Adsorption of dyes on multifunctionalized nano-silica KCC-1

Dendritic mesoporous nanoparticles for the detection, adsorption, and degradation of hazardous substances in the environment: State-of-the-art and future prospects

Equipped with hierarchical pores and three-dimensional (3D) center-radial channels, dendritic mesoporous nanoparticles (DMNs) make their pore volumes extremely large, specific surface areas super-high, internal spaces especially accessible, and so on. Other entities (like organic moieties or nanoparticles) can be modified onto the interfaces or skeletons of DMNs, accomplishing their functionalization for desirable applications. This comprehensive review emphasizes on the design and construction of DMNs-based systems which serve as sensors, adsorbents and catalysts for the detection, adsorption, and degradation of hazardous substances, mainly including the construction procedures of brand-new DMNs-based materials and the involved hazardous substances (like industrial chemicals, chemical dyes, heavy metal ions, medicines, pesticides, and harmful gases). The sensitive, adsorptive, or catalytic performances of various DMNs have been compared; correspondingly, the reaction mechanisms have been revealed strictly. It is honestly anticipated that the profound discussion could offer scientists certain enlightenment to design novel DMNs-based systems towards the detection, adsorption, and degradation of hazardous substances, respectively or comprehensively.

Hydrophilic magnetic Ti3C2Tx-based nanocomposite as an efficient boron adsorbent: Synthesis, characterization, and application

It is widely recognized that wastewater containing boron is an environmental issue. Therefore, the development of adsorbents with excellent adsorption capacity, stability, and recyclability is essential in water treatment applications. A Fe3O4/PDA/Ti3C2Tx/PEI/DHHA nanocomposite has been prepared that can be used to separate and recover boric acid by adjusting the pH of the solution, based on the affinity theory of boric acid and cis-diol. Through series characterization, it was determined that the adsorbent possessed good magnetic properties, high hydrophilicity and high loading capacities. In this study, 4-formylphenylboronic acid (FPBA) was selected as the model compound. The nanocomposite exhibited an adsorption equilibrium time of 10 h and an adsorption capacity of 98.99 mg/g at pH = 8.5 and 25 °C. The Langmuir isothermal model and the quasi-secondary kinetic model are both appropriate for describing the adsorption process. Thermodynamic results suggest that adsorption is a spontaneous chemisorption process. Furthermore, the nanocomposite retains good regeneration performance after five adsorption-desorption cycles.

Methylene blue removal from aqueous solutions using a biochar/gellan gum hydrogel composite: Effect of agitation mode on sorption kinetics

Hydrogel membranes are prepared by casting a mixture of gellan gum (associated with PVA) and biochar produced from a local Egyptian plant. The mesoporous material is characterized by a specific surface area close to 134 m² g^-1, a residue of 28 % (at 800 °C), and a pH_PZC close to 6.43. After grinding, the material is tested for Methylene Blue sorption at pH 10.5: sorption capacity reaches 1.70 mmol MB g^-1 (synergistic effect of the precursors). The sorption isotherms are fitted by both Langmuir and Sips eqs. MB sorption increases with temperature: the sorption is endothermic (∆H°: 12.9 kJ mol^-1), with positive entropy (∆S°: 125 J mol^-1 K^-1). Uptake kinetics are controlled by agitation speed (optimum ≈200 rpm) and resistance to intraparticle diffusion. The profiles are strongly affected by the mode of agitation: the equilibrium time (≈180 min) is reduced to 20-30 min under sonication (especially at frequency: 80 kHz). The mode of agitation controls the best fitting equation: pseudo-first order rate agitation for mechanical agitation contrary to pseudo-second order rate under sonication. The sorption of MB is poorly affected by ionic strength (loss <6 % in 45 g L^-1 NaCl solution). Desorption (faster than sorption) is completely achieved using 0.7 M HCl solution. At the sixth recycling, the loss in sorption is close to 5 % (≈ decrease in desorption efficiency). The process is successfully applied for the treatment of MB-spiked industrial solution: the color index decreases by >97 % with a sorbent dose close to 1 g L^-1; a higher dose is required for maximum reduction of the COD (60 % at 3 g L^-1).

Hexamethylenetetramine functionalized graphene oxide-alginate beads nanocomposite as efficient sorbent for dye from aqueous solution

In this study, a novel eco-friendly sorbent, hexamethylenetetramine (HMTA) functionalized calcium alginate (AG) immobilized graphene oxide (GO) composite (AG-GO-HMTA) and hexamethylenetetramine functionalized calcium alginate composite (AG-HMTA) were prepared. Adsorption factors including pH impact, contact time, initial dye concentration, dosage, selectivity and reusability on methylene blue (MB) removal from water were investigated. The prepared sorbents were characterized using structural (e.g. XRD, FT-IR, EDAX), thermal (e.g. TGA, DTG), and morphological (e.g. SEM, BET) analysis techniques. The equilibrium adsorption data was described by the Langmuir and Freundlich isotherms, and the adsorption kinetic and thermodynamic parameters were investigated. The field studies and regeneration of the beads were investigated. AG-GO HMTA displays a well-defined porous structure and this desired morphology arising from high quality dispersion of HMTA within the AG-GO matrix. The highest adsorption capacities were observed at pH ∼ 5, meanwhile the adsorption of MB dye molecules, positively charged, onto the beads became faster due to strong electrostatic interactions. When the value of dosage is 0.01 g, the equilibrium concentration (mg/g) are maximum at 103, 110, 164, 168 mg/g for AG, AG-GO, AG-HMTA and AG-GO-HMTA, respectively. The present work shows that pseudo first order could describe the MB adsorption onto AG while it couldn't describe the MB adsorption onto the functionalized sorbents due to the hybrid materials complicity.

Progress in Hybridization of Covalent Organic Frameworks and Metal-Organic Frameworks

Metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) hybrid materials are a class of porous crystalline materials that integrate MOFs and COFs with hierarchical pore structures. As an emerging porous frame material platform, MOF/COF hybrid materials have attracted tremendous attention, and the field is advancing rapidly and extending into more diverse fields. Extensive studies have shown that a broad variety of MOF/COF hybrid materials with different structures and specific properties can be synthesized from diverse building blocks via different chemical reactions, driving the rapid growth of the field. The allowed complementary utilization of π-conjugated skeletons and nanopores for functional exploration has endowed these hybrid materials with great potential in challenging energy and environmental issues. It is necessary to prepare a "family tree" to accurately trace the developments in the study of MOF/COF hybrid materials. This review comprehensively summarizes the latest achievements and advancements in the design and synthesis of MOF/COF hybrid materials, including COFs covalently bonded to the surface functional groups of MOFs (MOF@COF), MOFs grown on the surface of COFs (COF@MOF), bridge reaction between COF and MOF (MOF+COF), and their various applications in catalysis, energy storage, pollutant adsorption, gas separation, chemical sensing, and biomedicine. It concludes with remarks concerning the trend from the structural design to functional exploration and potential applications of MOF/COF hybrid materials.

Safranin-O cationic dye removal from wastewater using carboxymethyl cellulose-grafted-poly(acrylic acid-co-itaconic acid) nanocomposite hydrogel

Copolymer of acrylic acid (AA) and itaconic acid (IA) grafted onto sodium carboxymethyl cellulose hydrogel (CMC-g-poly (AA-co-IA)) was successfully synthesized as an adsorbent to remove safranin-O from wastewater. The swelling and removal efficiencies of CMC-g-poly (AA-co-IA) were enhanced by increasing IA/AA molar ratio as well as by incorporation of montmorillonite clay nano-sheets (MMT). The surface area of MMT, CMC-g-poly (AA-co-IA), and CMC-g-poly (AA-co-IA) samples was 15.632, 0.61452, and 0.66584 m²/g, respectively, indicating the effectiveness of MMT nano-sheets in improving hydrogel surface area. The maximum removal efficiency of CMC-g-poly (AA-co-IA)/MMT under optimum conditions i.e., pH of 8, initial concentration of 10 mg/L, adsorbent dose of 2 g/L, and contact time of 40 min was ascertained 99.78% using a response surface methodology-central composite design (RSM-CCD). Pseudo-second-order and Langmuir models giving the maximum monolayer adsorption capacity of 18.5185 mg/g and 19.1205 mg/g for CMC-g-poly (AA-co-IA) and CMC-g-poly (AA-co-IA)/MMT samples, respectively are the best-fitted models for kinetic and equilibrium data. Thermodynamically, safranin-O decontamination was spontaneous, exothermic, and entropy decreasing. Moreover, ad (de)sorption behavior study showed that CMC-g-poly (AA-co-IA)/MMT performance was not changed after multiple recovery steps. Therefore, CMC-g-poly (AA-co-IA)/MMT was considered as a highly potential adsorbent for safranin-O removal from wastewater.

Selective capture of Pd(II) from aqueous media by ion-imprinted dendritic mesoporous silica nanoparticles and re-utilization of the spent adsorbent for Suzuki reaction in water

The development of highly efficient adsorptive material for the selective capture of Pd(II), and re-utilization of spent Pd(II)-loaded adsorbent as an efficient catalyst for organic synthesis are of great significance, but challenging. Particularly, the heterogeneous palladium-catalyzed Suzuki reaction in aqueous media is much more challenging than that of homogeneous. Herein, several novel Pd(II) ion-imprinted polymers (PIIPs) based on dendritic fibrous silica particles are constructed by surface ion imprinting technology (SIIT), using Schiff base and pyridine groups functionalized organosilicon as functional monomer. The PIIP-3 prepared by 3 g of functional monomer exhibits the best adsorption performance, and shows ultrafast (10 min) and selective capture of Pd(II) with high uptake capacity (382.5 mg/g). Moreover, the waste Pd(II) loaded PIIP-3 (PIIP-3-Pd) can serve as a catalyst towards the Suzuki reaction in water, affording 94.2 % yield of the desired product. Interestingly, the PIIP-3-Pd can be reused 12 times without an appreciable decrease in catalytic activity, which is probably due to the imprinted cavity and specific recognition site of PIIP-3 can match and recapture Pd active species in a complex catalytic environment. Thus, this work demonstrates huge potentials of SIIT to enhance the selectivity of adsorption process and increase the lifetime of catalysts.

Simultaneous removal of Pb2+ and direct red 31 dye from contaminated water using N-(2-hydroxyethyl)-2-oxo-2H-chromene-3-carboxamide loaded chitosan nanoparticles

This study reports the preparation of a new material that can remove synthetic dyes and trace metals simultaneously. A new coumarin derivative was synthesized and its chemical structure was inferred from spectral data (FT-IR, ¹H-NMR, ¹³C-NMR). Meanwhile, chitosan nanoparticles (CsNPs) were prepared then used as a carrier for two different concentrations of the coumarin derivative (C1@CsNPs and C2@CsNPs). The TEM, SEM and DLS findings illustrated that the prepared nanocomposites exhibited spherical shape and small size (less than 200 nm). The performance of the prepared material for the removal of an anionic dye (direct red 31, DR31) and cationic trace metal (Pb²⁺) was evaluated in unary and binary systems. The results revealed that complete removal of 10 mg L⁻¹ of DR31 and Pb²⁺ in unary system was achieved at pH_o 3.0 and 5.5 using 0.5 and 2.0 g L⁻¹, respectively, of C2@CsNPs. The adsorption of DR31 and Pb²⁺ followed different mechanisms as deduced from the effect of pH_o, kinetic, isotherm and binary adsorption studies. The adsorption of DR31 followed the Langmuir isotherm model and the pseudo-first-order kinetic model. While, the adsorption of Pb²⁺ followed Freundlich isotherm model and Elovich kinetic model. In the binary system, the co-presence of DR31 and Pb²⁺ did not affect the adsorption of each other's. Overall, the prepared material showed promising results for the removal of anionic dyes and cations trace metals from contaminated water.

This study reports the preparation of a new material that can remove synthetic dyes and trace metals simultaneously.

Highly Selective Removal of Cationic Dyes from Wastewater by MgO Nanorods

The organic synthetic dyes employed in industries are carcinogenic and harmful. Dyes must be removed from wastewater to limit or eliminate their presence before dumping into the natural environment. The current study aims to investigate the use of MgO nanoparticles to eliminate basic fuchsine (BF), as a model cationic dye pollutant, from wastewater. The MgO nanorods were synthesized through a coprecipitation method. The obtained nanocomposite was characterized using various techniques such as X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Brunauer–Emmett–Teller (BET), and FTIR spectroscopy. It was found that the variation of dye concentration and pH influenced the removal of BF by MgO. The adsorption capacity of 493.90 mg/g is achieved under optimum operating conditions (pH = 11, contact time = 236 min, and initial BF concentration = 200 ppm). Pseudo-second-order adsorption kinetics and Freundlich isotherm models best fitted BF sorption onto MgO nanorods. The BF sorption mechanism is associated with the electrostatic attractions and hydrogen bond between the O–H group of MgO and the NH₂ groups of BF, as indicated by the pH, isotherms, and FTIR studies. The reusability study indicates that MgO was effectively used to eliminate BF in at least four continuous cycles. The investigation of MgO with different dyes suggests the high adsorption selectivity of BF, crystal violet (CV), and malachite green (MG) dyes compared with methyl orange (MO) dye. Overall, MgO nanorods can act as a potential and promising adsorbent for the efficient and rapid removal of cationic dyes (CV, MG, and BF) from wastewater.

Neural-based modeling adsorption capacity of metal organic framework materials with application in wastewater treatment

We developed a computational-based model for simulating adsorption capacity of a novel layered double hydroxide (LDH) and metal organic framework (MOF) nanocomposite in separation of ions including Pb(II) and Cd(II) from aqueous solutions. The simulated adsorbent was a composite of UiO-66-(Zr)-(COOH)2 MOF grown onto the surface of functionalized Ni50-Co50-LDH sheets. This novel adsorbent showed high surface area for adsorption capacity, and was chosen to develop the model for study of ions removal using this adsorbent. A number of measured data was collected and used in the simulations via the artificial intelligence technique. Artificial neural network (ANN) technique was used for simulation of the data in which ion type and initial concentration of the ions in the feed was selected as the input variables to the neural network. The neural network was trained using the input data for simulation of the adsorption capacity. Two hidden layers with activation functions in form of linear and non-linear were designed for the construction of artificial neural network. The model's training and validation revealed high accuracy with statistical parameters of R2 equal to 0.99 for the fitting data. The trained ANN modeling showed that increasing the initial content of Pb(II) and Cd(II) ions led to a significant increment in the adsorption capacity (Qe) and Cd(II) had higher adsorption due to its strong interaction with the adsorbent surface. The neural model indicated superior predictive capability in simulation of the obtained data for removal of Pb(II) and Cd(II) from an aqueous solution.

Porous organic-inorganic hybrid materials for catalysis, energy and environmental applications

Introduction of organic functionalities into the porous inorganic materials make the resulting hybrid porous framework not only more flexible and hydrophobic, but also provide additional scope for further functionalization, which...