Mechanical Behaviour Evaluation of Full Iron Tailings Concrete Columns under Large Eccentric Short-Term Loading.

In this study, full iron tailings concrete (FITC) was created using iron tailings from a tailings pond in Qian'an, China. Iron tailings account for 86.8% of the total mass of solid raw materials in the FITC. To enable large-scale use of FITC, a comprehensive investigation of the structural behaviour of full-iron tailing-reinforced concrete (FITRC) specimens is warranted. Therefore, eight rectangular reinforced concrete (RC) columns with conventional reinforced concrete (CRC) as a control were tested to investigate the effects of section dimensions, initial eccentricities, and concrete strengths, on the structural behaviour of FITRC columns under large eccentric short-term loading. The experimental and analytical results indicated that the sectional strain of the FITRC columns satisfied the plane-section assumption under short-term loading, and the lateral deflection curve agreed well with the half-sinusoidal curve. In addition, the FITRC columns exhibited a slightly lower cracking load and lower ultimate load capacity than the CRC columns, and the crack widths were larger than those of the CRC columns. The reduction in the load capacity observed in the FITRC was within the permissible range stated in the design code, thereby satisfying the code requirements. The deformation coefficients of the FITRC and CRC columns were identical, and the cracking and ultimate loads calculated according to the current code and theories were in good agreement with the measured results.

Microwave-assisted preparation of boron acid modified expanded graphite for the determination of chloramphenicol in egg samples.

A rapid and simple method for the synthesis of boron acid modified expanded graphite (B-EG) with the assist of microwave irradiation was developed. The synthesis process can be completed in one-step, where H2SO4 and H3BO3 were used as intercalating agent and KMnO4 was used as oxidizing agent. The obtained B-EG was worm-like and lamellar structure with plenty of small dispersed particles. The B-EG was successfully used as solid phase extraction absorbent for the enrichment and separation of chloramphenicol in egg samples, followed by liquid chromatography tandem mass spectrometry analysis. The predominant conditions affecting extraction efficiency were optimized. Under optimal conditions, the detection limit of the method was 0.27 ng g-1. The relative standard deviations of within-day and between-day were in the range of 2-6% and 2-8%, respectively. The method was successfully used to detect chloramphenicol in five egg samples. At the spiked concentration of 50 ng g-1, the satisfactory recoveries (87-94%) were obtained.

One-step solvothermal synthesis of magnetic Fe3O4-graphite composite for Fenton-like degradation of levofloxacin.

A novel Fe3O4-graphite composite was prepared, characterized, and investigated as a heterogeneous Fenton-like catalyst for the degradation of levofloxacin (LEV) in an aqueous solution. The results revealed that the Fe3O4-graphite composite exhibited excellent properties for the degradation and mineralization of LEV, achieving a nearly complete degradation of 50 mg L(-1) LEV in 15 min and 48% of total organic carbon removal in 60 min under optimal conditions. A large electronic conjugation structure exists in graphite, which may lead to the fast production of •OH radical species because of the easy reduction of Fe(III) to Fe(II). In addition, we observed that the graphite can degrade LEV in the presence of H2O2. Therefore, the synergistic results of the graphite structure and Fe3O4 magnetic nanoparticles (MNPs) may contribute to the high catalytic activity of the Fe3O4-graphite composite. Compared with pure Fe3O4 MNPs, lesser iron leaching of the Fe3O4-graphite composite was observed during the degradation of LEV. The degradation efficiency of LEV remained approximately 80% at the fifth recycling run, which indicates that the Fe3O4-graphite composite has potential applications in water treatment for removing organic pollutants.

Rapid preparation of expanded graphite by microwave irradiation for the extraction of triazine herbicides in milk samples.

In this study, we proposed a rapid and efficient method for the preparation of the expanded graphite (EG). The exfoliation process was accelerated by microwave irradiation, and the preparation time was greatly shortened. The obtained EG was worm-like in shape and exhibits well exfoliated structure. It was successfully applied as solid-phase extraction (SPE) adsorbent to extract and clean up the triazine herbicides in milk, followed by liquid chromatography tandem mass spectrometry (LC-MS) analysis. The parameters affecting the performance of extraction and LC-MS analysis were evaluated. Under the optimal conditions, the detection limits of triazines are in the range of 0.03-0.12 ng mL(-1). At the spiked level (0.4 ng mL(-1)), the recoveries of triazines are in the range of 82.5±2.5% to 97.5±7.5%. The proposed method was successfully applied to determine six triazines in six milk samples.

Determination of roxithromycin from human plasma samples based on magnetic surface molecularly imprinted polymers followed by liquid chromatography-tandem mass spectromer.

In this paper, a simple and reproducible method for the determination of roxithromycin in human plasma samples is proposed. The surface magnetic molecularly imprinted polymers (MMIPs) were utilized as sorbent. Roxithromycin was used as imprinted compound. The experimental results showed that the MMIPs had high affinity and selectivity toward roxithromycin. The extraction process was carried out in a single step by mixing the extraction solvent, MMIPs and human plasma samples by vortex. When the extraction process was completed, the MMIPs adsorbed the analyte were separated from the sample matrix by an external magnet due to the magnetism. The analyte eluted from the MMIPs was analysed by liquid chromatography-tandem mass spectrometry. Some main factors affecting the extraction of roxithromycin such as the amount of MMIPs, extraction solvent, extraction time, washing and elution conditions were optimized in this study. The calibration curve obtained by analyzing matrix-matched standards showed excellent linear relationship (r(2)=0.9997) in the concentration range of 10-1000ngmL(-1). The limit of detection and quantification obtained were 3.8 and 9.8ngmL(-1), respectively. The relative standard deviations of intra- and inter-day obtained were in the range of 3.9 %-5.5 % and 2.9 %-4.6 % with the recoveries ranging from 86.5 % to 91.5 %.

Sensitive detection of biothiols and histidine based on the recovered fluorescence of the carbon quantum dots-Hg(II) system.

In this paper, we presented a novel, rapid and highly sensitive sensor for glutathione (GSH), cysteine (Cys) and histidine (His) based on the recovered fluorescence of the carbon quantum dots (CQDs)-Hg(II) system. The CQDs were synthesized by microwave-assisted approach in one pot according to our previous report. The fluorescence of CQDs could be quenched in the presence of Hg(II) due to the coordination occurring between Hg(II) and functional groups on the surface of CQDs. Subsequently, the fluorescence of the CQDs-Hg(II) system was recovered gradually with the addition of GSH, Cys or His due to their stronger affinity with Hg(II). A good linear relationship was obtained from 0.10 to 20µmol L(-1) for GSH, from 0.20 to 45µmol L(-1) for Cys and from 0.50 to 60µmol L(-1) for His, respectively. This method has been successfully applied to the trace detection of GSH, Cys or His in human serum samples with satisfactory results. The proposed method was simple in design and fast in operation, which demonstrated great potential in bio-sensing fields.

Rapid preparation of molecularly imprinted polymers by microwave-assisted emulsion polymerization for the extraction of florfenicol in milk.

In this study, we proposed a rapid and simple method for the preparation of molecularly imprinted polymers (MIPs) by emulsion polymerization. The polymerization process was accelerated by microwave heating, and the reaction time was greatly shortened. The obtained MIPs were spherical in shape and exhibited a uniform morphology. The MIPs with selectivity and high affinity to florfenicol were successfully applied as solid-phase extraction materials to extract and clean up the florfenicol in milk, followed by liquid chromatography-tandem mass spectrometry (LC-MS) analysis. The parameters affecting the performance of extraction and LC-MS analysis were evaluated. The detection limit of the method was 4.1ngmL(-1). The relative standard deviations of intra- and inter-day were in the range of 3.5-4.7% and 3.9-7.5%, respectively.

Determination triazine pesticides in cereal samples based on single-hole hollow molecularly imprinted microspheres.

Single-hole hollow molecularly imprinted microspheres (h-MIMs) were prepared by hard template method and applied to extract six triazine pesticides in cereal samples, followed by HPLC-MS/MS detection. The synthesis mechanism of the h-MIMs has been studied. The h-MIMs exhibited bigger specific surface area and much higher binding capacity than the molecularly imprinted polymers prepared by precipitation polymerization (p-MIPs) and surface polymerization (s-MIPs). Besides, the adsorption rate of h-MIMs to prometryn was significantly higher than that of p-MIPs and s-MIPs. Owing to the hollow structure of the h-MIMs, more binding cavities were located on the inner and outer surfaces of the h-MIMs, which could facilitate the removal of template molecules from the polymers and the rebinding of the target molecules to the polymers. Under the optimal conditions, the detection limits of triazines are in the range of 0.08-0.16ngg(-1). At the spiked level (5ngg(-1)), the recoveries of triazines are in the range of 81±4% to 96±4%. The proposed method was successfully applied to determine six triazines in five cereal samples. Atrazine was found in two rice samples and a wheat sample with the contents of 5.1, 6.7 and 5.6ngg(-1), respectively. Ametryn and prometryn were found in a maize sample with the contents of 7.6 and 7.3ngg(-1), respectively.

Evaluation of intercalated α-zirconium phosphate as sorbent in separation and detection of sulfonamides in honey.

This paper presented a simple and effective solid-phase extraction method using α-zirconium phosphate intercalated by hexadecyl trimethyl ammonium bromide (α-ZrP-CTMAB) as a novel adsorbent. Surfactant-assisted method was applied to prepare α-ZrP-CTMAB whose sorbent properties and extraction efficiency were investigated. Four sulfonamides (SAs) in honey were selected as analytical models and finally determined by liquid chromatography-tandem mass spectrometry. The recoveries of SAs at three spiked levels (10, 100, 1000ngg(-1)) were in the range of 58.7-99.3% and the relative standard deviations ranged from 2.69% to 7.48%. The detection limits obtained were 0.25-0.5ngg(-1). Compared with other methods in the literatures, the proposed method reduced the consumption of organic solvents and simplified the sample preparation procedure for the analysis of SAs in honey. Therefore, modified α-ZrP showed great potential in the analysis of pollutants in complex samples.