The Selective Removal of Bisphenol A Using a Magnetic Adsorbent Fused with Bisphenol A-Binding Peptides

The potential of bisphenol A (BPA)-binding peptides fused to magnetic beads is demonstrated as novel adsorbents that are reusable and highly selective for BPA removal from aqueous environments, in which various interfering substances coexist. Magnetic beads harboring peptides (peptide beads) showed a higher BPA removal capacity (8.6 mg/g) than that of bare beads without peptides (2.0 mg/g). The BPA adsorption capacity of peptide beads increased with the number of peptides fused onto the beads, where monomeric, dimeric, or trimeric repeats of a BPA-binding peptide were fused to magnetic beads. The BPA-adsorbing beads were regenerated using a methanol-acetic acid mixture, and after six regeneration cycles, the adsorption capacity remained above 87% of its initial capacity. The selective removal of BPA was confirmed in the presence of BPA analogs with high structural similarity (bisphenol F and bisphenol S) or in synthetic wastewater. The present work is a pioneering study that investigates the selective affinity of peptides to remove specific organics with high selectivity from complex environmental matrices.

Optimization of Electron Transport Pathway: A Novel Strategy to Solve the Photocorrosion of Ag-Based Photocatalysts

Although Ag-containing photocatalysts exhibit excellent photocatalytic ability, they present great challenges owing to their photocorrosion and ease of reduction. Herein, an electron acceptor platform of Ag2O/La(OH)3/polyacrylonitrile (PAN) fiber was constructed using a heterojunction strategy and electrospinning technology to develop a novel photocatalytic membrane with a redesigned electron transport pathway. Computational and experimental results demonstrate that the optimized electron transport pathway included intercrystal electron transfer induced by the La-O bond between Ag2O and La(OH)3 as well as electron transfer between the catalyst crystal and electrophilic PAN membrane interface. In addition, the photocatalytic performance of the Ag2O/La(OH)3 membrane for tetracycline (TC) removal was still above 97% after five photocatalytic reaction cycles. Furthermore, the carrier life was greatly extended. Mechanistic study revealed that photogenerated holes on the Ag2O/La(OH)3 membrane were the main reactive species in TC degradation. Overall, this study proposes a novel electron transport pathway strategy that effectively solves the problems of photocatalyst photocorrosion and structural instability.

Effective Removal of Cd from Aqueous Solutions Using P-Loaded Ca-Mn-Impregnated Biochar

Cadmium (Cd) pollution in wastewater has become an increasingly widespread concern worldwide. Studies on Cd (II) removal using phosphate-adsorbed sorbents are limited. This study aimed to elucidate the behaviors and mechanisms of Cd (II) sorption on phosphate-loaded Ca-Mn-impregnated biochar (Ps-CMBC). The Cd (II) sorption on Ps-CMBC reached equilibrium within 2 h and exhibited a higher sorption efficiency than biochar and CMBC. Additionally, the Langmuir isotherm could better describe the Cd (II) adsorption on the sorbents. P75-CMBC had a maximum Cd (II) sorption capability of 70.13 mg·g-1 when fitted by the Langmuir isotherm model, which was approximately 3.18 and 2.86 times greater than those of biochar and CMBC, respectively. Higher pH (5-7) had minimal effect on Cd (II) sorption capacity. The results of characterization analyses, such as SEM-EDS, FTIR, and XPS, suggested that there was a considerable difference in the sorption mechanisms of Cd (II) among the sorbents. The primary sorption mechanisms for biochar, CMBC, and Ps-CMBC included electrostatic attraction and surface complexation; additionally, for Ps-CMBC, Cd (II)-π interactions and coordination of Cd (II) with P=O were critical mechanisms for Cd (II) removal. The results of this study demonstrate that phosphate-loaded CMBC can be used as an effective treatment for heavy metal pollution in aqueous media.

Graphene-based materials for effective adsorption of organic and inorganic pollutants: A critical and comprehensive review

Water scarcity has been felt in many countries and will become a critical issue in the coming years. The release of toxic organic and inorganic contaminants from different anthropogenic activities, like mining, agriculture, industries, and domestic households, enters the natural waterbody and pollutes them. Keeping this in view in combating the environmental crises, removing pollutants from wastewater is one of the ongoing environmental challenges. Adsorption technology is an economical, fast, and efficient physicochemical method for removing both organic and inorganic pollutants, even at low concentrations. In the last decade, graphene and its composite materials have become the center of attraction for numerous applications, including wastewater treatment, due to the large surface area, highly active surface, and exclusive physicochemical properties, which make them potential adsorbents with unique physicochemical properties, like low density, chemical strength, structural variability, and the possibility of large-scale fabrications. This review article provides a thorough summary/critical appraisal of the published literature on graphene-, GO-, and rGO-based adsorbents for the removal of organic and inorganic pollutants from wastewater. The synthesis methods, experimental parameters, adsorption behaviors, isotherms, kinetics, thermodynamics, mechanisms, and the performance of the regeneration-desorption processes of these substances are scrutinized. Finally, the research challenges, limitations, and future research studies are also discussed. Certainly, this review article will benefit the research community by getting substantial information on suitable techniques for synthesizing such adsorbents and utilizing them in water treatment and designing water treatment systems.

Molecularly imprinted polymers for environmental adsorption applications

Molecular imprinting polymers (MIPs) are synthetic materials with pores or cavities to specifically retain a molecule of interest or analyte. Their synthesis consists of the generation of three-dimensional polymers with specific shapes, arrangements, orientations, and bonds to selectively retain a particular molecule called target. After target removal from the binding sites, it leaves empty cavities to be re-occupied by the analyte or a highly related compound. MIPs have been used in areas that require high selectivity (e.g., chromatographic methods, sensors, and contaminant removal). However, the most widely used application is their use as a highly selective extraction material because of its low cost, easy preparation, reversible adsorption and desorption, and thermal, mechanical, and chemical stability. Emerging pollutants are traces of substances recently found in wastewater, river waters, and drinking water samples that represent a special concern for human and ecological health. The low concentration in which these pollutants is found in the environment, and the complexity of their chemical structures makes the current wastewater treatment not efficient for complete degradation. Moreover, these substances are not yet regulated or controlled for their discharge into the environment. According to the literature, MIPs, as a highly selective adsorbent material, are a promising approach for the quantification and monitoring of emerging pollutants in complex matrices. Therefore, the main objective of this work was to give an overview of the actual state-of-art of applications of MIPs in the recovery and concentration of emerging pollutants.

Toward Selective Oxidation of Contaminants in Aqueous Systems

The presence of diverse pollutants in water has been threating human health and aquatic ecosystems on a global scale. For more than a century, chemical oxidation using strongly oxidizing species was one of the most effective technologies to destruct pollutants and to ensure a safe and clean water supply. However, the removal of increasing amount of pollutants with higher structural complexity, especially the emerging micropollutants with trace concentrations in the complicated water matrix, requires excessive dosage of oxidant and/or energy input, resulting in a low cost-effectiveness and possible secondary pollution. Consequently, it is of practical significance but scientifically challenging to achieve selective oxidation of pollutants of interest for water decontamination. Currently, there are a variety of examples concerning selective oxidation of pollutants in aqueous systems. However, a systematic understanding of the relationship between the origin of selectivity and its applicable water treatment scenarios, as well as the rational design of catalyst for selective catalytic oxidation, is still lacking. In this critical review, we summarize the state-of-the-art selective oxidation strategies in water decontamination and probe the origins of selectivity, that is, the selectivity resulting from the reactivity of either oxidants or target pollutants, the selectivity arising from the accessibility of pollutants to oxidants via adsorption and size exclusion, as well as the selectivity due to the interfacial electron transfer process and enzymatic oxidation. Finally, the challenges and perspectives are briefly outlined to stimulate future discussion and interest on selective oxidation for water decontamination, particularly toward application in real scenarios.

A molecularly imprinted polymer on chromium (ΙΙΙ) oxide nanoparticles for spectrofluorometric detection of bisphenol A

A unique fluorescent probe for the detection of bisphenol A (BPA) was established by creating a molecularly imprinted polymer (MIP) shell on chromium (ΙΙΙ) oxide nanoparticles (Cr₂O₃ NPs). The advantages of high selectivity of MIPs and the strong fluorescence property of Cr₂O₃ NPs were combined for the preparation of the probe. MIPs-coated Cr₂O₃ NPs were composed by anchoring MIP layer on the surface of Cr₂O₃ NPs using one-pot precipitation polymerization. Acrylic-based monomer and cross-linker were used to prepared MIP. The MIP-coated Cr₂O₃ NPs were characterized by spectrofluorometery, Fourier transform infrared spectroscopy, transmission electron microscopy, field transmission electron microscopy, dynamic light scattering, EDX and elemental mapping. The prepared NPs showed strong fluorescence emission at 360 nm excited at 300 nm which quenched in the presence of BPA. The dynamic range of the optical sensor was in the range of 0.04-4.4 μmol L^-1 and the detection limit was 0.015 μmol L^-1. The relative standard deviation was 2.2 and 1.3% for the concentration levels of 0.14 and 3.1 μmol L^-1, respectively. The probe had a great selectivity in the determination of BPA with an imprinting factor of 6.3. The sensor was applied for the quantification of bisphenol A in water samples.

A semi-covalent molecularly imprinted fluorescent sensor for highly specific recognition and optosensing of bisphenol A

A novel mesoporous fluorescent molecularly imprinted sensor for selective detection of bisphenol A (BPA) in food materials was fabricated via a semi-covalent imprinting method. The imprinting precursor that served as an alternative template molecule for BPA was prepared via thermally reversible isocyanate bonding, which effectively improved the imprinting efficiency for the molecularly imprinted sensor. Carbon dots (CDs) were embedded in mesoporous silica as signal recognition elements that exhibited quenching upon BPA binding. Subsequently, through the sol-gel process, the molecularly imprinted layer was coated on the CDs silica layer and provided specific recognition sites for BPA. The composite of CDs embedded in the mesoporous molecularly imprinted polymer (CDs@MIP) was characterized with scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, Brunauer-Emmett-Teller measurements and thermogravimetric analysis. The mechanism of carbon dots quenching and the high selectivity of CDs@MIP towards BPA were explored. The linear response range of the sensor was from 0.025 mg L^-1 to 2 mg L^-1 with a limit of detection of 0.016 mg L^-1. The method was successfully applied for the determination of food samples and recoveries ranged from 92.5% to 101.1%. The BPA contents in actual samples were determined using high performance liquid chromatography and the proposed sensor, showing no significant difference between the two methods.

Preparation of biochar by mango peel and its adsorption characteristics of Cd(ii) in solution

Biochars were prepared by pyrolyzing mango peel waste at 300, 400, 500, 600 and 700 °C. Various characterizations were carried out to explore the effect of pyrolysis temperature on the biochars. The data indicated that the physical and chemical properties of biochar such as pH, element ratio, specific surface area and functional groups changed with the increase of pyrolysis temperature. The yield and contents of hydrogen, nitrogen and oxygen decreased, while contents of the ash and carbon, pH and specific surface area of the biochars increased. In addition, the molar ratios of H/C, O/C and (O + N)/C decreased. In this study, batch adsorption experiments for Cd(ii) adsorption were performed with initial Cd(ii) concentrations of 10-300 mg L-1, contact times of 0-2880 min, various pH (2-8) and biochar dose (1-20 g L-1). Langmuir isotherm and pseudo-second-order kinetics models were better fits than other models, suggesting the dominant adsorption of mango peel biochars is via monolayer adsorption. Biochar derived at 500 °C was found to have the highest adsorption capacity of 13.28 mg g-1 among all biochars and the adsorption efficiency was still 67.7% of the initial adsorption capacity after desorption for 4 times. Based on adsorption kinetics and isotherm analysis in combination with EDS, FTIR and XRD analysis, it was concluded that cation exchange, complexation with surface functional groups and precipitation with minerals were the dominant mechanisms responsible for Cd adsorption by mango peel biochar. The study suggested that mango peel can be recycled to biochars and can be used as a low-cost adsorbent for Cd(ii) removal from wastewater.

Reasonable design and sifting of microporous carbon nanosphere-based surface molecularly imprinted polymer for selective removal of phenol from wastewater

Highly selective surface molecularly imprinted polymer (SMIP) was prepared on glucose-derived microporous carbon nanospheres (GMCNs) by surface molecular imprinting technology for the removal of phenol from wastewater. GMCNs with rich pore structure and surface oxygenic functional groups were adopted as support materials, on which the active layers were constructed by grafting silane coupling agent 3-(methacryloyloxy) propyltrimethoxysilane. Then with phenol as template molecule, different types and amounts of functional monomer (including methacrylic acid and 4-vinylpyridine (4-VP)) were screened for optimizing imprinting conditions suitable for phenol adsorption, and a series of SMIP was obtained through crosslinking polymerization. The adsorption behaviors of SMIP were evaluated by UV spectrophotometry. The results show that, when 4-VP is used as functional monomer, the resultant 4-VP/SMIP exhibites an excellent adsorption capacity of 85.72 mg g^-1. The relative selectivity factor for phenol against hydroquinone, p-nitrophenol and p-tert-butylphenol is 8.38, 7.96 and 6.67, respectively, indicating outstanding adsorption capacity and selectivity of 4-VP/SMIP. The pseudo-second-order model and Langmuir‒Freundlich model fit better than other models for the adsorption of phenol. 4-VP/SMIP is promising for selective removal and enrichment recovery towards phenol in wastewater.

Silver-based semiconductor Z-scheme photocatalytic systems for environmental purification

Silver-based semiconductor photocatalysts are promising materials for solving environmental and energy issues due to their strong optical absorption, excellent quantum efficiency and photoelectrochemical properties. However, the uncontrollable photocorrosion and high use cost of single silver-based semiconductor photocatalysts limit its practical application. The construction of Z-scheme photocatalytic systems that mimic natural photosynthesis can not only enhance the photocatalytic activity of silver-based semiconductor photocatalysts, but also improve their stability and reduce the use costs. This critical review concisely highlights the basic principles of Z-scheme photocatalytic systems, and discusses the construction of silver-based semiconductor Z-scheme photocatalytic systems and the roles of metallic Ag in there and summarizes the synthesis methods of silver-based semiconductor Z-scheme photocatalytic systems. Then, a series of the solar-driven applications are elaborated, including organic pollutants degradation, hydrogen production, and carbon dioxide reduction. Meanwhile, the mechanism and difficult level of these photocatalytic reactions are also described. Besides, metal organic frameworks (MOFs) as a novel type of photocatalysts have attracted growing attention. The novel combination of silver-based semiconductors with typical photoactive MOFs is highlighted based on the Z-scheme photocatalytic systems. Eventually, the future challenges and prospects in the development of silver-based semiconductor Z-scheme photocatalytic systems are presented.

Comparison of Four Adsorption Isotherm Models for Characterizing Molecular Recognition of Individual Phenolic Compounds in Porous Tailor-Made Molecularly Imprinted Polymer Films

A molecularly imprinted polymer (MIP) film using catechol as the template was designed for adsorption of a range of phenols from water. Four different isotherm models (Langmuir (LI), Freundlich (FI), Langmuir-Freundlich (L-FI), and Brunauer, Emmett, and Teller (BET)) were used to study the MIP adsorption of five phenolic compounds: phenol (Ph), 2-methylphenol (2-MP), 3-methylphenol (3-MP), 2-chlorophenol (2-CP), and 4-teroctylphenol (4-OP). Each model was evaluated for its fit with the experimental data, and key parameters, including a number of binding sites and binding site energies, were compared. Though the LI, L-FI, and BET models showed good agreement for estimation of the number of binding sites and affinity for most adsorbates, no single model was suitable for all. The LI and L-FI models gave the best fitting statistics for the Ph, 2-MP, 3-MP, and 2-CP. The recognition of 4-OP, which has much higher binding affinities than the smaller phenolic compounds not attributable to hydrophobicity alone, was explained only by the BET model, which indicates the formation of multilayers. The BET model failed only with phenol. MIPs also showed higher adsorption capacities and improved homogeneity over the analogous non-imprinted polymers.

Adsorption Characteristics and Mechanism of Bisphenol A by Magnetic Biochar

In this paper, biochar (BC) was prepared from discarded grapefruit peel and modified to prepare magnetic biochar (MBC). Physical and chemical properties of BC and MBC were characterized, and the results showed that the type of iron oxide loaded by MBC was γ-Fe₂O₃. Compared with BC, MBC has a larger specific surface area and pore volume, with more oxygen-containing functional groups on the surface. BC and MBC were used to adsorb and remove endocrine-disrupting chemical (EDC) bisphenol A (BPA) from simulated wastewater. The results showed that the adsorption kinetics and adsorption isotherm of BPA adsorption by BC and MBC were mainly in accordance with the pseudo-second-order kinetics model and the Langmuir model. This indicates that the adsorption of BPA on BC and MBC is mainly a chemically controlled monolayer adsorption. Adsorption thermodynamics show that BC and MBC adsorption of BPA is a spontaneous exothermic reaction, and lowering the temperature is conducive to the adsorption reaction. The effect of solution pH on the adsorption of BPA by both was significant. The optimum pH for BC and MBC to absorb BPA was 6 and 3, respectively. The concentration of Na⁺ in the range of 0–0.10 mol·L⁻¹ can promote the adsorption of BPA to MBC. MBC loaded with γ-Fe₂O₃ not only has excellent magnetic separation ability, but can also reach about 80% of the initial adsorption capacity after four cycles of adsorption. By analyzing the adsorption mechanism, it was found that the H-bond and the π–π electron donor–acceptor interaction (EDA) were the main forces for BC and MBC to adsorb BPA.

Fast, efficient and clean adsorption of bisphenol-A using renewable mesoporous silica nanoparticles from sugarcane waste ash

Even with all the biological problems associated with bisphenol-A (BPA), this chemical is still being widely used, especially in thermal paper receipts. In this study, renewable mesoporous silica nanoparticles (MSN), obtained from sugarcane ash, functionalized with hexadecyltrimethylammonium (CTAB) were applied as an adsorbent in the removal of BPA from the aqueous solution. The versatility of this material and its BPA adsorption capacity were tested at different pH values, being practically constant at pH between 4 and 9, with a slight increase in pH 10 and a greater increase in pH 11. The removal time evaluation indicates a very fast adsorption process, removing almost 90% of BPA in the first 20 min of contact. The kinetic model indicates a monolayer formation of BPA molecules on the MSN-CTAB surface. The maximum adsorption capacity (Q_max) was 155.78 mg g⁻¹, one of the highest found in literature, and the highest for material from a renewable source.

Utilization of renewable mesoporous silica nanoparticles, from sugarcane ash, as an adsorbent for removal of an endocrine disruptive compound, bisphenol-A.

A novel Fe3O4/graphene oxide/citrus peel-derived bio-char based nanocomposite with enhanced adsorption affinity and sensitivity of ciprofloxacin and sparfloxacin

To create more active adsorption sites on biochar, the Fe₃O₄/GO/citrus peel-derived magnetic bio-nanocomposite (mGOCP) with hierarchically porous architectures was synthesized by a facile one-pot hydrothermal approach for efficient removal of fluoroquinolone antibiotics ciprofloxacin (CIP) and sparfloxacin (SPA). The characterization analysis of bio-nanocomposites showed that the incorporation of GO could ensure relatively higher surface area (1556 cm² g^-1), more abundant pore structure, and higher thermal stability within mGOCP bio-nanocomposites than Fe₃O₄/citrus peel-derived magnetic bio-nanocomposites (mCP). And the mGOCP-1% attained outstanding adsorption capacity for CIP (283.44 mg g^-1) and SPA (502.37 mg g^-1), respectively. The primary adsorption mechanisms for CIP and SPA included π-π electron donor-acceptor interaction, H-bonding, hydrophobic interaction and electrostatic interaction. Overall, the surface morphology and structural composition of biochars could be regulated with GO to facilitate the adsorption capacity. Moreover, the developed mGOCP could be extended as a potential adsorbent for removal of other emerging organic pollutants in water.

Decontamination of lead and tetracycline from aqueous solution by a promising carbonaceous nanocomposite: Interaction and mechanisms insight

Innovative carbonaceous nano-chlorapatites (CNClAPs) which originated from the pyrolyzation of the mixture of bamboo residues and chlorapatites varying from 400 °C to 600 °C were used to investigate the decontamination efficacy of lead (Pb²⁺) and tetracycline (TC) from wastewater. Rising pyrolytic temperature can highly improve the decontamination efficacy, of which CNClAP600 exhibited the most remarkable effects for Pb²⁺ and TC decontamination (90.37% for Pb²⁺ and 86.58% for TC at pH = 7). The kinetic, isotherm and characterization analysis demonstrated that the inner mechanisms for the decontamination of Pb²⁺ and TC involved precipitation, electrostatic interaction, hydrogen bonding, π-π interaction and pore filling. Experiment indicated that the enhancement and competitive adsorption resulted from the interaction between Pb²⁺ and TC could facilitate their joint decontamination under low concentrations. This research shed light on the management of coexisting heavy metals and organic matters contamination in wastewater by CNClAPs under different temperatures.

Insights into the effect of chemical treatment on the physicochemical characteristics and adsorption behavior of pig manure-derived biochars

Chemical treatment could improve the adsorption performance of biochars (BC). In order to deal with Pb(II) pollution, four types of biochars including unmodified, acid-treated, alkali-treated, and magnetic-treated pig manure-derived biochars (PBCs) were prepared. The effect of chemical treatment on the physical property, chemical composition, and the adsorption behavior of biochars was compared. Magnetic and alkali treatment improved pore volume and specific surface areas, and the adsorption capacity and rates were enhanced. In contrast, the adsorption capacity of acid-treated BC decreased due to the significant decrease of ash content. The magnetic samples displayed the satisfactory absorption performance, which could achieve 99.8% removal efficiency within 15 min at a Pb(II) concentration of 50 mg/L. Considering its properties of excellent adsorption performance, fast reaction rate, and convenient recovery by an external magnetic field, magnetic biochar based on pig manure may provide an effective way to remove heavy metals and decrease the pig manure solid waste.

Water clusters contributed to molecular interactions of ionizable organic pollutants with aromatized biochar via π-PAHB: Sorption experiments and DFT calculations

Molecular interactions between biochars and ionizable organic pollutants (IOPs) are of great concern in natural environments, however the role of water clusters on the biochar surface remain unclear. The pH-dependent adsorption of aniline, phenol, 2-chlorophenol, 3-chlorophenol, 4-chlorophenol, 4-methylphenol and 4-nitrophenol onto bamboo wood derived biochar (BW700) as a model was conducted to identify conventional and novel interaction mechanisms between aromatized surface and IOPs. The dissociation constant (pK_a,surface) of surface functional groups of BW700 was characterized by acid-base titration and Zeta potential measurements. The pH-dependent adsorption behavior depended on the pK_a,IOP of IOPs and also related to the pK_a,surface of biochar surface. An obvious peak of adsorption coefficients (K_d) in the range of solution pH was shaped at pH_peak = (pK_a,IOP + pK_a,surface)/2, which cannot be well explained by the conventional mechanisms such as hydrophobic effects, π-π interaction, electrostatic attractions, and hydrogen-binding. The contribution of ice-like adlayer (water clusters) on aromatic surface as H-acceptors is proposed for the first time to the adsorption peak of IOP as H-donors at pH_peak. Density functional theory (DFT) calculations provided a possible structure of the complex combined with ice-like adlayer and aromatic substrate of BW700, and indicated that the adsorbing peak resulted from the multiple π-bond and polarization assisted H-bond (π-PAHB) interactions. Three distinct properties of π-PAHB were given, based on multiple π-bond, hydrophobicity-dependence and pH sensitivity. This novel mechanism extends the definition of H-bonds for better understanding the molecular interactions of IOP with carbonaceous materials and their environmental fate.

Investigating the adsorption behavior and the relative distribution of Cd2+ sorption mechanisms on biochars by different feedstock

The objective of this study was to investigate the adsorption behavior and the relative distribution of Cd²⁺ sorption mechanisms on biochars by different feedstock. Bamboo biochars (BBCs), corn straw biochars (CBCs) and pig manure biochars (PBCs) were prepared at 300-700 °C. Adsorption results showed PBCs have the best adsorption capacity for Cd²⁺, the extra adsorption capacity of PBCs mainly attributed to the precipitation or cation exchange, which played an important role in the removal of Cd²⁺ by PBCs. The contribution of involved Cd²⁺ removal mechanism varied with feedstock due to the different components and oxygen-containing functional groups. Cd²⁺-π interaction was the predominant mechanism for Cd²⁺ removal on biochars and the contribution proportion significantly decreased from 82.17% to 61.83% as the ash content increased from 9.40% to 58.08%. Results from this study may suggest that the application of PBC is a feasible strategy for removing metal contaminants from aqueous solutions.

Recent Progress of Imprinted Nanomaterials in Analytical Chemistry

Molecularly imprinted polymers (MIPs) are a type of tailor-made materials that have ability to selectively recognize the target compound/s. MIPs have gained significant research interest in solid-phase extraction, catalysis, and sensor applications due to their unique properties such as low cost, robustness, and high selectivity. In addition, MIPs can be prepared as composite nanomaterials using nanoparticles, multiwalled carbon nanotubes (MWCNTs), nanorods, quantum dots (QDs), graphene, and clays. This review paper aims to demonstrate and highlight the recent progress of the applications of imprinted nanocomposite materials in analytical chemistry.

Preparation of water-compatible molecularly imprinted thiol-functionalized activated titanium dioxide: Selective adsorption and efficient photodegradation of 2, 4-dinitrophenol in aqueous solution

A novel water-compatible surface molecularly imprinted thiol-functionalized titanium dioxide (TiO₂) material (CMIP-coated TiO₂) was prepared in water, using 2, 4-dinitrophenol (2, 4-DNP) as template molecule and o-phenylenediamine (OPDA) as both functional monomer and cross-linker. The as-synthesized materials were characterized by FESEM, FTIR, XRD, BET and UV-vis DRS. Moreover, we have investigated the adsorption capacity, adsorption selectivity and photodegradation activity of the CMIP-coated TiO₂ and non-molecular imprinted materials (CNIP-coated TiO₂). Additionally, the effects of pH and concentration of 2, 4-DNP on the degradation rate of 2, 4-DNP were also investigated. Results showed that CMIP-coated TiO₂ exhibited higher adsorption capacity, greater selectivity and faster photodegradation activity for 2, 4-DNP compared with the CNIP-coated TiO₂. Meanwhile, the specific selectivity to 2, 4-DNP over its structural analogue 4-nitrophenol (4-NP) and the enhanced photodegradation capacity were mainly attributed to the imprinted cavities on the surface of CMIP-coated TiO₂. Taking advantage of efficient removal capacity, high reusability and no-additional chemicals in imprinted process, the prepared materials can be potentially applied to "green" removal of 2, 4-DNP in wastewater.

Sorptive removal of ionizable antibiotic sulfamethazine from aqueous solution by graphene oxide-coated biochar nanocomposites: Influencing factors and mechanism

Significant concerns have been raised over antibiotics pollution in aquatic environments in recent years. In this study, sorption of sulfamethazine (SMT) by novel graphene oxide-coated biochar nanocomposites (GO-BC) based on graphene oxide (GO) with bamboo sawdust biochar (BC) was investigated. In comparison with the original BC, the sorption capacity of GO-BC for SMT increased by 1.14 times. Sorption of SMT onto GO-BC was proved to be dominantly by chemisorption, and Freundlich isotherm described the sorption adequately. It was found that variation of pH and ionic strength obviously affected the sorption of SMT, and GO-BC had a good sorption effect on SMT at pH 3.0-6.0 and lower ionic strength. Obvious enhancement (by 30%) in sorption of SMT on GO-BC was observed, which might be attributed to the increase of functional groups on the surface of GO-BC. Moreover, the main sorption mechanism for SMT was π-π electron-donor-acceptor interaction, while auxiliary sorption mechanisms were inferred as pore-filling, cation exchange, hydrogen bonding interaction and electrostatic interaction. The results indicated that GO-BC sorption was an efficient way for the removal of SMT.

Stabilized Nanoscale Zerovalent Iron Mediated Cadmium Accumulation and Oxidative Damage of Boehmeria nivea (L.) Gaudich Cultivated in Cadmium Contaminated Sediments

Nanoparticles can be absorbed by plants, but their impacts on phytoremediation are not yet well understood. This study was carried out to determine the impacts of starch stabilized nanoscale zerovalent iron (S-nZVI) on the cadmium (Cd) accumulation and the oxidative stress in Boehmeria nivea (L.) Gaudich (ramie). Plants were cultivated in Cd-contaminated sediments amended with S-nZVI at 100, 500, and 1000 mg/kg, respectively. Results showed that S-nZVI promoted Cd accumulation in ramie seedlings. The subcellular distribution result showed that Cd content in cell wall of plants reduced, and its concentration in cell organelle and soluble fractions increased at S-nZVI treatments, indicating the promotion of Cd entering plant cells by S-nZVI. In addition, the 100 mg/kg S-nZVI alleviated the oxidative damage to ramie under Cd-stress, while 500 and 1000 mg/kg S-nZVI inhibited plant growth and aggravated the oxidative damage to plants. These findings demonstrate that nanoparticles at low concentration can improve the efficiency of phytoremediation. This study herein develops a promising novel technique by the combined use of nanotechnology and phytoremediation in the remediation of heavy metal contaminated sites.

Construction of stable core–shell imprinted Ag-(poly-o-phenylenediamine)/CoFe2O4 photocatalyst endowed with the specific recognition capability for selective photodegradation of ciprofloxacin

The stable core–shell imprinted Ag-POPD/CoFe₂O₄ photocatalyst not only possessed high photocatalytic activity, but also exhibited the superior specific recognition capability for selective photodegradation of CIP.

A graphene oxide surface–molecularly imprinted polymer as a dispersive solid-phase extraction adsorbent for the determination of cefadroxil in water samples

Graphene oxide–functionalized molecularly imprinted polymer particles have been prepared for specific selective extraction and determination of cefadroxil in environmental water samples.

PES magnetic microspheres: preparation and performance for the removal of endocrine disruptor-BPA

PES magnetic microspheres were prepared via electrospraying and in situ reaction, and they were applied for the removal of BPA.