[Simultaneous determination of 46 semi-volatile organic compounds in water by liquid-liquid extraction-gas chromatography-mass spectrometry].

Semi-volatile organic compounds (SVOCs) include polycyclic aromatic hydrocarbons (PAHs), phthalic acid esters (PAEs), organochlorine pesticides (OCPs) and nitrobenzenes (NBs). Most of them have carcinogenic, teratogenic, mutagenic and endocrine disrupting effects. Therefore, rapid and accurate determination of SVOCs in water is very important. As the most traditional pretreatment method, liquid-liquid extraction (LLE) has the advantages of wide extraction range, high extraction efficiency, simple operation and lower cost, which is very suitable for the simultaneous extraction of multiclass SVOCs. Dichloromethane has good solubility for most SVOCs, and is slightly soluble in water with low boiling point. It is a good broad-spectrum extractive solvent of organic compounds. But at present, there is no detection standard of SVOCs in water in China. In this study, three factors including nitrogen blowing temperature, pH of water sample and extraction time were optimized. It was aimed to establish a liquid-liquid extraction-gas chromatography-mass spectrometry (GC-MS) method for the simultaneous determination of the 46 SVOCs in water. At first, the effect of nitrogen blowing temperature (30, 35, 40 ℃) was investigated. The results showed that under different nitrogen blowing temperature, the recoveries of the 46 SVOCs were slightly different, but the differences were not significant. Considering the recovery and concentration efficiency, the nitrogen blowing temperature was finally set at 35 ℃. Dichloromethane was selected as the LLE solvent of the SVOCs and its extraction efficiency was investigated. The recoveries of the 46 SVOCs were satisfactory for the determination. Then sample pH (neutral and alkaline condition) was investigated. Most of the SVOCs in this paper have no obvious acid-base property. The extraction effect of water sample under neutral conditions was the best and the most stable, and under alkaline condition, the recovery of each substance was generally low. Finally, extraction time (7, 10, 15 min) was studied. In a certain range, with the increase of extraction time, the recovery also increased, but when the time increased to 15 min, the recovery of some compounds increased or decreased, and the time-consuming was longer, the recovery of most substances could meet the requirements when the extraction time was set to 10 min. The optimized experimental conditions were determined as follows: under neutral conditions, the water sample was extracted by dichloromethane for three times, each extraction time was 10 min, and concentrated at the nitrogen blowing temperature of 35 ℃. GC-MS was used for detection, and internal standard method was used for quantitative analysis. The results showed that the linearity of the method was good in the range of 20-2000 µg/L, the correlation coefficients (r 2) were no less than 0.9916, the limits of detection (LODs, S/N=3) ranged from 0.28 to 16.55 ng/L, and the limits of quantification (LOQs, S/N=10) ranged from 0.92 to 55.16 ng/L. The average recovery was 63.6%-125% at three spiked levels of 0.02, 0.2, 0.4 µg/L, with the relative standard deviations (n=6) ranging from 1.03% to 17.0%. This method was applied for the determination of 27 surface water samples in Jinan section of the Yellow River. The pollutants were mainly PAEs and PAHs, while NBs were not detected, only two kinds of OCPs were detected at some sites. The method is simple, universal, accurate and precise, and has low detection limit. It is suitable for the simultaneous determination of the 46 SVOCs in surface water and groundwater.

Biodiesel production in packed-bed reactors using lipase-nanoparticle biocomposite.

The development of appropriate reactors is crucial for the production of biodiesel. In this study, a packed-bed reactor system using lipase-Fe(3)O(4) nanoparticle biocomposite catalyst was successfully developed for biodiesel production based on soybean oil methanolysis. Emulsification before methanolysis improved the reaction rate. The lipase-nanoparticle biocomposite showed high activity and stability in the single-packed-bed reactor at an optimal flow rate (0.25 mL min(-1)). After 240 h of reaction, the conversion rate was sustained as high as 45%. The conversion rate and stability achieved using the four-packed-bed reactor were much higher than those achieved using the single-packed-bed reactor. The conversion of biodiesel was maintained at a high rate of over 88% for 192 h, and it only slightly declined to approximately 75% after 240 h of reaction. The packed-bed reactor system, therefore, has a great potential for achieving the design and operation of enzymatic biodiesel production on the industrial scale.

Gellan gel beads containing magnetic nanoparticles: an effective biosorbent for the removal of heavy metals from aqueous system.

This study describes an efficient adsorbent consisting of magnetic Fe(3)O(4) and gellan gum, which couples magnetic separation with ionic exchange for heavy metal removal. Adsorption kinetics analysis showed that the adsorption capacities were in an order of Pb(2+)>Cr(3+)>Mn(2+). Different experimental parameters studies indicated that adsorbent dosage, initial metal concentration, temperature and initial pH played important roles in adsorption process. Additionally, the Freundlich model gave a better fit to the experimental data than the Langmuir model. Chemical analysis of calcium ions released into the bulk solutions demonstrated that carboxyl group is critical for binding Pb(2+), Mn(2+) and Cr(3+). Furthermore, a high desorption efficiency was obtained by sodium citrate.