4-nitrophenol surface molecularly imprinted polymers based on multiwalled carbon nanotubes for the elimination of paraoxon pollution

A MOFs/MIPs@GAs Ternary Composite Catalytic System with Graphene Oxide Aerogels as the Multifunctional Skeleton for High-Efficiency Detoxification of Organophosphate Nerve Agents in Pure Water

Organophosphate nerve agents (OPs) are widely used as pesticides and chemical agents and pose a threat to human health and life. At present, most personal protective equipment usually only serves as physical protection and does not have an effect of chemical detoxification. In this work, ultra lightweight graphene oxide aerogels (GAs) have been used as a multifunctional skeleton to integrate the metal-organic frameworks (MOFs) and molecularly imprinted polymers (MIPs) together for obtaining a high-performance hybrid material (MOFs/MIPs@GAs) on hydrolysis detoxification of OPs. As a porous three-dimensional material full of carboxyl groups, GAs can not only support excellent mass transfer performance but also provide a proper pH self-buffering catalytic reaction external environment for hydrolyzing OPs. The obtained MOFs/MIPs@GAs can catalyze dimethyl-4-nitrophenyl phosphate (DMNP) hydrolysis detoxification rapidly in pure water (kobs = 0.2227 min-1, t1/2 = 3.11 min). This ternary hybrid material with exceptional performance and practical applicability has vast application prospects for the development of protective equipment.

Advances in molecularly imprinted materials for selective adsorption of phenolic pollutants from the water environment: Synthesis, applications, and improvement

The application of molecularly imprinted material (MIM) is widely employed as a material for removing phenolic pollutants from the water environment, owing to its exceptional capacity for selective adsorption and high sensitivity. In this paper, the preparation principle, bonding types, and preparation methods of MIM have been comprehensively introduced. Meanwhile, according to the binding type of MIM with phenolic pollutants, three categories of hydroxyl bonding, hydroxyl carboxyl bonding, and hydroxyl nitro bonding were carried out to explain its application to phenolic pollutants. Strategies for addressing the challenges of selective instability, high regeneration costs, and template leakage in MIM applications were summarized. These strategies encompassed the introduction of superior carriers, enhancements in preparation processes, and the utilization of molecular dynamics simulation-assisted technology. Finally, the prospects in the three aspects of material preparation, process coupling, and recycling. In summary, this paper has demonstrated the potential of utilizing MIM for the selective treatment of phenolic pollutants from the water environment.

Reduction and Degradation of Paraoxon in Water Using Zero-Valent Iron Nanoparticles

Paraoxon is an emerging organophosphate pollutant that is commonly used as a pesticide and a drug, hence increasing the risk of contamination of water supplies. Its intensive use for vector control has led to pollutions in soil and water. Paraoxon is very toxic, with an LD50 of 2 to 30 mg/kg in rats. It can be metabolized in the body from parathion; thus, exposure can lead to serious health effects. In this study, zero valent iron (Fe°/ZVI NPs) nanoparticles were synthesized and investigated for the degradation of Paraoxon, a chemical warfare agent and insecticide, in an aqueous solution. The effects of solution pH, initial pollutant concentration, ZVI NPs dosage and contact time on mineralization efficiency were examined. Batch experiments demonstrated that 15 mg L−1 of Paraoxon was mineralized at degradation efficiencies of 75.9%, 63.9% and 48.9% after three-hour treatment with 6.0, 4.0 and 2.0% w/v Fe°, respectively. The calculated kinetic rate constant kobs was 0.4791 h−1, 0.4519 h−1 and 0.4175 h−1 after treating 10, 15 and 20 mg L−1 of Paraoxon solution with 6.0% w/v Fe, respectively. The degradation dynamics were described by the first-order kinetic law as evidenced by rate constants independent of the initial Paraoxon concentration. The degradation efficiency was strongly dependent on pH, increasing with a decrease in pH, with maximum removal at pH 4. p-nitrophenol was detected as a degradation product, suggesting cleavage of the O-P bond and hydrolysis as possible reaction processes. This study showed that Fe° particles have the potential for degrading Paraoxon.

Mechanical Bond Approach to Introducing Self-Adaptive Active Sites in Covalent Organic Frameworks for Zinc-Catalyzed Organophosphorus Degradation

Mechanically interlocked molecules (MIMs) with discrete molecular components linked through a mechanical bond in space can be harnessed for the operation of molecular switches and machines, which shows huge potential to imitate the dynamic response of natural enzymes. In this work, rotaxane compounds were adopted as building monomers for the synthesis of a crown-ether ring mechanically intercalated covalence organic framework (COF). This incorporation of MIMs into open architecture implemented large amplitude motions, whose wheel slid along the axle in response to external stimulation. After impregnation with Zn²⁺ ions, the relative locations of two zinc active sites (crown-ether coordinated Zn(II) and bipyridine coordinated Zn(II)) are endowed with great flexibility to fit the conformational transformation of an organophosphorus agent during the hydrolytic process. Notably, the resulting self-adaptive binuclear zinc center in a crown-ether-threaded COF network is endowed with a record catalytic ability, with a rate over 85.5 μM min^-1 for organophosphorus degradation. The strategy of synthesis for porous artificial enzymes through the introduction of mechanically bound crown ether will enable significant breakthroughs and new synthetic concepts for the development of advanced biomimetic catalysts.

Targeted degradation of refractory organic compounds in wastewaters based on molecular imprinting catalysts

Efficient removal of low-concentration refractory pollutants is a crucial problem to ensuring water safety. The use of heterogeneous catalysis of molecular imprinting technology combined with traditional catalysts is a promising method to improve removal efficiency. Presently, the research into molecular imprinting targeting catalysts focuses mainly on material preparation and performance optimization. However, more researchers are investigating other applications of imprinting materials. This review provides recent progress in photocatalyst preparation, electrocatalyst, and Fenton-like catalysts synthesized by molecular imprinting. The principle and control points of target catalysts prepared by precipitation polymerization (PP) and surface molecular imprinting (S-MIP) are introduced. Also, the application of imprinted catalysts in targeted degradation of drugs, pesticides, environmental hormones, and other refractory pollutants is summarized. In addition, the reusability and stability of imprinted catalyst in water treatment are discussed, and the possible ecotoxicity risk is analyzed. Finally, we appraised the prospects, challenges, and opportunities of imprinted catalysts in the advanced oxidation process. This paper provides a reference for the targeted degradation of refractory pollutants and the preparation of targeted catalysts.

Ag(I) Pyridine-Amidoxime Complex as the Catalysis Activity Domain for the Rapid Hydrolysis of Organothiophosphate-Based Nerve Agents: Mechanistic Evaluation and Application

Two novel Ag(I) complexes containing synergistic pyridine and amidoxime ligands (Ag-DPAAO and Ag-PAAO) were first designed as complex monomers. Taking advantage of the molecular imprinting technique and solvothermal method, molecular imprinted porous cross-linked polymers (MIPCPs) were developed as a robust platform for the first time to incorporate Ag-PAAO into a polymer material as a recyclable catalyst. Advantageously, the observed pseudo first-order rate constant (k_obs) of MIPCP-Ag-PAAO-20% for ethyl-parathion (EP) hydrolysis is about 1.2 × 10⁴-fold higher than that of self-hydrolysis (30 °C, pH = 9). Furthermore, the reaction mechanism of the MIPCP-containing Ag-PAAO-catalyzed organothiophosphate was analyzed in detail using density functional theory and experimental spectra, indicating that the amidoxime can display dual roles for both the key coordination with the silver ion and nucleophilic attack to weaken the P-OAr bond in the catalytic active site.

Carbon Nanotubes (CNTs): A Potential Nanomaterial for Water Purification

Nanomaterials such as carbon nanotubes (CNTs) have been used as an excellent material for catalysis, separation, adsorption and disinfection processes. CNTs have grabbed the attention of the scientific community and they have the potential to adsorb most of the organic compounds from water. Unlike, reverse osmosis (RO), nanofiltration (NF) and ultrafiltration (UF) membranes aligned CNT membranes can act as high-flow desalination membranes. CNTs provide a relatively safer electrode solution for biosensors. The article is of the utmost importance for the scientists and technologists working in water purification technologies to eliminate the water crisis in the future. This review summarizes about the application of CNTs in water purification.

Simultaneous capture of methyl orange and chromium(vi) from complex wastewater using polyethylenimine cation decorated magnetic carbon nanotubes as a recyclable adsorbent

Most recently, the continuous deterioration of the aquatic environment triggered by both heavy metals and synthetic organic dyes has imparted serious threats to the ecosphere and drinking water safety. However, it is still extremely challenging to treat complex wastewater containing these two classes of pollutants via a one-step method owing to the significant differences in their physicochemical properties. In the current work, versatile magnetic MWCNTs decorated with PEI (denoted as MWCNTs@Fe3O4/PEI) was fabricated by a facile, rapid and reproducible strategy and applied to as a robust adsorbent for simultaneously removing methyl orange (MO) and Cr(vi) from aqueous solutions. The physicochemical properties of the as-designed nanohybrid were investigated using various analytical techniques, i.e. XRD, FT-IR, SEM, TEM, VSM, zeta potential, etc. It was found that the surface charge properties of the MWCNTs as well as its dispersion in aqueous solution were greatly changed after the introduction of PEI molecules. The resulting nanohybrid exhibited attractive adsorption capabilities toward anionic MO and Cr(vi). In the perspective of a mono-pollutant system, the time-dependent adsorption process matched well with a pseudo-second-order kinetics equation, the adsorption isotherm data at r.t. were well fitted by a Langmuir model with maximum monolayer uptake capacity of 1727.6 mg g-1 for MO and 98.8 mg g-1 for Cr(vi), and the removal process of both pollutants was thermodynamically spontaneous and exothermic. In the MO-Cr(vi) binary system, the uptake of Cr(vi) by the as-prepared adsorbent was evidently enhanced by the presence of MO, while the coexisting Cr(vi) exerted a small negative effect on the sorption of MO; which was attributed to the different adsorption mechanisms of both pollutants on the as-recommend adsorbent. The much better adsorbing performance of the resulting MWCNTs@Fe3O4/PEI for MO and Cr(vi) than that of the pristine MWCNTs or the MWCNTs/Fe3O4 composite was mainly ascribed to the high surface area of the MWCNTs, the high density of protonated N-rich groups of PEI as well as the excellent dispersion and solubility of the resulting nanocomposites. Moreover, the obtained nanohybrids can be easily recovered after being used by a permanent magnet and still retained high stability and excellent reusability after consecutive adsorption-desorption cycles, implying its great potential in practical applications. Therefore, the as-fabricated MWCNTs@Fe3O4/PEI composite could be recommended as a promising candidate adsorbent for the simultaneous capture of MO and Cr(vi) from complex wastewater via multiple uptake mechanisms (e.g. electrostatic attraction, π-π stacking and hydrogen bonding).

Catalytic degradation of organophosphorous nerve agent simulants by polymer beads@graphene oxide with organophosphorus hydrolase-like activity based on rational design of functional bimetallic nuclear ligand

The degradation of organophosphorous nerve agents is of primary concern due to the severe toxicity of these agents. Based on the active center of organophosphorus hydrolase (OPH), a bimetallic nuclear ligand, (5-vinyl-1,3-phenylene)bis(di(1H-imidazol-2-yl) methanol) (VPIM), was designed and synthesized, which contains four imidazole groups to mimic the four histidines at OPH active center. By grafting VPIM on graphene oxide (GO) surface via polymerization, the VPIM-polymer beads@GO was produced. The obtained OPH mimics has an impressive activity in dephosphorylation reactions (turnover frequency (TOF) towards paraoxon: 2.3 s^-1). The synergistic catalytic effect of the bimetallic Zn²⁺ nuclear center and carboxyl groups on surface of GO possibly contributes to the high hydrolysis on organophosphate substrate. Thus, a biomimetic catalyst for efficient degradation of some organophosphorous nerve agent simulants, such as paraoxon and chlorpyrifos, was prepared by constructing catalytic active sites. The proposed mechanism and general synthetic strategy open new avenues for the engineering of functional GOs for biomimetic catalysts.

Molecularly Imprinted Porous Aromatic Frameworks Serving as Porous Artificial Enzymes

Artificially designed enzymes are in demand as ideal catalysts for industrial production but their dense structure conceals most of their functional fragments, thus detracting from performance. Here, molecularly imprinted porous aromatic frameworks (MIPAFs) which are exploited to incorporate full host-guest interactions of porous materials within the artificial enzymes are presented. By decorating a porous skeleton with molecularly imprinted complexes, it is demonstrated that MIPAFs are porous artificial enzymes possessing excellent kinetics for guest molecules. In addition, due to the abundance of accessible sites, MIPAFs can perform a wide range of sequential processes such as substrate hydrolysis and product transport. Through its two functional sites in tandem, the MIPAF subsequently manifests both hydrolysis and transport behaviors. Advantageously, the obtained catalytic rate is ≈58 times higher than that of all other conventional artificial enzymes and even surpasses by 14 times the rate for natural organophosphorus hydrolase (Flavobacterium sp. strain ATCC 27551).

Recent advances in nanomaterials for water protection and monitoring

Nanomaterials (NMs) for adsorption, catalysis, separation, and disinfection are scrutinized. NMs-based sensor technologies and environmental transformations of NMs are highlighted.

Synthesis, characterization and application of core–shell magnetic molecularly imprinted polymers for selective recognition of clozapine from human serum

In this article, a magnetic molecularly imprinted polymer (MMIPs) based on Fe₃O₄@SiO₂ has been synthesized for simply extraction of clozapine (CLZ) from human serum.

Electrochemical sensor for chloramphenicol based on novel multiwalled carbon nanotubes@molecularly imprinted polymer

Herein, we present a novel electrochemical sensor for the determination of chloramphenicol (CAP), which is based on multiwalled carbon nanotubes@molecularly imprinted polymer (MWCNTs@MIP), mesoporous carbon (CKM-3) and three-dimensional porous graphene (P-r-GO). Firstly, 3-hexadecyl-1-vinylimidazolium chloride (C16VimCl) was synthetized by using 1-vinylimidazole and 1-chlorohexadecane as precursors. Then, C16VImCl was used to improve the dispersion of MWCNT and as monomer to prepare MIP on MWCNT surface to obtain MWCNTs@MIP. After that, the obtained MWCNTs@MIP was coated on the CKM-3 and P-r-GO modified glassy carbon electrode to construct an electrochemical sensor for the determination of CAP. The parameters concerning this assay strategy were carefully considered. Under the optimal conditions, the electrochemical sensor offered an excellent response for CAP. The linear response ranges were 5.0 × 10(-9)-5 × 10(-7)mol L(-1) and 5.0 × 10(-7)-4.0 × 10(-6), respectively, and the detection limit was 1.0 × 10(-10)mol L(-1). The electrochemical sensor was applied to determine CAP in real samples with satisfactory results.

An ion-imprinted functionalized SBA-15 adsorbent synthesized by surface imprinting technique via reversible addition-fragmentation chain transfer polymerization for selective removal of Ce(III) from aqueous solution

A novel Ce(III) ion-imprinted polymer (Ce(III)-IIP) has been prepared by surface imprinting technique with reversible addition-fragmentation chain transfer (RAFT) polymerization based on support matrix of SBA-15. The prepared adsorbent is characterized by FT-IR, XRD, SEM, TEM, nitrogen adsorption-desorption, GPC, and TGA. The results suggest that the surface imprinted polymer synthesized by RAFT is a thin layer. For adsorption experiments, Ce(III)-IIP is investigated to remove Ce(III) by column study at different flow rates, initial metal ion concentrations, and adsorption temperature. The dynamic kinetics analyses reveal that the overall adsorption process is successfully fitted with the pseudo-first-order kinetic model and the equilibrium time was 60 min. Meanwhile, the experimental data is in good agreement with Thomas model. Ce(III)-IIP has the excellent selectivity and regenerate property. Meanwhile, the proposed method has been successfully applied in the removal of Ce(III) in natural water samples with satisfactory results. All the results suggest that Ce(III)-IIP could be used as an excellent adsorbent for efficient removal of Ce(III) from aqueous solution.