Core-shell Fe3O4@zeolite NaA as an Adsorbent for Cu2

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

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

Biochar Derived from Chinese Herb Medicine Residues for Rhodamine B Dye Adsorption

In this study, one well-known CHM residue (Atropa belladonna L., ABL) was used to prepare biochar capable of adsorbing rhodamine B (RhB) with an ultrahigh surface area for the first time. Three micropore-rich ABL biochars including ABL@ZnCl₂ (1866 m²/g), ABL@H₃PO₄ (1488 m²/g), and ABL@KOH (590 m²/g) were obtained using the one-step carbonization method with activation agents (ZnCl₂, H₃PO₄, and KOH) via chemical activation and carbonization at 500 °C, and their adsorption performance for RhB was systematically studied with adsorption kinetics, isotherms, and thermodynamics. Through pore diffusion, π-π interaction, and hydrogen bonding, ABL biochar had excellent adsorption performance for RhB. Moreover, when C ₀ was 200 mg/L, biochar dosage was 1 g/L, and the contact time was 120 min; the maximum RhB adsorption capacity and removal efficiency on ABL@ZnCl₂ and ABL@H₃PO₄ were 190.63 mg/g, 95% and 184.70 mg/g, 92%, respectively, indicating that it was feasible to prepare biochar from the ABL residue for RhB adsorption. The theoretical maximum adsorption capacities of ABL@ZnCl₂ and ABL@H₃PO₄ for RhB were 263.19 mg/g and 309.11 mg/g at 25 °C, respectively. Furthermore, the prepared biochar showed good economic applicability, with pay back of USD 972/t (ABL@ZnCl₂) and USD 987/t (ABL@H₃PO₄), respectively. More importantly, even after five cycles, ABL@H₃PO₄ biochar still showed great RhB removal efficiency, suggesting that it had a good application prospect and provided a new method for the resource utilization of traditional CHM residues. Additionally, pore diffusion, π-π interactions, and hydrogen bonding all play roles in the physical adsorption of RhB on ABL biochar. π-π interactions dominated in the early stage of RhB adsorption on ABL@H₃PO₄, while pore diffusion played a crucial role in the whole adsorption process on both adsorbents.

Multilayer Graphene Oxide Supported ZIF-8 for Efficient Removal of Copper Ions

To address the performance deterioration of ZIF-8 for the adsorption of copper ions caused by powder volume pressure and particle aggregation, we employed multilayer graphene oxide (MGO) as a support to prepare composite adsorbents (MGO@ZIF-8) by using the in situ growth of ZIF-8 on MGO. Due to a good interfacial compatibility and affinity between ZIF-8 and graphene nanosheets, the MGO@ZIF-8 was successfully prepared. The optimal Cu²⁺ adsorption conditions of MGO@ZIF-8 were obtained through single factor experiments and orthogonal experiments. Surprisingly, the Cu²⁺ adsorption capacity was significantly improved by the integration of MGO and ZIF-8, and the maximum Cu²⁺ adsorption capacity of MGO@ZIF-8 reached 431.63 mg/g under the optimal adsorption conditions. Furthermore, the kinetic fitting and isotherm curve fitting confirmed that the adsorption law of Cu²⁺ by MGO@ZIF-8 was the pseudo-second-order kinetic model and the Langmuir isotherm model, which indicated that the process of Cu²⁺ adsorption was monolayer chemisorption. This work provides a new approach for designing and constructing ZIF-8 composites, and also offers an efficient means for the removal of heavy metals.

Sonochemical Preparation of a Magnet-Responsive Fe3O4@ZIF-8 Adsorbent for Efficient Cu2+ Removal

This work presents a novel approach to synthesizing magnetic core-shell nanocomposites, consisting of magnetic nanoparticles and a metal-organic framework, for environmental applications. The synthesis is based on the encapsulation of magnetic Fe₃O₄ nanoparticles with microporous zeolitic imidazolate framework-8 (ZIF-8) nanocrystals via ultrasonic activation under a continuous supply of precursor solutions. This sonochemical approach is proven to be a fast, cost-effective, and controllable route for the preparation of magnet-responsive Fe₃O₄@ZIF-8 nanoparticles with a core-shell structure. The functional nanomaterial possesses a high content of ZIF-8 and combined micro/mesoporosity, and thus can be used as adsorbents that can be easily separated using a magnet. In particular, the sonochemically prepared Fe₃O₄@ZIF-8 exhibits significant adsorption performance for the removal of copper ions from water: a short adsorption time (10 min), high maximum uptake capacity (345 mg g⁻¹), and excellent removal efficiency (95.3%). These performances are interpreted and discussed based on the materials characteristics of Fe₃O₄@ZIF-8 established by microscopy, gas sorption, X-ray diffraction, and thermal analysis.

Nanoarchitectonics for High Adsorption Capacity Carboxymethyl Cellulose Nanofibrils-Based Adsorbents for Efficient Cu2+ Removal

In the present study, carboxymethyl cellulose nanofibrils (CMCNFs) with different carboxyl content (0.99-2.01 mmol/g) were prepared via controlling the ratio of monochloroacetic acid (MCA) and sodium hydroxide to Eucalyptus bleached pulp (EBP). CMCFs-PEI aerogels were obtained using the crosslinking reaction of polyethyleneimine (PEI) and CMCNFs with the aid of glutaraldehyde (GA). The effects of pH, contact time, temperature, and initial Cu2+ concentration on the Cu2+ removal performance of CMCNFs-PEI aerogels was highlighted. Experimental data showed that the maximum adsorption capacity of CMCNF30-PEI for Cu2+ was 380.03 ± 23 mg/g, and the adsorption results were consistent with Langmuir isotherm (R2 > 0.99). The theoretical maximum adsorption capacity was 616.48 mg/g. After being treated with 0.05 M EDTA solution, the aerogel retained an 85% removal performance after three adsorption-desorption cycles. X-ray photoelectron spectroscopy (XPS) results demonstrated that complexation was the main Cu2+ adsorption mechanism. The excellent Cu2+ adsorption capacity of CMCNFs-PEI aerogels provided another avenue for the utilization of cellulose nanofibrils in the wastewater treatment field.

A lamellar structure zeolite LTA for CO2 capture

Two-dimensional zeolite LTA with a special structure can be used in gas separation.

Controllable Preparation of Cubic Zeolite A and Application of Langmuir Model in Carbon Dioxide Adsorption

A large amount of remaining fly ash has been piled up or landfilled, which not only a waste of land resources but also results in a series of environmental problems. Therefore, using fly ash to produce high value-added products is a win-win development orientation between human beings and nature. In this study, zeolite A is successfully synthesized using a hydrothermal method using fly ash. Additionally, it is at 1.0 mol·L⁻¹ of the alkali concentration that the crystallinity of zeolite A reaches the maximum value, about 96.6%. FTIR research shows that the main secondary structural unit D4R vibration band of zeolite A appears at 555 cm⁻¹. The results of the SEM study indicate the structure of zeolite A is cubic. The TEM results show that the crystal structure of the zeolite A belongs to the body-centered cubic structure. Meanwhile, the positively charged sodium ions cooperate with the silicon oxygen tetrahedron and the aluminum oxygen tetrahedron to form the zeolite A skeleton. Carbon dioxide adsorption equilibrium study shows that the maximum adsorption capacity of zeolite A of 46.5 mL·g⁻¹ is significantly higher than the maximum adsorption capacity of commercial-grade zeolite 4A of 39.3 mL·g⁻¹. In addition, the application of the Langmuir model in the adsorption of carbon dioxide by commercial-grade zeolite 4A and zeolite A is studied, which not only extends the application of zeolite A, but can be further extended to other zeolite materials as well. Meanwhile, the adsorption process belongs to the Langmuir model, which is a single layer adsorption on an ideal surface.