Facile synthesis of magnetic zinc metal‐organic framework for extraction of nitrogen‐containing heterocyclic fungicides from lettuce vegetable samples

We present a simple method for the fabrication of a magnetic amino‐functionalized zinc metal‐organic framework based on a magnetic graphene oxide composite. The resultant framework exhibited a porous 3D structure, high surface area and good adsorption properties for nitrogen‐containing heterocyclic fungicides. The adsorption process and capacity indicated that the primary adsorption mechanism might be hydrogen bonding and π‐π conjugation. In addition, an optimized protocol for magnetic solid phase extraction was developed (such as adsorbent content, pH, and desorption solvent), and utilized for the extraction of nitrogen‐containing heterocyclic fungicides from vegetable samples. Quantitation by high performance liquid chromatography coupled with tandem mass spectrometry offered a detection limit of 0.21–1.0 μg/L (S/N = 3) with correlation coefficients larger than 0.9975. These results demonstrate that magnetic amino‐functionalized zinc metal‐organic framewor is a promising adsorbent for the extraction and quantitation of nitrogen‐containing heterocyclic fungicides.     

Effective adsorption of Hg(II) ions by new ethylene imine polymer/β-cyclodextrin crosslinked functionalized magnetic composite

A new effective magnetic composite material was prepared successfully for adsorption Hg(II) ions by introducing β-cyclodextrin/ethylene imine polymer to the mesoporous silica. The morphology and structure of EIP-β-CD magnetic adsorbents were characterized by FT-IR, XR, DTG, XPS and SEM technologies. The effect of many factors were discussed detailedly such as adsorption time, initial concentration, pH, different composition of adsorbent and adsorption temperature. It was found that EIP-β-CD showed excellent adsorption capacity, high selectivity, good reutilization and fast adsorption rate. The maximum adsorption capacity was 248.72 mg/g and the best removal rate was 99.49 % under the optimized experimental conditions. The kinetic and thermodynamic study showed typical characteristic of chemical adsorption, exothermic and spontaneous. The best mass proportion of β-cyclodextrin, ethylene imine polymer and glutaraldehyde was 1.0:0.4:0.2, and proper β-cyclodextrin can develop the adsorption capacity for Hg(II) ions in this adsorbent. The possible adsorption mechanism was investigated in detail. After the fifth cycle experiment, this new adsorbent still showed excellent adsorption capacity which indicated that it has great potential for Hg(II) ions cleanup in water solution.     

Porous multicomponent chitosan/poly(ε-caprolactone)-block poly (ethylene glycol)/SiO2 aerogel@polydopamine membrane for Congo red adsorption

A composite adsorbent, chitosan//poly (ε-caprolactone)-block poly (ethylene glycol)/SiO₂ aerogel@polydopamine (CS/PCL-b-PEG/SA@PDA) membrane was prepared for the adsorption of organic dyes. The matrix polymer materials of this novel adsorbent were eco-friendly. SiO₂ aerogel with nanoporous network construction was fixed in the multicomponent polymer fibers through simultaneous electrospinning-electrospray technology followed by modification of polydopamine (PDA). The composite adsorbent had a maximum adsorption capacity of 598.8 mg/g for Congo red (CR) and possessed good reusability performance. This adsorbent showed excellent performance for the selective adsorption of relatively large molecule CR dyes even under high concentration of small molecule methyl orange (MO) dyes or 1 M of salt solution. The adsorption mechanism indicated that the –NH₂ and –OH groups in adsorbent could generate the stronger electrostatic attraction with the –SO₃^- groups in CR. Meanwhile, the sufficient adsorption spaces of the adsorbent were constructed by the porous network structure of SiO₂ aerogel, the accumulation of PDA particles and the porous structure of the multicomponent composite membrane. The work provided a proactive study in designing an adsorbent for the selective adsorption of organic dyes.     

Preparation of magnetic composite adsorbents from laterite nickel ore for organic amine removal

Magnetic composite adsorbent (MCA) was prepared successfully using laterite nickel ore. The effectiveness of MCA as an adsorbent was evaluated for removal trimethylamine from aqueous environment. In this technological route, the utilization of solid wastes, wastewater treatment and adsorbent recovery were considered comprehensively. The MCA was characterized by techniques, including XRD, SEM, TEM, EDS, VSM and adsorption-desorption of nitrogen at 77 K. The adsorption processes were best described by pseudo-second-order kinetic model and controlled by intraparticle and surface diffusion processes. Langmuir and Freundlich isotherm models were used to match the adsorption equilibrium data. Freundlich isotherm was the best fitting curve for the sorption equilibrium data. The adsorption mechanism was further interpreted by Gibbs free energy, entropy and enthalpy calculated by thermodynamic equation. The negative values of Gibbs free energy changes (ΔG) manifest that the adsorbing process is spontaneous. The results show that laterite nickel ore can be made into MCA for organic amine removal from polluted water.     

Preparation and characterization of magnetic bioadsorbent for adsorption of Cd(II) ions

A facile magnetic chitosan composite used for heavy metal ions removal was prepared. The adsorbents with large specific area and rich carboxyl groups exhibited good removal of Cd(II) ions and could be easily separated with magnetic separation. The adsorption capacity of Cd(II) was 48 ​mg ​g⁻¹ and the removal efficiency reached 86.7% after five cycles. Thus, the prepared magnetic chitosan composite could act as a potential adsorbent for Cd(II) ions removal.     

Optimization of cadmium adsorption from aqueous solutions by functionalized graphene and the reversible magnetic recovery of the adsorbent using response surface methodology

Novel functionalized graphene adsorbent was prepared and characterized using different techniques. The prepared adsorbent was applied for the removal of cadmium ions from aqueous solution. A response surface methodology was used to evaluate the simple and combined effects of the various parameters, including adsorbent dosage, pH, and initial concentration. Under the optimal conditions, the cadmium removal performance of 70% was achieved. A good agreement between experimental and predicted data in this study was observed. The experimental results revealed of cadmium adsorption with high linearity follow Langmuir isotherm model with maximum adsorption capacity of 502 mg g^?1, and the adsorption data fitted well into pseudo‐second order model. Thermodynamic studies showed that adsorption process has exothermic and spontaneous nature. The recommended optimum conditions are: cadmium concentration of 970 mg L^?1, adsorbent dosage of 1 g L^?1, pH of 6.18, and T = 25 °C. The magnetic recovery of the adsorbent was performed using a magnetic surfactant to form a noncovalent magnetic functionalized graphene. After magnetic recovery of the adsorbent both components (adsorbent and magnetic surfactant) were recycled by tuning the surface charges through changing the pH of the solution. Desorption behavior studied using HNO₃ solution indicated that the adsorbent had the potential for reusability.     

Synthesis of PS/RB-Cs and its use in the treatment of water polluted with heavy metals

Polystyrene waste are non-biodegradable materials that causes harm to the environment. Red brick waste resulting from demolition and reconstruction are an obstacle to its disposal. To solve this problem and meet modern sustainability standards, this study utilized polystyrene (PS) foam and red brick construction waste to prepare composite materials (PS/RB-Cs) as a new efficient adsorbent. The PS/RB-Cs composite as an adsorbent was characterized using a UV–Vis Spectrophotometer, Energy Dispersive X-ray Spectroscopy (EDX), Scanning Electron Microscope (SEM), and transmission electron microscopy (TEM), which showed a clear spectrum shift after using PS/RB-Cs as an adsorbent. The PS/RB-Cs was characterized by a porous structure with higher surface area and high stability. The efficiency of the PS/RB-Cs in treating water contaminated with heavy metals such as cobalt and nickel was verified under different initial concentrations, temperatures, doses, pH, and contact times. The experimental q_e values were consistent with the q_e calculated values and were approximately 8 mg/g. The adsorption isotherm models showed that the adsorption results fit the Langmuir, Freundlich and Flory-Huggins isotherm models and that the process was favorable. By applying pseudo-first-order (PFO) and pseudo-second-order (PSO) kinetic models, the adsorption process was found to follow PSO. The findings of this research validated that the composite material that was prepared serves as a potent adsorbent for the treatment of water that has been polluted by heavy metals.     

Polyethyleneimine-grafted polyphosphazene microspheres for rapid and efficient capture of anionic dyes from wastewater

Developing novel adsorbent to capture organic contaminants from wastewater rapidly and efficiently is highly desirable for waste treatment and environmental restoration. Herein, we reported a new amino-rich spherical adsorbent (PZS-PEI) for highly-efficient uptake of anionic dyes from aqueous solution. The PZS-PEI adsorbent was fabricated through a two-step process including synthesis of PZS-Cl microspheres via room temperature polymerization of hexachlorocyclotriphosphazene with bis(4-hydroxyphenyl) sulfone and subsequent surface grafting reaction of PZS-Cl microspheres using branched polyethyleneimine (PEI). The microstructure of as-obtained PZS-PEI microspheres was fully characterized by scanning electron microscopy, Fourier transform infrared, X-ray photoelectron spectroscopy, zeta potential, and N₂ adsorption test. The adsorption performance of the PZS-PEI microspheres towards organic dyes was evaluated through carrying out a series of studies including various influence factor analysis, adsorption isotherm, kinetics, and thermodynamics. Results show that the PZS-PEI adsorbent owned good adsorption selectivity towards anionic dyes, and the maximum adsorption capacities for methyl orange (MO), acid chrome blue K, eosin-Y reached 190.29, 152.90, and 92.34 mg/g at 25 °C, respectively. In addition, the uptake behavior of organic dye by the PZS-PEI adsorbent conformed to Freundlich isotherm and pseudo-second order kinetic model, and the adsorption process followed a three-stage intraparticle diffusion mode with an endothermic and spontaneous characteristic. Electrostatic interaction and hydrogen bonding were responsible for the highly-efficient adsorption of the PZS-PEI adsorbent towards typical anionic dye MO.     

Sol–gel polycondensation of tetraethoxysilane in ethanol in presence of vinyl modified guar gum: synthesis of novel nanocompositional adsorbent materials

Novel nanocomposite adsorbent materials were synthesized by condensation polymerization of TEOS in the presence of saponified guar-graft-poly(acrylonitrile) (SG) as template. The effect of changing the molecular size of SG on the final properties of the composite materials was investigated in this paper. The composites were thermally treated at temperatures ranging from 80 to 1100 °C, to obtain materials of different performance. The chemical, structural and textural characteristics of the composites were determined by FTIR, XRD, TGA-DSC and SEM studies. Their adsorption properties were monitored in terms of Zn (II) binding capacity which could be tailored by changing the template size and sintering temperature. The adsorption capacity of the composite at room temperature was enhanced five times when thermally treated at 900 °C with a maximum adsorption of 3.58 meq/g of the zinc (II). The adsorption could be further optimized to higher values and the materials could be successfully recycled for three consecutive cycles without any significant loss in the adsorption capacity.     

Preparation and characterization of nanocomposite,silica aerogel,activated carbon and its adsorption properties for Cd (II) ions from aqueous solution

A novel composite adsorbent, silica aerogel activated carbon was synthesized by sol-gel process at ambient pressure drying method. The composite was characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and Nitrogen adsorption/desorption isotherms (BET).In the present study, the mentioned adsorbent was used moderately for the removal of cadmium ions from aqueous solutions and was compared with two other adsorbents of cadmium, activated carbon and silica aerogel. The experiments of Cd adsorption by adsorbents were performed at different initial ion concentrations, pH of the solution, adsorption temperature, adsorbent dosage and contact time. Moreover, the optimum pH for the adsorption was found to be 6.0 with the corresponding adsorbent dosage level of 0.1 g at 60 °C temperature. Subsequently, the equilibrium was achieved for Cd with 120 min of contact time.Consequently, the results show that using this composite adsorbent could remove more than 60% of Cd under optimum experimental conditions. Langmuir and Freundlich isotherm model was applied to analyze the data, in which the adsorption equilibrium data were correlated well with the Freundlich isotherm model and the equilibrium adsorption capacity (q_e) was found to be 0.384 mg/g in the 3 mg/L solution of cadmium.     

Corncob-to-xylose residue (CCXR) derived porous biochar as an excellent adsorbent to remove organic dyes from wastewater

Biochar was prepared from corncob-to-xylose residue (CCXR) by KOH activation and anaerobic pyrolysis method. The effect of activation temperature on the microstructure of the biochar was studied. Results showed that the biochar prepared at 850°C (850NBC) possessed high specific surface area and exhibited excellent adsorption property. The maximum adsorption capacity of 2249 mg g⁻¹ was obtained when 850NBC was used for treating methylene blue (MB) solution. Adsorption isotherm fittings revealed that Langmuir and Freundlich models were applicable to 850NBC adsorption process, and the adsorption process was limited by adsorption site and the biochar surface functional groups. Furthermore, 850NBC showed good adsorption property when it was used to treat the other organic dyes of Congo red (751 mg g⁻¹), Orange II (735 mg g⁻¹), Indigo carmine (662 mg g⁻¹) and Methyl Orange (465 mg g⁻¹). Biochar 850NBC also possessed an acceptable recyclability which maintained 68.7% absorption capacity after 6 cycles when it was used to treat MB solution. These results proposed that 850NBC is expected to be a promising potential adsorbent for treating organic dyes waste water.     

Adsorption behavior of Pd(II) ions from aqueous solution onto pyromellitic acid modified-UiO-66-NH2

A new adsorbent was successfully fabricated by chemically linking pyromellitic acid onto a zirconium-based metal-organic framework composite for selective adsorption of Pd(II) from an aqueous solution. The adsorbent was characterized by Fourier transform infrared spectroscopy, Brunauer–Emmett–Teller equation and scanning electron microscope. The adsorption capacity, selectivity and repeatability of the adsorbent were tested by batch experiments. The optimum pH was 2.0, and the maximum adsorption capacity at room temperature was 226.1 mg/g. In the kinetic experiments, the adsorption process achieved equilibrium within 5 h and generally conformed to the quasi-second kinetics and Freundlich isotherm model. The N-H and OH groups on the adsorbent interacted with Pd(II) by electrostatic and coordination action. The adsorbent maintained excellent adsorption capacity after at least 5 cycles. At the same time, the selectivity of the adsorbent in aqueous solution is excellent from interfering ions. Therefore, the new adsorbent will have an obvious application prospect on the recovery of palladium.     

Activated carbon/MOFs composite: AC/NH2-MIL-101(Cr), synthesis and application in high performance adsorption of p-nitrophenol

P-nitrophenol (PNP), a hazardous phenolic material, should be eliminated from water in order to prevent damage to the marine ecosystem, animals as well as humans. Although adsorption seems to become the most widely used strategy, an effective and strong-capacity adsorbent to minimize PNP under the approved concentration is essential to discovering. In this study, a class of porous adsorbents composite was developed for the PNP removal from water. AC-NH₂-MIL-101(Cr) has chosen to boost the removal of PNP from water owing to extremely porous and stable in water. The fabricated composite has 2049 m².g⁻¹ large surface area and 0.93 cm³.g⁻¹ pore volume. The adsorption kinetics and isotherms were investigated. AC-NH₂-MIL-101(Cr) was found to exhibit an adsorption capacity of ~ 18.3 mg g⁻¹. The mechanism for this strong adsorption performance was suggested and related to affinity NO₂ groups of PNP and the unsaturated chromium site of AC-NH₂-MIL-101(Cr), the coulombic interaction via the hydrogen bond between the PNP and AC-NH₂-MIL-101(Cr) and π-π stacking interaction. AC-NH₂-MIL-101(Cr) composite also displayed exceptional stability and reusability after a successive PNP removal processes. This study provides new insight into developing and synthesizing extremely effective nanoporous material for organic contaminants disinfection from waste water based on MOFs.     

Kinetics and equilibrium studies of adsorption of chromium(VI) ion from industrial wastewater using Chrysophyllum albidum (Sapotaceae) seed shells

A new biosorbent has been prepared by coating Chrysophyllum albidum (Sapotaceae) seed shells with chitosan and/or oxidizing agents such as sulfuric acid. This study investigated the technical feasibility of activated and modified activated C. albidum seed shells carbons for the adsorption of chromium(VI) from aqueous solution. The sorption process with respect to its equilibria and kinetics as well as the effects of pH, contact time, adsorbent mass, adsorbate concentration and particle size on adsorption was also studied. The most effective pH range was found to be between 4.5 and 5 for the sorption of the metal ion. The pseudo-first-order rate equation by Lagergren and pseudo-second-order rate equation were tested on the kinetic data, the adsorption process followed pseudo-second-order rate kinetics, also, isotherm data was analyzed for possible agreement with the Langmuir and Freundlich adsorption isotherms, the Freundlich and Langmuir models for dynamics of metal ion uptake proposed in this work fitted the experimental data reasonably well. However, equilibrium sorption data were better represented by Langmuir model than Freundlich. The adsorption capacity calculated from Langmuir isotherm was 84.31, 76.23 and 59.63 mg Cr(VI)/g at initial pH of 3.0 at 30 °C for the particle size of 1.00–1.25 mm with the use of 12.5, 16.5 and 2.1 g/L of CACASC, CCASC and ACASC adsorbent mass, respectively. This readily available adsorbent is efficient in the uptake of Cr(VI) ion in aqueous solution, thus, it could be an excellent alternative for the removal of heavy metals and organic matter from water and wastewater.     

Facile synthesis of magnetic hybrid metal–organic frameworks with high adsorption capacity for methylene blue

A magnetic hybrid material (Fe₃O₄‐COOH/HKUST‐1) was easily synthesized via a two‐step simple solvothermal method. Through adding sodium acrylate directly into the synthesis of Fe₃O₄ spheres, the surface has more carboxyl groups. It is notable that the reactions proceed without use of organic surfactants. The magnetic hybrid material was characterized using various techniques. The magnetic hybrid material has a high specific surface area (430.15 m² g⁻¹) and excellent magnetism (23.65 emu g⁻¹). It is an efficient adsorbent for removing organic dyes like methylene blue (MB) from aqueous solution. It also can be easily recovered from liquid media using an external magnetic field. Adsorption experiment shows the magnetic hybrid material possesses a high adsorption capacity (118.6 mg g⁻¹), and has high adsorption efficiency (94.3%) after five adsorption cycles with ethanol (0.2% HCl) as eluent. The sorption kinetics and isotherm analysis indicate these sorption processes are better fitted to the pseudo‐second‐order and Langmuir equations. Thermodynamic study shows the sorption processes are spontaneous and endothermic.     

Effective removal of anionic dyes from aqueous solutions by novel polyethylenimine-ozone oxidized hydrochar (PEI-OzHC) adsorbent

The adsorption behavior of the anionic dyes Remazol Brilliant Blue R (RBBR) and Reactive Black 5 (RB5) from aqueous solutions by polyethylenimine ozone oxidized hydrochar (PEI-OzHC) was investigated. The adsorption capacities of both dyes increased with functionalization of PEI in the hydrochar adsorbent. The results of surface characterization (FTIR, BET, TGA, elemental analysis, and SEM) showed that PEI modification greatly enhanced the adsorbent surface chemistry with a slight improvement of adsorbent textural properties. In addition, the adsorption kinetics data showed an excellent adsorption efficiency as reflected in the high removal percentages of the anionic dyes. The Isotherm results indicated that RBBR and RB5 dye adsorption occurred via monolayer adsorption, and chemisorption was the rate-controlling step. The PEI-OzHC adsorbent possesses higher maximum Langmuir adsorption capacity towards RBBR (218.3 mg/g) than RB5 (182.7 mg/g). This increase in adsorption capacity is attributed to the higher number of functional groups in RBBR that interact with the adsorbent. This study reveals the potential use of adsorbents derived from pine wood hydrochar in municipal as well as industrial wastewater treatment. Furthermore, surface chemistry modification is proven as an effective strategy to enhance the performance of biomass-derived adsorbents.     

Adsorption properties and mechanism of sepiolite to graphene oxide in aqueous solution

Graphene oxide (GO) is widely used in various fields such as improving the performance of cement-based materials and making composite materials due to its large specific surface area and abundant oxygen-containing functional groups. However, it has also caused water pollution. To remove GO in aqueous solution, sepiolite (SEP) was used to adsorb it. The effects of pH, adsorbent quality, GO concentration, temperature and adsorption time on the ability of SEP to adsorb GO were investigated. The materials were characterized by SAP and laser particle size analyzer, and the adsorption performance and mechanism of SEP for GO were further analyzed by XRD, FTIR, SEM, TEM, XPS, AFM, and Zeta potential microscopic tests. The results showed that: 1) Under the conditions of temperature 303 K, pH = 3, adsorbent mass 30 mg, and initial concentration of GO 100 mg/L, the adsorption effect was the best, and the adsorption rate reached 94.8 %. 2) The adsorption reached equilibrium at 2160 min, and the adsorption process was more in line with the pseudo-second-order adsorption kinetic equation, and the adsorption behavior was controlled by chemical effects. 3) The adsorption of SEP to GO is more consistent with the Langmuir and Temkin adsorption isotherm model, and the reaction is a spontaneous, endothermic, and entropy-increasing process. Experiments showed that SEP had a strong adsorption capacity for GO, which provides a reference for the treatment of toxic GO in aqueous solution and the realization of water ecological protection.     

Synthesis of NiO coated chitosan-cenosphere buoyant composite for enhanced adsorptive removal of methylene blue

The objective of the present study is to utilize fly ash cenosphere to remove methylene blue (MB) from the water streams. Nickel oxide is a typical semiconductor used as proficient adsorbent material for degradation of dye with environment friendly applications due to its excellent chemical stability and high catalytic activity. The chitosan cenosphere buoyant composite coated with NiO was synthesized with hydrothermal grafting reaction using silane coupling agent and epichlorohydrin as a cross-linking reagent. The batch adsorption experiments were carried out with a cationic dye, methylene blue as a representative organic pollutant to investigate the adsorptive capabilities of the composite as adsorbent. The influence of pH (2-12), initial concentration of dye (50–200 mg/L), temperature (37–47 °C) and contact time (0–24 h) were taken as parameters in the study. On the relative elimination of MB, the effect of time and temperature were investigated. The adsorption kinetics for MB was correlated and found to observe the pseudo-second order kinetic model, whereas the equilibrium adsorption isotherm follows the Langmuir model (R² > 0.99). The results indicate that the floating fly ash cenosphere coated with NiO proved to be more responsive for enhanced degradation of methylene blue.     

Sorption of uranium(VI) from aqueous solution onto magnesium silicate hollow spheres

The sorption of uranium(VI) from aqueous solutions was investigated using synthesized magnesium silicate hollow spheres as a novel adsorbent. Batch experiments were conducted to study the effects of initial pH, amount of adsorbent, contact time and initial U(VI) concentrations on uranium sorption efficiency. The desorbing of U(VI) and the effect of coexisting ions were also investigated. Kinetic studies showed that the sorption followed a pseudo-second-order kinetic model. The Langmuir sorption isotherm model correlates well with the uranium sorption equilibrium data for the concentration range of 25–400 mg/L. The maximum uranium sorption capacity onto magnesium silicate hollow spheres was estimated to be about 107 mg/g under the experimental conditions. Desorption of uranium was achieved using inorganic acid as the desorbing agent. The practical utility of magnesium silicate hollow spheres for U(VI) uptake was investigated with high salt concentration of intercrystalline brine. This work suggests that magnesium silicate hollow spheres can be used as a highly efficient adsorbent for removal of uranium from aqueous solutions.     

Adsorption of La(III) onto GMZ bentonite: effect of contact time,bentonite content,pH value and ionic strength

Bentonite has been studied extensively because of its strong adsorption capacity. A local Na-bentonite named GMZ bentonite, collected from Gaomiaozi County (Inner Mongolia, China), was selected as the first choice of buffer/backfill material for the high-level radioactive waste repository in China. In this research, the adsorption of La (ΙΙΙ) onto GMZ bentonite was performed as a function of contact time, pH, solid content and metal ion concentrations by using the batch experiments. The results indicate that the adsorption of La (III) on GMZ bentonite achieves equilibration quickly and the kinetic adsorption follows the pseudo-second-order model; the adsorption of La (III) on the adsorbent is strongly dependent on pH and solid content, the adsorption process follows Langmuir isotherm. The equilibrium batch experiment data demonstrate that GMZ bentonite is effective adsorbent for the removal of La (III) from aqueous solution with the maximum adsorption capacity of 26.8 mg g⁻¹ under the given experimental conditions.