Neodymium/zirconium bimetallic metal–organic framework for heavy rare earth lutetium(iii): adsorption performance and mechanism study

The adsorption and separation of gases are important for mitigating the greenhouse effect, popularizing clean energy and treating volatile organic compounds (VOCs). Metal organic frameworks (MOFs) have been attracted broad attention due to their high specific surface area, adjustable pore structure and surface functionality. MOFs have been widely applied in gas adsorption and separation. The drawbacks of some MOFs are the high humidity sensitivity and poor thermal stability that hinder their industrial applications. Porous carbon materials possess high specific surface area, exceptional chemical and thermal stabilities. Porous carbon materials derived from MOFs as precursors not only overcome the shortcomings of some MOFs with poor water and thermal stabilities, but also retain the advantages of MOFs materials effectively. MOFs-derived porous carbon materials have good application prospects in gas adsorption and separation. This paper introduces the research status of MOFs-derived porous carbon materials, and focuses on their applications in the field of gas adsorption and separation. Synthesis methods for MOFs-derived porous carbon materials mainly include direct carbonization, carbonization with additional precursor and chemical activation. Specific surface area, pore size and surface functional groups of MOFs-derived porous carbon materials have great impact on their adsorption and separation performances for gases (carbon dioxide, hydrogen and volatile organic compounds). In general, MOFs-derived porous carbon materials with high surface area could exhibit excellent adsorption performance for CO2. And the pore size characteristics of MOFs-derived porous carbon materials play important roles in the adsorption capacity and diffusion rate of CO2. Nitrogen doping can improve CO2 adsorption capacities owing to Lewis acid-base interaction, electrostatic interaction and hydrogen bonding between the surface functional groups of MOFs-derived porous carbon materials and CO2. Furthermore, H2 storage is primarily determined by the narrow micropore, and chemical doping can effectively promote H2 storage of MOFs-derived porous carbon materials. In addition, VOCs adsorption is associated with the physiochemical characters of adsorbents (e.g., specific surface area, pore size, pore volume, surface chemical functional groups), properties of adsorbates (e.g., molecular weight, molecular structure, polarity, and boiling point) as well as the adsorption conditions (e.g., temperature and humidity). However, the researches on MOFs-derived porous carbon materials in gas adsorption and separation still face many challenges. (1) The pore structure, morphology and surface chemical properties of MOFs-derived porous carbon materials are directly affected by various factors, such as types of MOFs, types and amounts of additional carbon sources or additional nitrogen sources, carbonization temperature, time and atmosphere, types and ratios of activators, activation temperature and time, chemical doping and so on. (2) There are rare studies on the adsorption mechanism of MOF-derived porous carbon materials for various gases, the multi-component competitive adsorption mechanism, and the influence of environmental factors (such as environmental temperature and humidity) on the adsorption performance. (3) Environmental pollution will be caused during the chemical activation process of MOFs-derived porous carbon materials. At present, there are few reports on the recovery of pyrolysis gases and dispose of the generated waste during the activation process. (4) There is an urgent need to develop new synthetic methods for MOFs-derived porous carbon materials to achieve large-scale production. In a word, the related researches of MOFs-derived porous carbon materials can not only expand the application range of MOFs materials, but also promote the development of gas adsorption and separation. We believe that the application of MOFs-derived porous carbon materials in the field of gas adsorption and separation will make great breakthrough in the future.

Novel Al-doped UiO-66-NH2 nanoadsorbent with excellent adsorption performance for tetracycline: Adsorption behavior, mechanism, and application potential

Tuned bimetallic MOFs with balanced adsorption and non-radical oxidizing activities for efficient removal of arsenite

Adsorption performance and mechanism of TiO2/PVDF-based lithium-ion imprinted membrane in leaching solution of spent lithium-ion batteries

Magnetic biochar (MBC) has the advantages including wide source of raw materials and low cost, and has become a potential adsorbent for water treatment, overcoming the shortcomings of biochar (BC) with the hard separation of solid and liquid. Peanut hull-derived magnetic biochar loaded with Fe3O4 (Fe3O4/BC) was prepared by co-precipitation method. By means of material characterization and batch processing experiments, material properties and environmental factors affecting adsorption performance were investigated. The adsorption mechanism of Fe3O4/BC on malachite green (MG) was revealed using adsorption isotherms, adsorption kinetics and thermodynamics. The results showed that Fe3O4 particles were uniformly loaded, the total pore volume was increased, surface oxygen-containing functional groups were formed, and the maximum adsorption capacity of the biochar reached 175.4 mg g−1, 1.6 times of that before modification. In a wide PH range, Fe3O4/BC showed high adsorption performance for MG, and significant influence from ionic strength wasn’t found. Chemical adsorption was the main adsorption mechanism, including electrostatic interaction, cation exchange, hydrogen bonding and π-π interaction. The study of adsorption mechanism will promote the application of MBC in the removal of organic pollutants from water.

Magnetic graphene oxide nanocomposite: One-pot preparation, adsorption performance and mechanism for aqueous Mn(Ⅱ) and Zn(Ⅱ)

High-performance Hf/Ti-doped defective Zr-MOFs for cefoperazone adsorption: Behavior and mechanisms

A potential lignocellulosic biomass based on banana waste for critical rare earths recovery from aqueous solutions

Widespread environmental pollution caused by the misuse of tetracyclines (TCs) has become a global issue, necessitating the development of water treatment materials for antibiotic removal. Magnetic biochar (MBC) possesses several advantages, including a wide range of raw material sources and low cost, making it a potential adsorbent that overcomes the limitations of biochar (BC) regarding solid–liquid separation. In this study, peanut shell-derived magnetic biochar loaded with Fe3O4 (Fe3O4/BC) was prepared to study its adsorption performance and environmental factors for TCs. The adsorption mechanism was revealed using adsorption isotherms, adsorption kinetics and thermodynamics. The results showed that the total pore volume was increased, and surface oxygen-containing functional groups were formed of that before BC modification. In a wide pH range, Fe3O4/BC showed high adsorption performance for TCs, with an adsorption rate of over 85%. Chemical adsorption was the main adsorption mechanism, including hydrogen bonding, as well as π-π interactions, electrostatic interactions, intrapore diffusion and hydrophobic interactions. Moreover, reusability and obtaining cost of the material were analyzed, demonstrating its promising application prospects. This study will promote the application of Fe3O4/BC in the removal of antibiotics pollutants from water.

In this study, the magnetic reduced graphene oxide (RGO/Fe3O4), with easy separation and high adsorption performance, was prepared and used to treat glyphosate (GLY) contaminated water. GLY adsorption performance of RGO/Fe3O4 was investigated, and influences of pH, adsorption time, temperature, contaminant concentration, and competing anions were analyzed. Moreover, the adsorption mechanism was discussed in the light of several characterization methods, including scanning electron microscopy (SEM), energy dispersive spectrum (EDS), Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The results demonstrated that the RGO/Fe3O4 presented a significant GLY adsorption capacity and acid condition was beneficial for this adsorption. The pseudo-second-order kinetic model and the Langmuir model correlated satisfactorily to the experimental data, indicating that this process was controlled by chemical adsorption and monolayer adsorption. Thermodynamic studies revealed that the adsorption of glyphosate onto RGO/Fe3O4 was spontaneous, endothermic, and feasible process. High temperatures were beneficial to GLY adsorption. The GLY adsorption mechanism of RGO/Fe3O4 was mainly attributed to hydrogen-bond interaction, electrostatic interaction, and coordination. Therefore, the RGO/Fe3O4 investigated in this research may offer an attractive adsorbent candidate for treatment of glyphosate contaminated water and warrant further study as a mechanism for glyphosate efficient removal.

The development of widely sourced and efficient adsorbents is crucial for the adsorption of lead from wastewater. A novel adsorbent, N-doped weathered coal (NWC), was prepared in this study using weathered coal as the precursor and triethylenetetramine (TETA) as the N-source. The adsorption performance and behavior of Pb(II) on NWC were investigated using batch adsorption experiments. The results demonstrated that NWC has an efficient adsorption performance towards Pb(II), with a maximum monolayer adsorption capacity of 216.32 mg g−1 (25 °C). The adsorption process was spontaneous and endothermic, and the importance of chemisorption was observed. The adsorption mechanisms of NWC were also analyzed based on its physicochemical structure before and after the Pb(II) adsorption and desorption experiments. The N and O functional groups, acting as electron donors, promoted coordination with Pb(II), making complexation the dominant mechanism. Its contribution to the adsorption mechanism could reach 44.81%. NWC is a promising material for both wastewater treatment and the resource utilization of weathered coal.

Nitrate pollution in water bodies has become a global environmental problem, and its excessive presence not only leads to eutrophication of water bodies but also threatens human health through the drinking water pathway. Therefore, it is urgent to develop new adsorbents with high adsorption capacity, good selectivity and excellent regeneration performance to solve the problem of nitrate pollution. In this study, reed straw (RS), trimethylamine-modified reed straw (MRS) and triethylamine-modified reed straw (ERS) were prepared by quaternary amination modification for nitrate removal. The adsorption performance, desorption performance, adsorption characteristics under disturbed environment and dynamic adsorption performance were investigated experimentally, and the adsorption mechanism was analyzed by various characterization means. The adsorption performance followed the order ERS (12.25 mg·g−1) > MRS > RS, demonstrating that quaternary amination modification, particularly with triethylamine, significantly enhanced the NO3−-N adsorption capacity. ERS exhibited excellent regeneration stability (over 80% after nine cycles) and high selectivity towards NO3−-N in the presence of competing anions (Cl−, SO42−, humic acid). In the dynamic adsorption experiment, ERS had a breakthrough time of 290 min at a packing height of 3.3 cm, with an adsorption capacity of 10.74 mg·g−1 and good adaptability to flow rate. In the actual wastewater application, the initial NO3−-N removal rate was over 95%, the dynamic desorption rate reached 99.2% and the peak nitrate concentration of the desorbed solution reached 27 times of the initial value, confirming its high efficiency regeneration and enrichment ability. The study shows that the amine-modified reed straw adsorbent has a good potential for application and provides a new way for wastewater treatment plants to solve the problem of nitrate removal 12.25 mg·g−1.

Aluminum-based metal-organic frameworks for adsorptive removal of anti-cancer (methotrexate) drug from aqueous solutions

N-Nitrosodipropylamine (NDPA) is a class of nitrogenous disinfection by-products (N-DBPs) with high toxicity. Although NDPA present in water bodies is at relatively low concentrations, the potential risk is high due to its high toxicity and bioaccumulation. Metal-organic frameworks (MOFs), a new type of porous material with remarkable functionality, have shown great performance in a wide variety of applications in adsorption. This is the first study investigating the adsorption of MOFs on NDPA. Herein, UiO-66 with -NH2 and imidazolium functional groups were synthesized by modifying UiO-66 after amination. Adsorption kinetics and isotherm models were used to compare the adsorption properties of the two materials for low-concentration NDPA in water. The results showed that the behavior of all the adsorbents was consistent with the Langmuir model and the pseudo-second-order model and that the adsorption was homogeneous chemisorption. The structures of the nanoparticles were characterized by FTIR, zeta potential, XRD, SEM and BET measurements. Based on the characteristics, four adsorption mechanisms, namely electron conjugation, coordination reaction, anion-π interaction, and van der Waals forces, were simultaneously involved in the adsorption. The influencing factor experiment revealed that the adsorption of UiO-66-NH2 and (I-)Meim-UiO-66 involved hydrogen bonding and electrostatic interactions, respectively.

Mechanistic insight into the adsorption of low concentrations of N-nitrosodiethylamine in water by functional MIL-96: Experiments and theoretical calculations