal-organic framework material efficiently activating peroxymonosulfate to degrade sulfamethoxazole: Oxygen vacancy-mediated radical and non-radical pathways

Herein, a novel rich oxygen vacancy (Ov) cobalt-iron hydrotalcite composite cobalt metal-organic framework material (ZIF-67/CoFe-LDH) was prepared by simple urea water and heat reduction approach and utilized for the peroxymonosulfate (PMS) system to remove sulfamethoxazole (SMX). 95 ± 1.32 % SMX (20 mg/L) was able to degraded in 20 min with TOC removal of 53 ± 1.56 % in ZIF-67/CoFe-LDH/PMS system. The system maintained a fantastic catalytic capability with wide pH range (3-9) and common interfering substances (Cl-, NO3-, CO32-, PO42- and humic acid (HA)), and the degradation efficiency could even remain 80.2 ± 1.48 % at the fifth cycle. Meanwhile, the applicability and feasibility of the catalysts for practical water treatment was verified by the degradation effects of SMX in different water environments and several other typical pollutants. Co and Fe bimetallic active centers synergistically activate PMS, and density functional theory (DFT) predicted adsorption energy about Ov in ZIF-67/CoFe-LDH for PMS was 1.335 eV, and OO bond length of PMS was stretched to 1.826 Å. As a result, PMS was more easily activated and broken, which accelerated the singlet oxygen (1O2), sulfate radical (SO4•-), high-valent metals and other reactive oxygen species (ROS). Radical and non-radical jointly degrading the pollutants improved the catalytic effect. Finally, SMX degradation intermediates were analyzed to explain the degradation pathway and their biotoxicity was also evaluated. This paper provides a new research perspective of oxygen vacancy activating PMS to degrade pollutants.

Preparation and modification of polymer microspheres, application in wastewater treatment: A review

The removal of various pollutants from water is necessary due to the increasing requirements for the removal of various pollutants from wastewater and the quality of drinking water. Polymer microspheres are regarded as exemplary adsorbent materials due to their high adsorption efficiency, excellent adsorption performance, and ease of handling. Herein, the advantages and disadvantages of different preparation methods, modifications, applications and the current research status of polymer microspheres are summarized at large. Furthermore, the enhanced performance of modified composite microspheres is emphasized, including adsorption efficiency, thermal stability, and significant improvements in physical and chemical properties. Subsequently, the current applications and potential of polymeric microspheres for wastewater treatment, including the removal of inorganic and organic pollutants, heavy metal ions, and other contaminants are summarized. Finally, future research directions for polymer microspheres are proposed, outlining the challenges and solutions associated with the application of polymer microspheres in wastewater treatment.

Progress in layered double hydroxides (LDHs): Synthesis and application in adsorption, catalysis and photoreduction

Layered double hydroxides (LDHs), also known as anionic clays, have attracted significant attention in energy and environmental applications due to their exceptional physicochemical properties. These materials possess a unique structure with surface hydroxyl groups, tunable properties, and high stability, making them highly desirable. In this review, the synthesis and functionalization of LDHs have been explored including co-precipitation and hydrothermal methods. Furthermore, extensive research on LDH application in toxic pollutant removal has shown that modifying or functionalizing LDHs using materials such as activated carbon, polymers, and inorganics is crucial for achieving efficient pollutant adsorption, improved cyclic performance, as well as effective catalytic oxidation of organics and photoreduction. This study offers a comprehensive overview of the progress made in the field of LDHs and LDH-based composites for water and wastewater treatment. It critically discusses and explains both direct and indirect synthesis and modification techniques, highlighting their advantages and disadvantages. Additionally, this review critically discusses and explains the potential of LDH-based composites as absorbents. Importantly, it focuses on the capability of LDH and LDH-based composites in heterogeneous catalysis, including the Fenton reaction, Fenton-like reactions, photocatalysis, and photoreduction, for the removal of organic dyes, organic micropollutants, and heavy metals. The mechanisms involved in pollutant removal, such as adsorption, electrostatic interaction, complexation, and degradation, are thoroughly explained. Finally, this study outlines future research directions in the field.

Recent trends in wastewater treatment by using metal-organic frameworks (MOFs) and their composites: A critical view-point

Respecting the basic need of clean and safe water on earth for every individual, it is necessary to take auspicious steps for waste-water treatment. Recently, metal-organic frameworks (MOFs) are considered as promising material because of their intrinsic features including the porosity and high surface area. Further, structural tunability of MOFs by following the principles of reticular chemistry, the MOFs can be functionalized for the high adsorption performance as well as adsorptive removal of target materials. However, there are still some major concerns associated with MOFs limiting their commercialization as promising adsorbents for waste-water treatment. The cost, toxicity and regenerability are the major issues to be addressed for MOFs to get insightful results. In this article, we have concise the current strategies to enhance the adsorption capacity of MOFs during the water-treatment for the removal of toxic dyes, pharmaceuticals, and heavy metals. Further, we have also discussed the role of metallic nodes, linkers and associated functional groups for effective removal of toxic water pollutants. In addition to conformist overview, we have critically analyzed the MOFs as adsorbents in terms of toxicity, cost and regenerability. These factors are utmost important to address before commercialization of MOFs as adsorbents for water-treatment. Finally, some future perspectives are discussed to give directions for potential research.

Adsorption of tetracycline from aqueous solution by ZIF-8: Isotherms, kinetics and thermodynamics

In this study, ZIF-8 nanoparticles were synthesized using a simple method at room temperature. The ZIF-8 nanoparticles were then characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), BET (Brunauer-Emmett-Teller) specific surface area, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA) and zeta potential. Subsequent batch adsorption experiments evaluated the adsorption performance of ZIF-8 on tetracycline, examining key pa-rameters like reaction time, pH, temperature, and adsorbent dosage. The results revealed a removal rate for TC of up to 90.59%. The adsorption data aligned with the Sips model, showcasing a maximum adsorption capacity of 359.61 mg/g at 303K. Further, the adsorption kinetics adhered to the pseudo-second-order kinetic model with an equilibrium adsorption capacity of 90 mg/g at 303K. The considerable specific surface area of ZIF-8, standing at 1674.169 m2/g, likely enhances the adsorption efficacy. Analysis using XRD and FTIR confirmed the adsorption of TC on the ma-terial's surface. Overall, the predominant driving forces behind the adsorption process were identified as electrostatic interactions and π-π stacking interactions.

Synergistic approach for synthesis of functionalized biochar for efficient adsorption of Lopinavir from polluted water

The COVID-19 pandemic has led to a significant increase in antibiotic consumption, along with a 70% rise in antiviral drug concentrations in aquatic ecosystems. For the effective adsorption of antibiotics, biochar was modified by incorporating layered double hydroxide (LDH) through hydrothermal method. The results showed that LDH provides additional hydroxyl groups, positive surface charges and ion exchange. Whereas biochar component provides a larger specific surface area (467.8 m2/g). Batch adsorption experiments of biochar @ layered double hydroxide (BC@LDH) showed enhanced adsorption performance (832.9 mg/g), compared to pristine LDH (420.3 mg/g) and unmodified biochar (548.5 mg/g). Adsorption data were best interpreted (R2 = 0.99) by pseudo second order, Freundlich, and Temkin isotherm models. Adsorption was a synergism of LDH and biochar physiochemical properties, whereas pore-filling was the primary mechanism. The recyclability of BC@LDH confirmed its good structural stability. This study introduces a sustainable and efficient method for synthesizing a versatile adsorbent with superior antibiotic removal.

Selective adsorption of nitrate in water by organosilicon quaternary ammonium salt modified derived nickel-iron layered double hydroxide: Adsorption characteristics and mechanism

Nitrate (NO3-) is a widespread pollutant in the water environment. Due to its physicochemical properties, such as negative monovalent charge, traditional adsorption treatment processes have low selectivity for NO3- removal, resulting in low removal efficiency of NO3- by adsorbents in the presence of interfering ions. Therefore, to improve the adsorption selectivity and efficiency of NO3-. In this study, we used organosilicon quaternary modified derived nickel-iron layered double hydroxide (NiFe-MLDH/OQAS) for selective removal of NO3-. NiFe-MLDH/OQAS has a flowery globular structure, with interconnected nanosheets on the surface providing more adsorption sites for NO3-, which improves the adsorption rate and adsorption amount. What's more, the nitrate removal rate of NiFe-MLDH/OQAS only decreased by about 14.36% in the presence of the same concentration of interfering ions, and the maximum adsorption amount reached 61.05 mg/g, showing good selectivity and adsorption amount. Various characterization analyses indicate that the nitrate selectivity of NiFe-MLDH/OQAS is attributed to its unique layer spacing, as well as the abundant functional groups on the material surface. Finally, we demonstrated through experiments that NiFe-MLDH/OQAS has good cyclic regeneration ability and environmental safety. These findings demonstrate the great potential of NiFe-MLDH/OQAS for selective adsorption of NO3-.

Preparation of ZIF-67/C3N4 composite material and adsorption of tetracycline hydrochloride

In recent years, wastewater treatment to remove tetracycline hydrochloride (TCH) has received much attention in water treatment problems. ZIF-67/C3N4 composite adsorbent, a nanosheet structured material stacked with MOFs, was prepared by in situ growth method, which has high adsorption activity for tetracycline hydrochloride in wastewater. Comparing the effect of monomeric and composite adsorbents, Z6C2 had the best adsorption effect (206 mg·g-1), which was 77.6% higher than that of ZIF-67 (116 mg·g-1) and 10.8 times higher than that of C3N4 (19 mg·g-1). The structure of ZIF-67 stacked on C3N4 nanosheets has an excellent specific surface area and number of active sites, as well as π-π interactions, electrostatic interactions, and hydrogen bonding interactions between the adsorbent and TCH, which combine to enhance the adsorption performance. The adsorption process is accompanied by a combination of chemisorption, mass transport, and internal diffusion rate-limiting. It was shown that the adsorption process is favorable for monolayer adsorption as well as a heat absorption reaction that proceeds spontaneously. The adsorbent exhibits good stability and adsorption capacity, which may be suitable for efficient and low-cost water purification.

In situ synthesis of multivariant zeolitic tetrazolate imidazole frameworks (ZTIFs) with uncoordinated N-heteroatom sites for efficient adsorption of antiviral drugs

The current outbreak of the coronavirus (COVID-19) pandemic has significantly increased the global usage of antiviral drugs (AVDs), leading to higher concentrations of antibiotics in water pollution. To address this current issue, a new kind of adsorbent named isostructural zeolitic tetrazolate imidazolate frameworks (ZTIFs) were synthesized by combining imidazole and tetrazolates into one self-assembly approach by adjusting pores and stability of frameworks. The incorporation of imidazole ligand progressively increased the stability of frameworks. Furthermore, increasing the content of tetrazolate ligand greatly improved the adsorption performance due to N-rich sites by increasing the pore size. The obtained adsorbent composite exhibits macroporous structure up to 53.05 nm with excellent structural stability. Owing to their macropores and highly exposed active sites, the synthesized ZTIFs exhibit the maximum adsorption capacity for oseltamivir (OT) and ritonavir (RT) of 585.2 mg/g and 435.8 mg/g, respectively. Moreover, the adsorption uptake and saturation process were rapid compared to simple MOF. Within 20 min, both pollutants achieved equilibrium. The adsorption isotherms were best interpreted by Pseudo second order kinetics. The adsorption of AVDs on ZTIFs was spontaneous, exothermic, and thermodynamically feasible. The DFT calculations and characterization results after adsorption demonstrate that π-π interaction, pore filling, surface complexation, and electrostatic interaction were the primary features of the adsorption mechanism. The prepared ZTIFs composite exhibits high chemical, mechanical and thermal stability and can be recycled multiple times without destroying its morphology and structure. The adsorbent regeneration for several cycles impacted the operational cost and the eco-friendly characteristic of the process.

Adsorption of hexavalent chromium, Rhodamine B and Congo red simultaneously in aquatic by zeolitic imidazolate framework coupling carbon nanotubes

Zeolitic imidazolate framework/carbon nanotube (ZIF-67/CNTs) was prepared by precipitation method. ZIF-67/CNTs maintained the characteristics of large specific surface area and high porosity of ZIFs, showing stable cubic structure. The adsorption capacities of ZIF-67/CNTs for Cong red (CR), Rhodamine B (RhB) and Cr(VI) were 36.82 mg/g, 1421.29 mg/g and 716.67 mg/g under the conditions of 2:1, 3:1 and 1:3 masses of ZIF-67 and CNTs, respectively. The optimum adsorption temperature of CR, RhB and Cr(VI) were 30 °C, and the removal rates at the adsorption equilibrium were 81.22%, 72.87% and 48.35%. The adsorption kinetic model of the three adsorbents on ZIF-67/CNTs was consistent with the quasi-second order reaction model, and the adsorption isotherms were more consistent with adsorption law of Langmuir. The adsorption mechanism for Cr(VI) was mainly electrostatic interaction, and the adsorption mechanism for azo dyes was the combination of physical and chemical adsorption. This study would provide theoretical basis for further developing metal organic framework (MOF) materials for environmental applications.

Green synthesize of nano-MOF-ethylcellulose composite fibers for efficient adsorption of Congo red from water

Two novel MOF- ethyl cellulose (EC)- based nanocomposites have been designed and synthesized in water by electrospinning and applied for adsorption of congo red (CR) in water. Nano- Zeolitic Imidazolate Framework-67 (ZIF-67), and Materials of Institute Lavoisier (MIL-88A) were synthesized in aqueous solutions by a green method. To enhance the dye adsorption capacity and stability of MOFs, they have been incorporated into EC nanofiber to prepare composite adsorbents. The performance of both composites in the absorption of CR, a common pollutant in some industrial wastewaters, has then been investigated. Various parameters including initial dye concentration, the dosage of the adsorbent, pH, temperature and contact time were optimized. The results indicated 99.8 and 90.9% adsorption of CR by EC/ZIF-67 and EC/MIL-88A, respectively at pH = 7 and temperature at 25 °C after 50 min. Furthermore, the synthesized composites were separated conveniently and successfully reused five times without significant loss of their adsorption activity. For both composites, the adsorption behavior can be explained by pseudo-second-order kinetics, Intraparticular diffiusion and Elovich models demonstrated that the experimental data well matched to the pseudo-second-order kinetics. Intraparticular diffiusion model showed that the adsorption of CR on EC/ZIF-67 and EC/MIL-88a took place in one and two steps, respectively. Freundlich isotherm models and thermodynamic analysis indicated exothermic and spontaneous adsorption.

Carboxymethylcellulose/Hydrotalcite Bionanocomposites as Paraben Sorbents

In this work, we synthesized several bionanocomposites of hydrotalcites containing carboxymethylcellulose as interlayer anion (HT-CMC) to be used as sorbents for parabens, a family of emergent pollutants (specifically, for 4-methyl-, 4-propyl- and 4-benzylparaben). Bionanocomposites were obtained by ultrasound-assisted coprecipitation and characterized by X-ray diffraction analysis, fourier transform infrared and raman spectroscopies, elemental and thermogravimetric analysis, scanning and transmission electron microscopies and X-ray fluorescence. All materials proved to be efficient sorbents for parabens through a process conforming to a pseudo second-order kinetics. The experimental adsorption data fitted the Freundlich model very closely and were also highly correlated with the Temkin model. The effects of pH, adsorbate concentration, amount of sorbent and temperature on the adsorption process was evaluated, obtaining the best results for methylparaben adsorption at pH 7, 25 mg of adsorbent and 348 K. The sorbent, HT-CMC-3, showed the highest adsorption capacity (>70%) for methylparaben. Furthermore, a reusability study showed that the bionanocomposite is reusable after its regeneration with methanol. The sorbent still retained its adsorption capacity for up to 5 times with a little loss of efficiency (<5%).

Rational construction and understanding the effect of metal cation substitution of three novel ternary Zn-Co-Ni-LDHs from 2D to 3D and its enhanced adsorption properties for MO

The layered double hydroxides (LDHs) have attracted attention in the water treatment field. In this paper, three novel ternary Zn-Co-Ni-LDH adsorbents were prepared successfully through rational construction from 2D to 3D using triethanolamine (TEA) as an alkali source and a structural controlling reagent by hydrothermal technique. Samples were characterized by the SEM, XRD, XPS, FTIR, BET, solid-state UV/vis spectra, and TG. Three Zn-Co-Ni-LDHs exhibited higher crystallinity and surface area which were beneficial to the adsorption for methyl orange (MO). The maximum adsorption capacity of three Zn-Co-Ni-LDH adsorbents can even reach as high as 1871.65 mg·g^-1, 1799.56 mg·g^-1, and 1646.44 mg·g^-1 for MO, respectively, which surpass those of most previously reported LDH-based adsorbents. The pseudo-second-order kinetic equation fitted the kinetic data of adsorption, while the equilibrium adsorption isotherm data followed the Langmuir model. The adsorption mechanism, electrochemical, and the antibacterial properties of three Zn-Co-Ni-LDHs were also discussed. This results not only demonstrates that three Zn-Co-Ni-LDHs are practical interest as an efficient adsorbent for the removal of MO from dye waste water, but also provides a strategy for the rational design through three ternary Zn-Co-Ni-LDHs from 2D to 3D.

A Fe3O4 nanospheres/carbon core–shell structure for effective removal of pollutants from water

The treatment of wastewater by adsorption is a good alternative technique and attracts extensive attention worldwide due to its versatility, scalability, and low operational costs. In this work, a Fe3O4 nanospheres/carbon core–shell structure is fabricated by combination of a template method and calcination. The morphology and crystal structure of the synthesized composite are characterized by transmission electron microscopy, X-ray powder diffraction, Fourier transform infrared spectrometer, and from nitrogen adsorption–desorption isotherms, confirming that the carbon layer with a porous structure is successfully loaded onto the surface of the face-centered cubic Fe3O4 nanospheres to form a core–shell structure. The adsorption performance of the Fe3O4 nanospheres/carbon core–shell structure is investigated by studying the effects of the initial pH value of the solution, the contact time, the initial concentration of the pollutants, the adsorption temperature, and the amount of adsorbent. The Fe3O4 nanospheres/carbon core–shell structure effectively removes heavy metal Chromium(VI) and a reactive light yellow dye. The results of batch experiments show that the removal efficiencies of heavy metal Chromium(VI) and the reactive light yellow dye are close to 100% under optimized conditions. The good adsorption performance of the Fe3O4 nanospheres/carbon core–shell structure toward various types of pollutants suggests a potential application in wastewater treatment.

Effect of nickel (II) on the performance of anodic electroactive biofilms in bioelectrochemical systems

The impact of nickel (Ni²⁺) on the performance of anodic electroactive biofilms (EABs) in the bioelectrochemical system (BES) was investigated in this study. Although it has been reported that Ni²⁺ influences microorganisms in a number of ways, it is unknown how its presence in the anode of a BES affects extracellular electron transfer (EET) of EABs, microbial viability, and the bacterial community. Results revealed that the addition of Ni²⁺ decreased power output from 673.24 ± 12.40 mW/m² at 0 mg/L to 179.26 ± 9.05 mW/m² at 80 mg/L. The metal and chemical oxygen demand removal efficiencies of the microbial fuel cells (MFCs) declined as Ni²⁺ concentration increased, which could be attributed to decreased microbial viability as revealed by SEM and CLSM. FTIR analysis revealed the involvement of various microbial biofilm functional groups, including hydroxyl, amides, methyl, amine, and carboxyl, in the uptake of Ni²⁺. The presence of Ni²⁺ on the anodic biofilms was confirmed by SEM-EDS and XPS analyses. CV demonstrated that the electron transfer performance of the anodic biofilms was negatively correlated with the various Ni²⁺ concentrations. EIS showed that the internal resistance of the MFCs increased with increasing Ni²⁺ concentration, resulting in a decrease in power output. High-throughput sequencing results revealed a decrease in Geobacter and an increase in Desulfovibrio in response to Ni²⁺ concentrations of 10, 20, 40, and 80 mg/L. Furthermore, the various Ni²⁺ concentrations decreased the expression of EET-related genes. The Ni²⁺-fed MFCs had a higher abundance of the nikR gene than the control group, which was important for Ni²⁺ resistance. This work advances our understanding of Ni²⁺ inhibition on EABs, as well as the concurrent removal of organic matter and Ni²⁺ from wastewater.

Adsorption of Methyl Orange from an Aqueous Solution onto a BPPO-Based Anion Exchange Membrane

In this research, the development of a novel brominated poly(2,6-dimethyl-1,4-phenylene oxide) (BPPO)-based homogeneous anion exchange membrane (AEM) via the solution casting method was reported. Fourier transform infrared spectroscopy was used to confirm the successful development of the BPPO-based AEM. The prepared AEM showed excellent thermal stability. It exhibited an ion exchange capacity of 2.66 mg/g, a water uptake (W _R) of 68%, and a linear swelling ratio of 31%. Methyl orange (MO), an anionic dye, was used as a model pollutant to evaluate the ion exchange ability of the membrane. The adsorption capacity of MO increased with the increase in contact time, membrane dosage (adsorbent), temperature, and pH while declined with the increase in initial concentration of MO in an aqueous solution and molarity of NaCl. Adsorption isotherm study showed that adsorption of MO was fitted well to the Freundlich adsorption isotherm because the value of the correlation coefficient (R ² = 0.974) was close to unity. Adsorption kinetics study showed that adsorption of MO fitted well to the pseudo-second-order kinetic model. Adsorption thermodynamics evaluation represented that adsorption of MO was an endothermic (ΔH° = 18.72 kJ/mol) and spontaneous process. The AEM presented a maximum adsorption capacity of 18 mg/g. Moreover, the regeneration of the prepared membrane confirmed its ability to be utilized for three consecutive cycles. The developed BPPO-based AEM was an outstanding candidate for adsorption of MO from an aqueous solution.

Cadmium ion removal from aqueous media using banana peel biochar/Fe3O4/ZIF-67

In the present study, banana peel waste was used as a suitable source for biochar production. The banana peel biochar (BPB) was modified using Fe₃O₄ magnetic and ZIF-67 nanoparticles. The modification of the BPB surface (4.70 m²/g) with Fe₃O₄ and Fe₃O₄/ZIF-67 significantly increased the specific surface of the nanocomposites (BPB/Fe₃O₄: 78.83 m²/g, and BPB/Fe₃O₄/ZIF-67: 1212.40 m²/g). The effect of pH, temperature, contact time, adsorbent dose, and concentration of Cd²⁺ on the efficiency of the Cd²⁺ adsorption was explored. Maximum adsorption efficiencies for BPB (97.76%), BPB/Fe₃O₄ (97.52%), and BPB/Fe₃O₄/ZIF-67 (99.14%) were obtained at pH 6, Cd²⁺ concentration of 10 mg/L, times of 80 min, 50 min, and 40 min, and adsorbent doses of 2 g/L, 1.5 g/L, and 1 g/L, respectively. Thermodynamic measurements indicated that the process is spontaneous and exothermic. The maximum capacity of Cd²⁺ adsorption using BPB, BPB/Fe₃O₄, and BPB/Fe₃O₄/ZIF-67 were obtained 20.63 mg/g, 30.33 mg/g, and 50.78 mg/g, respectively. The Cd²⁺ adsorption using magnetic nanocomposites followed the pseudo-first-order kinetic model. The results showed that studied adsorbents especially BPB/Fe₃O₄/ZIF-67 have a good ability to adsorb-desorb Cd²⁺ and clean an effluent containing pollutants.

Metal-organic framework-mediated synthesis of hierarchical layered double hydroxide for high-efficiency enrichment of phosphopeptides

When applied as adsorbents for phosphopeptides enrichment, two-dimensional (2D) layered double hydroxides (LDHs) are usually limited by the disadvantages of buried affinity sites and reduced specific surface area. Multifarious exfoliation strategies have been implemented to compensate for these deficiencies, but tedious exfoliation process cannot meet the requirements of LDHs as high-efficiency adsorbents. Incorporating LDHs with three-dimensional (3D) template can avoid tedious exfoliation and produce hierarchical LDHs with large specific surface area and massive affinity sites. Herein, a hierarchical LDH (denoted as Fe₃O₄@ZIF-8@Zn-Ga LDH) was prepared by metal-organic framework (MOF)-mediated synthesis strategy, and a magnetic solid-phase extraction (MSPE) platform was constructed and employed for phosphopeptides enrichment with high efficiency. The unique 3D structure and abundant metal nodes of MOF provide 3D template and metal sources for in-situ nucleation and generation of LDH. Large specific surface area and massive exposed Zn and Ga endow Fe₃O₄@ZIF-8@Zn-Ga LDH with high enrichment efficiency toward phosphopeptides from complicated biological samples. With the aid of mass spectrometry (MS) techniques, we profiled endogenous or global phosphopeptides from human saliva and serum, which proved the practical application value of this material.

Preparation of aminated porous polyacrylonitrile nanofibers as adsorbent for methyl orange removal

In this study, porous electrospinning polyacrylonitrile nanofiber (PPAN) surface functionalization with amine groups is studied for methyl orange (MO) dye removal from aqueous solution. A series of adsorption experiments were carried out to investigate the influence of initial solution pH value, contact time, initial solution concentration, and adsorption temperature on the adsorption performance. The experimental results showed that the removal of MO on these PPAN-PEI and PPAN-TEPA nanofibrous mats was a pH-dependent process with the maximum adsorption capacity at the initial solution pH of 3, and that the PPAN-PEI and PPAN-TEPA nanofibrous mats could be regenerated successfully after 4 recycling processes. The adsorption equilibrium data were all fitted well to the Langmuir isotherm equation, with maximum adsorption capacity of 1414.52 mg g⁻¹ and 1221.09 mg g⁻¹ for PPAN-PEI and PPAN-TEPA, respectively. The kinetic study indicated that the adsorption of MO could be well fitted by the pseudo-second-order equation and Weber–Morris model. Thermodynamic parameters such as free energy, enthalpy, and entropy of adsorption of the MO were also evaluated, and the results showed that the adsorption was a spontaneous exothermic adsorption process.

Amino functionalized porous polyacrylonitrile electrospun nanofibers were fabricated, which have good adsorption performance for MO in an acidic environment.

Surface engineering of silica based materials with Ni-Fe layered double hydroxide for the efficient removal of methyl orange: Isotherms, kinetics, mechanism and high selectivity studies

Herein, low-cost diatomite (DE) and bentonite (BE) materials were surface modified with Ni-Fe layered double hydroxide (LDHs) (represented as NFD and NFB respectively), using a simple co-precipitation procedure for the removal of methyl orange (MO) dye from water. The adsorbents of both before and after MO adsorption have been studied by XRD, N₂ adsorption-desorption isotherm, FTIR, FESEM-EDX and XPS characterization. The zeta potential analysis was used to observe the surface charge of adsorbents within the pH ranges of 4-10. The MO removal efficiency was significantly improved after LDHs modification, showing a 94.7% and 92.6% efficiency for NFD and NFB at pH 6, respectively. Whereas bare DE and BE have shown removal efficiency of 15.5% and 4.9% respectively. The maximum adsorption capacities of NFD and NFB using the Langmuir isotherm model were found to be 246.9 mgg^-1 and 215.9 mgg^-1 respectively. The designed NFD showed high selectivity towards anionic-based dyes from water and also the effect of salts shows the dye removal percentage was increased and decreased for the addition of Na₂SO₄ and NaCl, respectively. The reusability of NFD and NFB have been studied for a maximum of five cycles and they can remove MO up to four cycles. Therefore, the designed adsorbents can be very effective towards the removal of MO from water and they may be useful for dye-based wastewater treatment.

Synthesis of highly porous three-dimensional PVA/GO/ZIF-67 cryogel for the simultaneous treatment of waters contaminated with cadmium (II) and lead (II) heavy metal ions

In this research, PVA/GO/ZIF-67 cryogel as a highly porous three-dimensional polymeric adsorbent was synthesized by freeze-drying method and applied for the simultaneous removal of Cd2+ and Pb2+ ions from contaminated...

Recent progress in the synthesis of Layered Double Hydroxides and their application for the adsorptive removal of dyes: A review

Layered double hydroxides (LDHs), also known as anionic clays, are lamellar inorganic solids with a brucite-like structure and consist of positively charged metal hydroxide sheets intercalated by anions and water molecules. Choice of LDH is beneficial as it displays properties like simple synthesis procedures, adjustable structure, stability, large surface area, homogeneous positive charge distribution over the surface, interplanar spacing, and versatility to synthesize a variety of composites. Due to these properties LDHs act as efficient adsorbents for wastewater treatment. This review presents a detailed overview of the removal of hazardous organic dyes using different LDHs and LDH-hybrids/composites. The review also incorporates methods of synthesis of various LDHs and composites and the effect of their morphology on dye removal capacity. The effects of adsorption variables such as pH, adsorbent dosage, initial concentration of dye, contact time on the adsorption of these materials are also explained along with adsorption isotherms, kinetics and operative mechanisms. This article incorporates 156 references, majority of which have been taken from the available literature of last 5 years.

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.

Enhanced adsorption properties of organic ZnCr-LDH synthesized by soft template method for anionic dyes

Organic ZnCr-LDH (ST-LDH) was synthesized by a facile one-step hydrothermal technique using methyl orange (MO) as a soft template agent, which can efficiently remove methyl orange (MO), Congo red (CR), and orange II (OII) from aqueous solution. The microstructure of ST-LDH by modifying changed obviously, from the cellular structure to the stacking structure formed by the face-face contact of hydrotalcite nanosheets, which resulted in much more exchangeable nitrate ions to remain in the interlayer space. The pre-insertion of benzene sulfonate as a pillar expanded the interlayer gallery, which facilitated the pollutant anions (MO, CR, and OII) into the interlayer of LDH in the subsequent adsorption process. The maximum adsorption capacity of ST-LDH for MO, CR, and OII was 4200.8 mg/g, 1252.0 mg/g, and 1670.6 mg/g, respectively, which is approximately 1.86 times, 1.8 times, and 2.32 times that of the pristine NO₃-LDH, respectively. The removal mechanism of anionic dyes was determined as anion exchange between NO₃^- anions and dye molecules. The adsorption behavior for MO and OII is multilayer adsorption, while the adsorption behavior for CR is monolayer adsorption. The adsorption process mainly was controlled by the chemical bonding between the dye molecules and adsorbent active sites. The LDH can be effectively regenerated by photocatalysis after MO adsorption. The ST-LDH has a great potential to be used as a high-efficient adsorbent to remove anionic dyes from aqueous solution. The schematic illustration of the synthetic process of soft template agent modified and unmodified hydrotalcites by one-pot hydrothermal method and the adsorption process of MO by ST-LDH were shown in Fig. 12. Modified hydrotalcite (ST-LDH) was prepared using methyl orange (MO) as a soft template agent. Compared with unmodified hydrotalcite (NO₃-LDH), the insertion of benzene sulfonate anions into the hydrotalcite layer resulted in the increase of the interlayer spacing from 8.269 to 8.654Å. The LDH host structure pre-intercalated by benzene sulfonate anions evolved into pillared materials in interlayer; benzene sulfonate anions as a column expanded the interlayer spacing of (003) base plane, which facilitated the pollutant anions (MO, CR, and OII) into the interlayer of ST-LDH and exchanged with NO₃^- anion in the subsequent adsorption process. It can be inferred that in the process of modification hydrotalcite by benzene sulfonate, a small amount of benzene sulfonate anions pre-inserted into the gallery of hydrotalcite with a monolayer model in the process of hydrotalcite modification, and its inclination angle is calculated to be about 29.1°. After ST-LDH sample adsorbed the MO molecules, dye molecules intercalated into the LDH host, and successful exchange with NO₃^- anions, the d₀₀₃ value increased to 24.78 Å. A large amount of MO^- anions were intercalated into the gallery of ST-LDH with a bilayer model according to the Freundlich isotherm model, and the tilting angle increases to 53.6°. The adsorption capacity of MO by ST-LDH was significantly enhanced to 4200.8 mg/g, which was much higher than that of NO₃-LDH (2252.8 mg/g). Schematic illustration of the synthetic process of LDH materials and adsorption process of MO by ST-LDH.

In situ growth zeolite imidazole framework materials on chitosan for greatly enhanced antibacterial effect

Zeolite imidazole framework materials (ZIFs) are a new type of antibacterial material with high chemical and thermal stability, and good antibacterial effect. However, powder ZIFs materials have the disadvantages of difficult separation and easy aggregation, which limit their application. In this work, ZIFs and chitosan (CS) were compounded by in-situ growth method to prepare a new antibacterial agent. The synergism of CS and ZIFs can effectively promote antibacterial effect compared with CS and pristine ZIFs, and CS/ZIF-67(1:6) has the best antibacterial activity, and its inhibitory rate (in 15 h) of E. coli is 96.75%, and the inhibitory rate of S. aureus reaches as high as 100%. This composites can effectively cause bacterial cell membrane rupture and leakage of internal nucleic acid and protein, leads to achieve antibacterial effect, and also exhibit excellent long-term (at least 5 days) antibacterial properties, the leaching of cobalt is below than 0.5 mg·L^-1, and this composites are with excellent bio-compatibility.