Bowknot-like Zr/La bimetallic organic frameworks for enhanced arsenate and phosphate removal: Combined experimental and DFT studies

Intertwined role of mechanism identification by DFT-XAFS and engineering considerations in the evolution of P adsorbents

Adsorption method exhibits promising potential in effectively removal of phosphate from wastewater, yet it faces tremendous challenges in practical application. Limited comprehension of adsorption mechanisms and the lack of evaluation method for scaling up application are the two main obstacles. To fully realize the practical application of P adsorbents, we reviewed advanced tools, including density functional theory (DFT) and/or X-ray absorption fine structure (XAFS) to elucidate mechanisms, underscored the significance of thermodynamics and kinetics in engineering design, and proposed strategies for regenerating and reusing P adsorbents. Specifically, we delved into the utilization of DFT and XAFS to gain insights into adsorption mechanisms, focusing on active site verification and molecular interaction configurations. Additionally, we explored precise calculation methods for adsorption thermodynamics and adsorption kinetics, encompassing thermodynamic equilibrium constants, reactor selection, and the regeneration, recovery, and disposal of P adsorbents. Our comprehensive review aims to serve as a guiding light in advancing the development of highly efficient P adsorbents for engineering applications.

Amino-functionalized cellulose composite for efficient simultaneous adsorption of tetracycline and copper ions: Performance, mechanism and DFT study

A novel cellulose composite (denoted as PEI@MMA-1) with porous interconnected structure was prepared by adsorbing methyl cellulose (MC) onto microcrystalline cellulose (MCC) and cross-linking polyethyleneimine (PEI) with MCC by the action of epichlorohydrin, which had the excellent adsorption property, wettability and elasticity. The performances of PEI@MMA-1 composite for removing tetracycline (TC), Cu2+ and coexistent pollutant (TC and Cu2+ mixture) were systematically explored. For single TC or Cu2+ contaminant, the maximum adsorption capacities were 75.53 and 562.23 mg/g at 30 °C, respectively, while in the dual contaminant system, they would form complexes and Cu2+ could play a "bridge" role to remarkably promote the adsorption of TC with the maximum adsorption capacities of 281.66 and 253.58 mg/g for TC and Cu2+. In addition, the adsorption kinetics, isotherms and adsorption mechanisms of single-pollutant and dual-pollutant systems have been thoroughly investigated. Theoretical calculations indicated that the amide group of TC molecule with the assistance of Cu2+ interacted with the hydroxyl group of PEI@MMA-1 composite to enhance the TC adsorption capacity. Cycle regeneration and fixed bed column experiments revealed that the PEI@MMA-1 possessed the excellent stability and utility. Current PEI@MMA-1 cellulose composite exhibited a promising application for remediation of heavy metals and antibiotics coexistence wastewater.

A bimetallic organic framework based fluorescent aptamer probe for the detection of zearalenone in cereals

In this work, a bimetallic organic framework (Cu/UiO-66) based "turn on" fluorescent aptamer probe was designed for the high-efficiency detection of zearalenone (ZEN). In the probe, the 6-carboxyfluorescein-labeled aptamer (FAM-Apt) was used as the recognition element, and the electrostatic interaction, coordination effect, and photoinduced electron transfer effect between FAM-Apt and Cu/UiO-66 caused fluorescence quenching. When ZEN existed, FAM-Apt recognized ZEN specifically, causing FAM-Apt to separate from the surface of Cu/UiO-66 and recovery of fluorescence. Under the optimal conditions, the probe had a linear detection range of 0.5 ng/mL-60 ng/mL, and the detection limit was 0.048 ng/mL. The application potential of the probe was verified by real detection of various cereals and their products, with a standard recovery from 83.67 %-106.8 %. The development of this efficient, rapid, and sensitive ZEN detection method provides a new platform for the quality control of cereals and their products.

Thermal Air Oxidation-Mediated Synchronous Coordination and Carbonation of Lanthanum on Biochar toward Phosphorus Adsorption from Wastewater

Biochar has attracted increasing attention as the sustainable and structure-tunable carrier for lanthanum (La) species for diverse applications. Carbonated La species possesses a higher biocompatibility and a lower leaching potential than other commonly used La species, while less attention is paid on the application of carbonated La in phosphorus (P) adsorption. Herein, thermal air oxidation (TAO) was applied as a novel strategy for synchronously tuning the coordination environment and chemical species of La on biochar surface. The results demonstrated that TAO induced the coordination of La with oxidation-generated oxygenated functional groups (OFGs) and carbonation of La species by the oxidation-generated CO2 on the biochar surface. The batch adsorption results showed that the Qm of resultant biochar remarkably increased from 68.92 to 132.49 mg/g at 1 g/L dosage. It also showed a robust adsorption stability in pH 2-6, a strong resistance to the co-existing Cl-, SO42-, NO3-, CO32-, or HCO3-, a stable adsorption recyclability, and an ultralow La leaching potential. The P adsorption was dominated by ligand exchange-induced inner-sphere complexation. In practical swine wastewater, the resultant biochar composite (1 g/L) removed 99.87% of P from 92.3 to 0.12 mg/L at a practical pH of 7.12. The density functional theory calculation further revealed the significant role of the binding of carbonated La by the biochar surface OFGs in reducing the P adsorption energies, indicating the synergism between the oxygenated biochar carrier and the carbonated La in P adsorption. Finally, this study provided a novel route to synchronously tune the coordination environment and chemical species of La on biochar via a facile TAO process for high-efficient P adsorption from wastewater.

Insights into the mechanism involved by electric double layer on phosphate removal of metal-bearing environmental remediation agent: Taking tricalcium aluminate as representative

Metal-bearing materials are known to be desirable environmental captures for phosphate removal, yet few studies focus on understanding the reaction process, especially formed a special phenomenon, i.e., electric double layer (EDL), which might influence the phosphate removal. To fill in this gap, we fabricated metal-bearing tricalcium aluminate (C₃A, Ca₃Al₂O₆) as representative, to remove phosphate and unveil the impact by electric double layer (EDL). Specifically, a preeminent removal capacity of 142.2 mg·g^-1 was achieved at the initial phosphate concentration below 300 mg·L^-1. Following thorough the characterizations, the process was that the released Ca²⁺ or Al³⁺ of C₃A formed positive charged stern layer attracted phosphate to generate Ca or Al-precipitation. At high phosphate concentration (>300 mg·L^-1), C₃A exhibited inferior removal capability for phosphate (<45 mg·g^-1), due to the aggregation of C₃A particles with low water permeability under the EDL effect, obstructing Ca²⁺ and Al³⁺ to release for phosphate removal. In addition, the feasibility application of C₃A was evaluated based on response surface methodology (RSM), highlighting its prospective phosphate treatment. This work not only provides a theoretical guidance for the application of C₃A to remove phosphate, but also deepens the understand of phosphate removal mechanism by metal-bearing materials, shedding light on environmental remediation.

Photo-Fenton self-cleaning carbon fibers membrane supported with Zr-MOF@Fe2O3 for effective phosphate removal from algae-rich water

Adsorbents featuring abundant binding sites and high affinity to phosphate have been used to resolve water eutrophication. However, most of the developed adsorbents were focused on improving the adsorption ability of phosphate but ignored the effect of biofouling on the adsorption process especially used in the eutrophic water body. Herein, a novel MOF-supported carbon fibers (CFs) membrane with high regeneration and antifouling capability, was prepared by in-situ synthesis of well-dispersed MOF on CFs membrane, to remove phosphate from algae-rich water. The hybrid UiO-66-(OH)₂@Fe₂O₃@CFs membrane exhibits a maximum adsorption capacity of 333.3 mg g^-1 (pH 7.0) and excellent selectivity for phosphate sorption over coexisting ions. Moreover, the Fe₂O₃ nanoparticles anchored on the surface of UiO-66-(OH)₂ through 'phenol-Fe(III)' reaction can endow the membrane with the robust photo-Fenton catalytic activity, which improves long-term reusability even under algae-rich condition. After 4 times photo-Fenton regenerations, the regeneration efficiency of the membrane could remain 92.2%, higher than that of hydraulic cleaning (52.6%). Moreover, the growth of C. pyrenoidosa was significantly reduced by 45.8% within 20 days via metabolism inhibition due to membrane-induced P-deficient conditions. Hence, the developed UiO-66-(OH)₂@Fe₂O₃@CFs membrane holds significant prospects for large-scale application in phosphate sequestration of eutrophic water bodies.

Self-supported trimetallic NiZnLa nanosheets on hierarchical porous graphene oxide-polymer composite fibers for enhanced phosphate removal from water

Phosphate-induced water eutrophication has attracted global attention. Fabricating adsorbents with both high phosphate adsorption affinity and accessible separation property is challenging. Herein, PG@NZL, a hierarchical nanocomposite fibrous membrane, was fabricated via in-situ growth of La-doped NiZn-LDH (NiZnLa_0.1) over electrospun graphene oxide-polymer composite fibers (PG). The porous surface of the PG fibers provided abundant anchor sites for the vertical self-supported growth of NiZnLa_0.1 nanosheets, contributing to a high surface area. The La-doped NiZnLa_0.1 trimetallic LDH achieved a much higher adsorption capacity than NiZn-LDH. The negative adsorption energy (-1.45 eV), calculated with DFT, confirmed its spontaneous adsorption potential for phosphate. Interestingly, the PG fibers contributed to oxygen vacancies and the metal center electronic structure evolution of NiZnLa_0.1, thus strengthening the coordination with phosphate. Mechanistic analysis revealed that the high adsorption capacity of PG@NZL is attributed to its superior anion exchange property, oxygen vacancies, and inner-sphere complexation. Therefore, the flexible and easily separated PG@NZL nanocomposite fibrous membrane is a promising adsorbent for effectively treating phosphate-bearing wastewater.

Defluoridation using hydroxyapatite implanted lanthanum organic framework-based bio-hybrid beads

The present study reports on biopolymer based material namely HAp–La-BTC MOFs@Alg–CS hybrid beads were developed and it was potentially employed for fluoride removal.