Enhanced removal of aqueous Cr(VI) by the in situ iron loaded activated carbon through a facile impregnation with Fe(II) and Fe(VI) two step method: Mechanism study.

In this study, a novel in situ iron-loaded activated carbon (AFPAC) was prepared by a FeSO4/K2FeO4 impregnation and oxidation combination two-step supported on activated carbon for enhanced removal of Cr(VI) from aqueous solutions. Cr(VI) removal efficiency greatly increased by AFPAC more than 70% than that of fresh activated carbon (AC), which is due to rich iron oxides formed in situ and the synergistic effect between iron oxides and activated carbon. Cr(VI) adsorption behaviors on AFPAC under different water quality parameters were investigated. The maximum monolayer adsorption capacities for Cr(VI) by AFPAC are as high as 26.24 mg/g, 28.65 mg/g, and 32.05 mg/g at 25 °C, 35 °C and 45 °C at pH 4, respectively. Density functional theory (DFT) results showed that the adsorption energy of K2Cr2O7 on the surface of FeOOH was - 2.52 eV, which was greater than that on the surface of bare AC, and more charge transfer occurred during the adsorption of K2Cr2O7 on the surface of FeOOH, greatly promoting the formation of Cr = O-Fe. Cr(VI) removal by AFPAC included electrostatic attraction, redox reaction, coordinate complexation, and co-precipitation. Cr(VI) adsorption process on AFPAC consisted of the three reaction steps: (1) AFPAC was fast protonation and Cr2O72- would electrostatically attract to the positively charged AFPAC surface. (2) Cr2O72- was reduced into Cr2O3 by the carbons bond to the oxygen functionalities on activated carbon and the redox reaction process of FeSO4 and K2FeO4. (3) The inner-sphere complexes were formed, and adsorbed on AFPAC by iron oxides and then co-precipitation.

Characteristics and mechanisms of As(III) removal by potassium ferrate coupled with Al-based coagulants: Analysis of aluminum speciation distribution and transformation.

This study was carried out to investigate the enhanced removal of arsenite (As(III)) by potassium ferrate (K2FeO4) coupled with three Al-based coagulants, which focused innovatively on the distribution and transformation of hydrolyzed aluminum species as well as the mechanism of K2FeO4 interacted with different aluminum hydrolyzed polymers during As(III) removal. Results demonstrated that As(III) removal efficiency could be substantially elevated by K2FeO4 coupled with three Al-based coagulants treatment and the optimum As(III) removal effect was occurred at pH 6 with more than 97%. K2FeO4 showed a great effect on the distribution and transformation of aluminum hydrolyzed polymers and then coupled with a variety of aluminum species produced by the hydrolysis of aluminum coagulants for arsenic removal. During enhanced coagulation, arsenic removal by AlCl3 was main through the charge neutralization of in situ Al13 and the sweep flocculation of Al(OH)3, while PACl1 mainly depended on the charge neutralization of preformed Al13 and the bridging adsorption of Al13 aggregates, whereas PACl2 mainly relied on the sweep flocculation of Al(OH)3. This study provided a new insight into the distribution and transformation of aluminum species for the mechanism of As(III) removal by K2FeO4 coupled with different Al-based coagulants.

Highly efficient removal of arsenate and arsenite with potassium ferrate: role of in situ formed ferric nanoparticle.

It is well known the capacity of potassium ferrate (Fe(VI)) for the oxidation of pollutants or co-precipitation and adsorption of hazardous species. However, little information has been paid on the adsorption and co-precipitation contribution of the Fe(VI) resultant nanoparticles, the in situ hydrolytic ferric iron oxides. Here, the removal of arsenate (As(V)) and arsenite (As(III)) by Fe(VI) was investigated, which focused on the interaction mechanisms of Fe(VI) with arsenic, especially in the contribution of the co-precipitation and adsorption of its hydrolytic ferric iron oxides. pH and Fe(VI) played significant roles on arsenic removal; over 97.8% and 98.1% of As(V) and As(III) removal were observed when Fe(VI):As(V) and Fe(VI):As(III) were 24:1 and 16:1 at pH 4, respectively. The removal of As(V) and As(III) by in situ and ex situ formed hydrolytic ferric iron oxides was examined respectively. The results revealed that As(III) was oxidized by Fe(VI) to As(V), and then was removed though co-precipitation and adsorption by the hydrolytic ferric iron oxides with the contribution content was about 1:3. For As(V), it could be removed directly by the in situ formed particles from Fe(VI) through co-precipitation and adsorption with the contribution content was about 1:1.5. By comparison, As(III) and As(V) were mainly removed through adsorption by the 30-min hydrolytic ferric iron oxides during the ex situ process. The hydrolytic ferric iron oxides size was obviously different in the process of in situ and ex situ, possessing abundant and multiple morphological structures ferric oxides, which was conducive for the efficient removal of arsenic. This study would provide a new perspective for understanding the potential of Fe(VI) treatment on arsenic control.

One-step deep eutectic solvent strategy for efficient analysis of aflatoxins in edible oils.

BACKGROUND: Aflatoxins, a kind of carcinogen, have attracted increasing attention due to their toxicity and harmfulness to human health. Traditional methods for aflatoxins analysis usually involve tedious extraction steps with a subsequent derivatization process. Herein, a simple and efficient liquid-phase microextraction method based on deep eutectic solvents (DESs) for direct analysis of aflatoxins was developed. RESULTS: Adopting DESs as the extractant, we surprisingly found out that DESs could either achieve good extraction performance or play a similar role to the derivatization agent, achieving an enhancement of fluorescence intensity for direct analysis of aflatoxins by high-performance liquid chromatography combined with fluorescent detection. Under optimal conditions obtained by response surface methodology, the method provided satisfactory linear ranges (0.01-0.75 µg kg-1 for AFB1 and AFG1, 0.003-0.25 µg kg-1 for AFB2 and AFG2) with good determination coefficients (R2 > 0.9988), a low detection limit (0.0005-0.003 µg kg-1 ), and good recovery rates (72.05-113.54%). CONCLUSION: These results highlighted superiorities of the one-step DES strategy for analysis of aflatoxins in edible oils, providing insights for future development of efficient methods in food analysis. © 2020 Society of Chemical Industry.

Deep eutectic solvents used as extraction solvent for the determination of flavonoids from Camellia oleifera flowers by high-performance liquid chromatography.

INTRODUCTION: Camellia oleifera flowers are rich in flavonoids, but there has been little attention on their application. A simple and reliable method for determining the content of flavonoids in C. oleifera flowers would be very helpful for the utilisation of agriculture resources. OBJECTIVE: To develop an efficient analytical method for the determination of flavonoids in C. oleifera flowers by high-performance liquid chromatography-ultraviolet (HPLC-UV) detection. METHODOLOGY: Preparing an environmentally-friendly and effective solvent - deep eutectic solvents (DESs) - for compound extraction. Then investigating the influential factors of ultrasound-assisted extraction with DESs by the Box-Behnken design combined with response surface methodology. RESULTS: DES-5 synthesised with choline chloride and lactic acid (1:2) acquired excellent extractability for four flavonoids (quercetin 3-O-rhamnoside, kaempferol 3-O-rhamnoside and their aglycones) with different polarity. The proposed method, which could simultaneously determine four flavonoids with HPLC-UV detection for the first time, displays satisfactory recovery yields and high precision with inter-day relative standard deviation lower than 5.80%. CONCLUSION: DESs could be promising solvents for efficiently and selectively extracting bioactive compounds from plant materials, and the analytical method for flavonoids of C. oleifera flowers could provide reference value for its application and be used in other plant resources.

Limonoids from the fruits of Swietenia macrophylla with inhibitory activity against H2O2-induced apoptosis in HUVECs.

The fruits of Swietenia macrophylla (skyfruits) are commercially used as healthcare products to improve blood circulation. An investigation of active ingredients of skyfruits led to the isolation of four new limonoids, swietemacrolides A-D (1-4), together with ten known limonoids (5-14) and one proto-limonoid (15). Their structures were elucidated on the basis of MS and NMR data analysis. Swietemacrolide C (3) at the concentration of 10 µM showed significant protective effect on H2O2-induced apoptosis in human umbilical vascular endothelial cells (HUVECs), while swieteliacate D (5) displayed moderate anti-apoptotic activity.

Mexicanolide-type limonoids from the seeds of Swietenia macrophylla.

Three new mexicanolide-type limonoids, 3-O-propionylproceranolide (1), 6-O-acetylswietenin B (2), and 6-deoxyswietemahonin A (3), together with 15 known limonoids, were isolated from the seeds of Swietenia macrophylla (Meliaceae). The structures of those new compounds were established by extensive analysis of MS, 1D, and 2D NMR spectral data.

Fast and effective low-temperature freezing extraction technique to determine organotin compounds in edible vegetable oil.

Most organotin compounds that have been widely used in food packaging materials and production process show serious toxicity effects to human health. In this study, a simple and low-cost method based on high-performance liquid chromatography with inductively coupled plasma mass spectrometry for the simultaneous determination of four organotins in edible vegetable oil samples was developed. Four organotins including dibutyltin dichloride, tributyltin chloride, diphenyltin dichloride, and triphenyltin chloride were simultaneously extracted with methanol using the low-temperature precipitation process. After being concentrated, the extracts were purified by matrix solid-phase dispersion using graphitized carbon black. The experimental parameters such as extraction solvent and clean-up material were optimized. To evaluate the accuracy of the new method, the recoveries were investigated. In addition, a liquid chromatography with tandem mass spectrometry method was also proposed for comparison. The procedures of extracting and purifying samples for the analysis were simple and easy to perform batch operations, also showed good efficiency with lower relative standard deviation. The limits of detection of the four organotins were 0.28-0.59 µg/L, and the limits of quantification of the four organotins were 0.93-1.8 µg/L, respectively. The proposed method was successfully applied to the simultaneous analysis of the four organotins in edible vegetable oil. Some analytes were detected at the level of 2.5-28.8 µg/kg.