Graphene-supported biomimetic catalysts with synergistic effect of adsorption and degradation for efficient dye capture and removal

Design and development of iron porphyrin-based artificial enzymes system have been attracting a lot of attention.Herein,without any toxic reductant and harsh processing,we present a facile one-pot method to fabricate bifunctional catalytic nanocomposites consisting of graphene and hemin by using vitamin C as a mild reduction reagent.The presence of graphene helps the formation of a high degree of highly active and stable hemin on the graphene surface in a monomeric form through their π-π stackin...     

Synthesis and characterization of new polymers derived from 2-methyl-m-phenylenediamine as an effective adsorbent for cationic dye removal

The oxidative polymerizations of 2-methyl-m-phenylenediamine were performed to synthesize PMPDIA-A and PMPDIA-B polymers by H₂O₂ (35% aqueous solution) oxidant in acid-catalyzed ethanol and basic aqueous medium. Furthermore, PMPDIA-E polymer of 2-methyl-m-phenylenediamine was enzymatically synthesized by HRP (horseradish peroxidase) enzyme and H₂O₂ (35% aqueous solution) in dioxane/0.1 M phosphate tampon solution (pH = 7) mixture. The structures of 2-methyl-m-phenylenediamine and polymers were confirmed by FT-IR, NMR and UV–Vis spectrometer measurements. Molecular weight distributions, surface morphologies, thermal and fluorescence properties of polymers were determined from GPC, SEM, TG-DTA, DSC and fluorescence spectra analyses, respectively. CV and UV–Vis analyses were performed to determine the HOMO–LUMO energy levels, electrochemical (E_g′) and optical (E_g) band gaps values of MPDIA, PMPDIA-E, PMPDIA-A and PMPDIA-B. The electrochemical and optical band gaps values of polymers were lower than MPDIA, because of their polyconjugated structures. According to GPC measurements of polymers, the weight average molecular weights were between 5400 and 10400 Da. The fluorescence quantum yield of PMPDIA-E was calculated to be 9.15% in DMSO solution. The adsorption of methylene blue (MB) from aqueous solution on PMPDIA-B was studied. Adsorption isotherms and equilibrium adsorption capacities were determined by the fitting of the experimental data to two well-known isotherm models: Langmuir and Freundlich.     

Clay and charcoal composites: characterisation and application of factorial design analysis for dye adsorption

The characterisation of smectite clay, charcoal and prepared clay-charcoal composites was carried out through the X-ray diffractometry, energy dispersive X-ray spectroscopy (EDS), simultaneous thermal analysis (TGA/DTA), infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The analysis revealed the composites to have different characteristics from the precursor clay and charcoal, and a peak displacement (d ₀₀₁) was observed through the X-ray diffraction; this suggests the incorporation of charcoal into the clay lamellas and the formation of a new phase. Tests of adsorption with methylene blue dye were also carried out to evaluate the percentage of dye removal by the adsorbent, in which the composites presented better results than charcoal, indicating great potential for industrial use. A 2³ factorial design was employed to evaluate the influence of temperature, ionic strength and pH on the adsorption of methylene blue using the AV₅₀ composite that presented the best adsorption efficiency.     

Effect of graphitic carbon nitride powders on adsorption removal of antibiotic resistance genes from water

There is a growing need to eliminate antibiotic resistance genes (ARGs) in the environment and mitigate widespread antibiotic resistance. Graphitic carbon nitride (g-C₃N₄) was successfully synthesized via facile thermal polymerization approach and its potential for adsorption treatment of ARGs in water was examined. Batch adsorption experimental results revealed that g-C₃N₄ powders had robust adsorption activity for the gene ampC and ermB. Adsorption kinetics and isotherms were systematically investigated to explain the adsorption mechanism. The apparent adsorption equilibrium could be reached within 180 min. The adsorption process effectively removed ARGs (ampC and ermB) from water with 3.2 log and 4.2 log reductions, respectively. In addition, experimental data were analyzed by several models and simulated well with Langmuir isotherm and pseudo-second-order model. It indicated that adsorption process might be dominated by the chemical rate-limiting step. Moreover, the effects of temperature and pH on the removal of ARGs were conducted and the isoelectric point (IEP) was obtained. Finally, we have demonstrated that the g-C₃N₄ is a novel adsorbent and can be used as column packing to remove ARGs by filtration.     

Bifunctional activated carbon with dual photocatalysis and adsorption capabilities for efficient phenol removal

Bifunctional activated carbons (AC) with the abilities of both photocatalysis and adsorption were fabricated via the sol?Cgel route combined with hydrothermal treatment and N₂ reactivation method. TiO₂ was located mainly at the entrance of the surface macropores of AC. Under UV light irradiation, efficient removal of phenol was realized by combination of adsorption and photocatalytic degradation for the obtained bifunctional materials. In insufficient light or dark, phenol removal occurred mainly through adsorption. The prepared bifunctional carbon with a mass ratio of 50 TiO₂ per AC ratio exhibited high efficiency for phenol removal. The total phenol removal capacity of 50TiO₂/AC was almost 5 times of that of pure AC and 6 times of that pure TiO₂ after 10 cycles. The prepared bifunctional carbons possess the advantages of high pollutant removal capability and good recyclability, making them promising for the efficient treatment of lightly polluted aqueous solutions.     

Halogenated benzothiadiazole-based conjugated polymers as efficient photocatalysts for dye degradation and oxidative coupling of benzylamines

Donor-acceptor(D-A) conjugated polymers are widely used in photovoltaic applications and heterogeneous catalysis due to their tunable building block and pre-designable structures. Here, a series of adjustable Donor-acceptor(D-A) benzothiodiazole-based conjugated polymers were designed and synthesized. The photocatalytic performance could be improved by fine-tuning the chemical structure by halogen substitution(F or Cl). The polymers exhibited excellent optoelectronic properties and were effectiv...     

Synthesis of sulfhydryl-functionalized polymers for the efficient adsorption of Pd2+ and Ag+ from aqueous solution

Herein, two sulfhydryl-functionalized polymers, namely, EDT-HCPS and TMPMP-HCPS, were synthesized according to the Friedel-Craft s alkylation and nucleophilic substitution, and they were used to adsorb Pd²⁺ and Ag⁺ from aqueous solution. The Friedel-Crafts alkylation offered the polymers with hyper-cross-linking frameworks composed of plentiful rigid methylene. The nucleophilic substitution brought abundant functional  SH groups (the sulfur contents were 12.6 and 9.4 wt%, respectively) to the polymers. The adsorption results showed that the capacities of Pd²⁺ and Ag⁺ on EDT-HCPS were larger than TMPMP-HCPS, and the higher quantities of functional  SH groups and the porosity played a beneficial role. The equilibrium data can be characterized by the Langmuir model, and the maximum capacities of Pd²⁺ and Ag⁺ on EDT-HCPS at 308 K were predicted to be 383.92 and 212.93 mg g⁻¹, respectively. The produced polymers represented superior adsorption selectivity, reproducibility, and reusability, demonstrating their excellent performance for the adsorption of Pd²⁺ and Ag⁺, and analysis of the adsorption mechanism demonstrated that the  SH groups played a major role due to the strong chemical complexation of the functional  SH with Pd²⁺/Ag⁺.     

Manufacture of activated carbons using Egyptian wood resources and its application in oligothiophene dye adsorption

The following paper presents research on the conversion of wood wastes accessible in Egypt into activated carbon. In this study, wood samples of four Egyptian tree species were used: Delonix regia, Leucaena leucocephala, Salix mucronata, and Tipuana tipu. The wood scraps were soaked in a KOH solution and then carbonized at 600 °C under the flow of nitrogen; the resulting materials were analyzed by means of microscopic and spectroscopic techniques, low-temperature adsorption of nitrogen, and an investigation of the surface area using nitrogen sorption. The addition of a chemical activator facilitated an increase of the surface area up to 603 m² g⁻¹. In its second part, the work aims to experimentally confirm that synthesizing hybrid materials consisting of oligothiophene dye (OT) and the obtained activated carbon may contribute to improving the applicability of these carbons as dye adsorbents. Confocal microscopy, Raman spectra, and SEM-EDX microscopy were used to confirm the immobilization of oligomers on the surface of carbon hybrid materials. Confocal microscopy in particular is considered to be an appropriate technique of detecting the presence of adsorbed 6 T molecules on the carbon surface. The presented research is a major step towards the application of modified carbons as an attractive and inexpensive base for dye molecule adsorption.     

Geopolymeric adsorbents from fly ash for dye removal from aqueous solution

Adsorbents from coal fly ash treated by a solid-state fusion method using NaOH were prepared. It was found that amorphous aluminosilicate geopolymers would be formed. These fly ash-derived inorganic polymers were assessed as potential adsorbents for removal of some basic dyes, methylene blue and crystal violet, from aqueous solution. It was found that the adsorption capacity of the synthesised adsorbents depends on the preparation conditions such as NaOH:fly-ash ratio and fusion temperature with the optimal conditions being at 1.2:1 weight ratio of Na:fly-ash at 250-350 degrees C. The synthesised materials exhibit much higher adsorption capacity than fly ash itself and natural zeolite. The adsorption isotherm can be fitted by Langmuir and Freundlich models while the two-site Langmuir model producing the best results. It was also found that the fly ash derived geopolymeric adsorbents show higher adsorption capacity for crystal violet than methylene blue and the adsorption temperature influences the adsorption capacity. Kinetic studies show that the adsorption process follows the pseudo second-order kinetics.     

Fe3O4-CuO-activated carbon composite as an efficient adsorbent for bromophenol blue dye removal from aqueous solutions

Dye wastewater from industries is posing tremendous health hazards. The lethal dyes can be eliminated using nanomaterials and scientific approach like adsorption which is facile, cheap, safe as well as ecofriendly. Fe₃O₄-CuO-AC composite was prepared by a hydrothermal method and used for the removal of dyes in wastewater. The composite material was characterized by various techniques such as XRD, SEM, EDS, TEM and FT-IR. The Fe₃O₄-CuO-AC composite was used to treat five types of dyes in water. Fe₃O₄-CuO-AC composite showed the highest adsorption capability for bromophenol blue (BPB) dye. The effects of initial concentration, pH, the amount of adsorbent and temperature were also studied. The optimum conditions were found to be 20 ppm dye concentration, pH 9, an adsorbent dose of 0.06 gL^─1 at 65 °C. A removal efficiency of 97% was obtained for BPB dye during 120 min of adsorption. Kinetic studies indicated that a pseudo-second order is the most suitable model for the adsorption process. The Fe₃O₄-CuO-AC composite showed better adsorption capacity as compare to Fe₃O₄-AC except for the Methyl green dye. The maximum adsorption capacity was found to be 88.60 mg/g for BPB. Additionally, the thermodynamic parameters (ΔS°, ΔH° and ΔG°) showed that the process was spontaneous and exothermic. All the above results revealed that the Fe₃O₄-CuO-AC compositecan be an effective adsorbent for removing dyes from wastewater.     

Selective adsorption of the cationic dye rhodamine-6G from aqueous solution by phosphotungstic acid@MOF-199 composites

In this paper, H₃[ P(W₃O₁₀)₄]@MOF-199 composites ([email protected]) were successfully synthesized by a simple one-step reaction under solvothermal conditions and characterized by XRD, SEM, FT-IR and N₂ adsorption–desorption isotherms. Additionally, rhodamine-6G (Rh6G, a cationic dye) and methyl orange (MO, a anionic dye) as model dyes were employed to assess its adsorption performance. The adsorption capacity of MOF-199 towards Rh6G and MO were enhanced and weakened respectively after the introduction of PTA (from 8.6 mg/g to 41 mg/g; 11.4 mg/g to 2.6 mg/g) proving that the selective adsorption capacity for the cationic dye of porous MOF-199 could be improved through the modification of PTA. Moreover, in diverse initial concentrations of single Rh6G and MO aqueous solutions (10 mg/L, 25 mg/L, 50 mg/L and 100 mg/L), [email protected] exhibited much higher adsorbing capacity towards Rh6G (about 25, 30, 11 and 16 times higher than that of MO). In mixed dyes adsorption studies, the adsorption capacity of [email protected] towards Rh6G (2.871 mg) are nearly five times larger than that of MO (0.437 mg) even in a solution with a higher concentration of MO than Rh6G (5 mg/L of Rh6G and 10 mg/L of MO). The kinetic study indicated that the adsorption of the Rh6G and MO onto [email protected] followed the pseudo second-order model well. The isotherm obtained from experimental data fitted the Freundlich model (the linearly dependent coefficient are 0.99839 and 0.94845 for Rh6G and MO respectively) indicating multilayer adsorption mechanism. In summary, all these results implied that the as-prepared [email protected] is of great potential to be used as a cationic pollutants adsorbent with high efficiency and selectivity.     

Thiacalix[4]arene 1,2,3-triazole-polyethylene glycol polymers: Synthesis and dye adsorption properties

By reacting alkynylthiacalix[4]arenes with polyethylene glycol azido compounds, a series of novel thiacalix[4]arene 1,2,3-triazole-polyethylene glycol netty polymerswere conveniently prepared in good yields. Their structures and morphologies were studied by ¹H NMR, IR, and elemental analysis and SEM images. On average, approximately 28-31 thiacalixarene units exist in each polymeric molecule. These novel polymers possess excellent adsorption ability for both cationic and anionic dyes. The saturation adsorption capacity for Congo red reached 1.3-1.4 mmol/g. They exhibit high and stable adsorption ability in the scope of pH 5-9, and maintain good properties in five cycles.     

Pseudohalide-directed assemblies of Cu(II) coordination polymers with diverse structures and dye adsorption behaviors

Transition Metal Chemistry - Assembly of 3,4-bis(3-pyridyl)-5-(4-pyridyl)-1,2,4-triazole (L334) and CuBr2 without or with the presence of thiocyanate (SCN?)/dicyanamide [dca, N(CN)2?]...     

Application of zeolite MCM-22 for basic dye removal from wastewater

MCM-22 was employed as an effective adsorbent for removal of basic dyes including methylene blue, crystal violet, and rhodamine B from aqueous solution. The adsorption kinetics and isotherms were investigated. The adsorption capacity of MCM-22 for three dyes follows an order of MB > CV approximately RB. Kinetic studies indicate that the adsorption follows the pseudo second-order kinetics and the adsorption is a two-step diffusion process with film diffusion dominating the process. The adsorption isotherm can be well fitted by both the Langmuir and the Freundlich models. Thermodynamic calculations suggest that the adsorption of basic dyes on MCM-22 is an endothermic reaction.     

A simple and easily fabricated device for desorbing volatiles from porous polymers and other adsorbents

A device has been developed for the rapid desorption of organic compounds from adsorbent traps. Some advantages over previous devices include its ease of fabrication from inexpensive and readily obtainable materials, and its high portability between instruments. No major modification of the gas chromatograph (GC) inlet system is necessary and in a matter of seconds the desorber can be removed from the injection port for normal syringe injections. The adsorbent tubes can be transported into the field for sampling and returned to the laboratory for desorption and analysis by GC or GC-MS. Additionally, the device is useful for head space analysis, volatile organics analysis in aqueous solutions, and impurities in gaseous feed streams.     

Efficient removal of boron acid by N-methyl-D-glucamine functionalized silica-polyallylamine composites and its adsorption mechanism

A novel boron adsorbent was fabricated by grafting a boric acid chelating group, i.e., N-methyl-D-glucamine, onto the hydrophilic silica-polyallylamine composites (SPC). The boron adsorbent was characterized by scanning electron microscopy (SEM) and TGA method. The adsorption experiment indicated a maximum boron load capacity of ca. 1.55 mmol g(-1). The high load capacity was attributed to specific chemical affinity and physical adsorption. Highly effective removal of boric acid from aqueous solution was observed for the adsorbent even in the synthetic seawater containing high concentration of foreign ions. Analysis of adsorption thermodynamic and kinetics revealed a spontaneous sorption process that is driven by enthalpy change and limited by chemical reaction. The exhausted adsorbent was regenerated for repeated use by treating with 3% HCl solution, followed by neutralizing with 3% NH(3)·H(2)O at ambient temperature. Only 7% capacity loss was observed after five continuous adsorption-regeneration cycles.     

New carbon-carbonaceous composites for catalysis and adsorption

Properties, structural features, and basic principles for the synthesis of some new carbon-carbonaceous composite materials (CCM) originating at the Boreskov Institute of Catalysis are discussed. The CCM are synthesized via chemical growth of carbon deposits in a pre-formed porous carbon matrix. Among the CCM are: Sibunit produced by supporting pyrocarbon (PC) on carbon black granules, carbon filaments (CFC) produced by decomposition of CH₄ over Ni or Ni–Cu catalysts, CFC on Sibunit, CFC on ultradispersed diamond, and systems such as CFC/CFC, PC/CFC, etc. Basic mechanisms of structure and texture formation of CCM and some of their properties as adsorbents and catalyst supports are reported.     

Conversion of teak wood waste into microwave-irradiated activated carbon for cationic methylene blue dye removal: Optimization and batch studies

The objective of this study is to find optimum preparation conditions in converting teak wood waste into activated carbon (TWAC) and to evaluate its performance in adsorbing cationic dye of methylene blue (MB). TWAC was produced via physiochemical activation (potassium hydroxide, KOH chemical treatment, and carbon dioxide, CO₂ gasification) and heated through microwave irradiation technique. With the aid of response surface methodology (RSM), optimized TWAC was successfully synthesized at radiation power, radiation time, and impregnation ratio (IR) of 366 W, 5.30 min, and 1.15 g/g, respectively. These preparation conditions produced TWAC with MB adsorption uptakes of 66.69 mg/g and a yield of 38.23%. Characteristics of TWAC in terms of BET surface area, mesopores surface area, total pore volume, and average pore diameter were determined to be 1345.25 m²/g, 878.63 m²/g, 0.6140 cm³/g, and 2.85 nm, respectively. Isotherm studies divulged that the MB-TWAC adsorption system followed the Langmuir model with a maximum monolayer adsorption capacity of 567.52 mg/g. In terms of kinetic studies, this adsorption system fit pseudo-second order model the best whereas Boyd plot confirmed that the adsorption process was controlled by the film diffusion mechanism. Thermodynamic parameters of enthalpy change, ΔH°, entropy change, ΔS°, Gibbs free energy, ΔG° and Arrhenius activation energy, E_a were calculated to be ?4.06 kJ/mol, 0.06 kJ/mol.K, –22.69 kJ/mol and 16.03 kJ/mol, respectively. The activation and microwave heating methods employed succeeded to produce TWAC with excellent adsorption performance in removing MB dye. TWAC was also successfully regenerated for 5 cycles via microwave heating technique.     

Aqueous and gaseous adsorption from montmorillonite-carbon composites and from derived carbons

Clay-carbon composites and the carbons derived from demineralization of the clay template were examined for their aqueous adsorption properties (2,4,6-trichlorophenol and methylene blue) and for their gas adsorption/separation abilities regarding CO(2), CH(4), and N(2) gases. The sorption results are discussed in relation with their structural properties (surface area, pore width and volume, and surface chemistry). It was found that the properties of the adsorbents depend highly on the synthetic route, for instance, on the use of clay or H(2)SO(4) as structure mediating and activating agents, respectively. Particularly, the simultaneous use of clay and H(2)SO(4) leads to a synergistic action, which imparts to the final solids the highest sorption capacity and the best potential for separation of CO(2) from gaseous mixtures of CH(4) and N(2).