Zhonghong Li

One-pot synthesis of multifunctional magnetic ferrite–MoS2–carbon dot nanohybrid adsorbent for efficient Pb(II) removal

Herein, we demonstrate a one-pot solvothermal synthetic method for fabricating MFe2O4 (M = Mn, Co)–MoS2–carbon dot (CD) nanohybrid composites (MnFMC, CoFMC) with excellent Pb(II) removal ability. Detailed characterization through SEM, XRD, UV-vis spectra, fluorescence spectra and VSM confirmed the formation of the nanohybrid composites. The adsorption behavior of the as-prepared nanohybrids was systematically studied using kinetic and equilibrium experiments, and the adsorption mechanism was further revealed using XPS and FTIR. Taking advantage of the cation substitution of abundant functional groups on the surface of CDs and MFe2O4 nanoparticles, as well as the large surface of available MoS2 for enhancing the sequestration of target metal-pollutants, the as-prepared composites exhibit high adsorption performances (588.24 mg g−1 for MnFMC and 660.67 mg g−1 for CoFMC) and show preferential Pb(II) sorption behavior with a high level concentration of competing cations (Ca(II)/Mg(II)). Moreover, these nanohybrid adsorbents exhibit excellent reusability, lower the effluent Pb(II) contents down to the ppb level, which satisfies the drinking water standard recommended by the World Health Organization, and are promising candidates for water purification.

Purification and identification of five novel antioxidant peptides from goat milk casein hydrolysates.

The present research described the preparation, purification, and identification of antioxidant peptides from goat milk casein (GMC). Goat milk casein was hydrolyzed by using a combination of neutral and alkaline proteases to obtain goat milk casein hydrolysates (GMCH) with high antioxidant activity. After desalting by nonpolar macroporous absorption resin, GMCH was isolated and purified by gel filtration chromatography and reversed-phase HPLC, respectively, and further identified by nanoliter electrospray ionization-tandem mass spectrometry. Antioxidant activities of GMC, GMCH, and pure peptides were evaluated and compared using free radical scavenging activity, metal ion chelating ability, and anti-lipid peroxidation ability. Compared with GMC, the free radical-scavenging ability and ferrous ion-chelating ability of GMCH increased significantly. The inhibition effect of lipid peroxidation of GMCH was much stronger than that of tert-butylhydroquinone and phytogermine and a little lower than that of ascorbic acid. The antioxidant activity of GMCH could be attributed to the high antioxidant activity of oligopeptides, especially 5 novel oligopeptides: Val-Tyr-Pro-Phe, Phe-Gly-Gly-Met-Ala-His, Phe-Pro-Tyr-Cys-Ala-Pro, Tyr-Val-Pro-Glu-Pro-Phe, and Tyr-Pro-Pro-Tyr-Glu-Thr-Tyr, which were first observed in GMCH. The antioxidant activity of these 5 novel oligopeptides and GMCH increased 3.59 to 380 times compared with GMC, combining anti-lipid peroxidation ability of GMCH, which indicated that GMCH and its purified fractions in different stages could be used as functional food ingredients, food additives, and pharmaceutical agents in the future.

Affinity adsorption of lysozyme with Reactive Red 120-modified magnetic chitosan microspheres.

Reactive Red 120 was utilized as an affinity dye-ligand to modify the surface of magnetic chitosan microspheres to improve the adsorption capacity for lysozyme. The impact of pH, ionic strength, adsorption time and initial lysozyme concentration on the adsorption of lysozyme from aqueous solutions was investigated. An increased adsorption amount of 116.9 mg/g lysozyme on Reactive Red 120 modified microspheres was achieved in comparison to 24.6 mg/g on unmodified magnetic chitosan microspheres. The adsorption behaviour of lysozyme by the Reactive Red 120 modified magnetic chitosan microspheres fitted the pseudo second-order kinetic and the Langmuir thermodynamic model. The desorption ratio was 92.6% using 1M NaCl phosphate buffer (pH 6.0) as the desorption agent. The adsorption capacity of the Reactive Red 120 modified magnetic chitosan microspheres did not decrease significantly after four adsorption-desorption cycles (P>0.05). The as-prepared Reactive Red 120 modified magnetic chitosan microspheres were then used for the extraction of lysozyme from egg white solutions. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) results showed that the purity of the obtained lysozyme was ~80.7% and that the recovery yield was ~89.1%.

Nutrient transformation during aerobic composting of pig manure with biochar prepared at different temperatures

The effects of the corn stalk charred biomass (CB) prepared at different pyrolysis temperatures as additives on nutrient transformation during aerobic composting of pig manure were investigated. The results showed that the addition of CB carbonized at different temperatures to pig manure compost significantly influenced the compost temperature, moisture, pH, electrical conductivity, organic matter degradation, total nitrogen, and NH3 variations during composting. Compared with control and adding CB charred at lower temperature treatments, the addition of CB prepared over 700°C resulted in higher pH (over 9.2) and NH3 emission and lower potherb mustard seed germination index value during the thermophilic phase. Peak temperatures of composts appeared at 7 days for control and 11 days for CB added treatments. During 90 days composting, the organic matter degradation could be increased over 14.8–29.6% after adding of CB in the compost mixture. The introduction of CB in pig manure could prolong the thermophilic phase, inhibit moisture reduce, facilitate the organic matter decomposition, reduce diethylene triamine pentaacetic acid (DTPA) extractable Zn and Cu contents in pig manure composts and increase ryegrass growth. The study indicated that the corn stalk CB prepared around 500°C was a suitable additive in pig manure composting.

Highly sensitive and selective colorimetric detection of cartap residue in agricultural products

The residue of pesticide has posed a serious threat to human health. Fast, broad-spectrum detection methods are necessary for on-site screening of various types of pesticides. With citrate-coated Au nanoparticles (Au NPs) as colorimetric probes, a visual and spectrophotometric method for rapid assay of cartap, which is one of the most important pesticides in agriculture, is reported for the first time. Based on the color change of Au colloid solution from wine-red to blue resulting from the aggregation of Au NPs, cartap could be detected in the concentration range of 0.05-0.6 mg/kg with a low detection limit of 0.04 mg/kg, which is much lower than the strictest cartap safety requirement of 0.1 mg/kg. Due to the limited research on the rapid detection of cartap based on Au NPs, the performance of the present method was evaluated through aggregation kinetics, interference influence, and sample pretreatment. To further demonstrate the selectivity and applicability of the method, cartap detection is realized in cabbage and tea with excellent analyte concentration recovery. These results demonstrate that the present method provides an easy and effective way to analyze pesticide residue in common products, which is of benefit for the rapid risk evaluation and on-site screening of pesticide residue.

Surface molecularly imprinted polymer capped Mn-doped ZnS quantum dots as a phosphorescent nanosensor for detecting patulin in apple juice

A Mn-doped ZnS quantum dots (QDs) based nanosensor for selective phosphorescent determination of patulin (PAT) was synthesized with 6-hydroxynicotinic acid (6-HNA) as dummy template via a surface molecular imprinting sol-gel process. FTIR and XRD indicated the successful graft of molecularly imprinted polymer (MIP) onto crystal QDs. Binding tests revealed that the MIP-QDs presented higher selectivity, adsorption capacity and mass transfer rate than non-imprinted polymers, demonstrating a specific recognition for PAT among competitive mycotoxins and its analogues with the imprinting factor of 2.02. The MIP-QDs could recognize PAT in a linear range of 0.43-6.50μmolL-1 with a detection limit of 0.32μmolL-1 and a correlation coefficient (R2) of 0.9945. Recoveries of 102.9-127.2% with relative standard deviations <4.95% were achieved in apple juice samples which were in good agreement with high-performance liquid chromatography (HPLC) (P>0.05). The results indicated a simple phosphorescent nanosensor for PAT detection in complex matrix.

High effective adsorption/removal of illegal food dyes from contaminated aqueous solution by Zr-MOFs (UiO-67)

UiO-67, a bifunctional adsorbent, was successfully applied to remove illegal food dyes (Congo red and Malachite green) from aqueous solution. The relevant adsorption conditions were optimized: pH 6, 120 min for contact time, and 10.0 mg L-1 adsorbent dose for Congo red. Adsorption behavior of UiO-67 exhibits a better fitting to pseudo-second-order kinetic model and Langmuir model. Moreover, the maximum adsorption capacities of Congo red (1236.9 mg g-1) and Malachite green (357.3 mg g-1) are higher than that of the most reported adsorbents. Thermodynamic analysis reveals that adsorption processes are spontaneous and endothermic in nature. Powder X-ray diffraction patterns, Fourier-transform infrared spectra and the X-ray photoelectron spectroscopy analysis indicates Zr-OH groups have positive influence on binding of target molecules. Whats more, UiO-67 could be reused without significant loss of its capacity after seven cycles. These results prefigure the promising potentials of UiO-67 in food safety risk management.

In-Situ Fixation of All-Inorganic Mo–Fe–S Clusters for the Highly Selective Removal of Lead(II)

The selective adsorption by suitable substrate materials is considered one of the most economical methods. In this work, an all-inorganic bimetallic Mo-Fe-S cluster is facilely achieved through in situ chemical fixation of tetrathiomolybdate (TTM) on Fe3O4 nanoparticles (NPs) at room temperature (donated as FeMoS NPs). The bimetallic building blocks on the obtained FeMoS NPs possess a monovacancy species of sulfur, endowing FeMoS NPs with a selectivity order of Zn2+, Mn2+, Ni2+ < Cd2+ ≪ Cu2+ < Pb2+ for metal-ion adsorption, a novel application for the Mo-Fe-S clusters. Particularly, with the highest selectivity for Pb2+ (Kd ≈ 107), which is about 3 × 103-1 × 106 times higher than those for other ions and has exceeded that of a series of outstanding sorbents reported for Pb2+, FeMoS NPs can efficiently reduce the concentration of Pb2+ from ∼10 ppm to an extremely low level of ∼1 ppb. This facile and rational fabrication of the Mo-Fe-S cluster with Fe3O4 represents a feasible approach to cheaply develop novel and efficient materials for the selective removal of lead(II).

The simultaneous detection and removal of organophosphorus pesticides by a novel Zr-MOF based smart adsorbent

Developing a smart adsorbent that can efficiently detect and remove toxic organophosphorus pesticides is important but still a great challenge. Here, a novel MOF-based smart adsorbent, Fe3O4@SiO2@UiO-67, was successfully fabricated via a versatile layer by layer assembly strategy and applied to the simultaneous selective recognition, detection and removal of glyphosate. The prepared smart adsorbent contains Zr–OH groups with high affinity for phosphate groups, endowing it with selective recognition and a higher adsorption capacity for glyphosate. Moreover, combining it with glyphosate leads to changes in the fluorescence intensity of the smart adsorbent, and incorporating silica impedes electron transfer between UiO-67 and the magnetic core, which can lead to the identification of the adsorbate and its concentration, and achieve a lower detection limit. Furthermore, using Fe3O4 as the magnetic core of the smart adsorbent facilitates the separation and removal process via an external magnetic field. Under optimized conditions, the obtained smart adsorbent exhibits excellent detection and adsorption performance with a high adsorption capacity (256.54 mg g−1), good reusability, and a low detection limit (0.093 mg L−1) for glyphosate, implying that the smart adsorbent has integrated the advantages of the individual components. All of this indicates that MOF-based smart adsorbents are promising for synchronous adsorption/detection and the removal of OPPs, presenting a viable option for monitoring water quality and treating wastewater.

Highly Specific and Sensitive Determination of Propyl Gallate in Food by a Novel Fluorescence Sensor

Propyl gallate (PG), one of the most widely used synthetic phenolic antioxidants in edible oil, cookies and fried food, has received extensive concern due to its possible toxic effects on human health. Herein, a novel fluorescence analytical method is firstly proposed to sensitively and selectively determine propyl gallate (PG) by utilizing the unique fluorescence quenching property of organic molybdate complex (OMC) formed by the specific reaction between MoO42- and PG to g-C3N4 nanosheets. Under the optimum conditions, the developed fluorescence sensor allows highly sensitive detection of PG in a wide range from 0.5 to 200 μg mL-1 with a detection limit of 0.11 μg mL-1, and possesses excellent specificity and good recoveries. All the analytical results indicate the present method provides an effective approach for rapid detection of PG in common products, which is beneficial for monitoring and reducing the risk of overuse of PG.