Supported Liquid Membranes Based on Bifunctional Ionic Liquids for Selective Recovery of Gallium.

In this work, separation and recovery of gallium from aqueous solutions was examined using acid-base bifunctional ionic liquids (Bif-ILs) in both solvent extraction and supported liquid membrane (SLM) processes. The influence of a variety of parameters, such as feed acidity, extractant concentration and metal concentration on the solvent extraction behavior were evaluated. The slope method combined with FTIR spectroscopy was utilized to determine possible extraction mechanisms. The SLM containing Bif-ILs demonstrated highly selective facilitated transport of 96.2% Ga(III) from feed to stripping solution after optimization. During the evaluation of the separation performance of SLM for the transport of Ga(III), in the presence of Al(III), Mg(II), Cu(II) and Fe(II), 88.5% Ga(III) could be transported with only 6% Fe(II) and a nil quantity of other metals co-transported. SLM exhibited excellent long-time stability in five repeated transport cycles. Highly selective transport and separation performance was achieved using the SLM containing Bif-ILs, indicating considerable potential for application in Ga(III) recovery.

[Rapid determination of trace ciprofloxacin residue in milk samples using molecularly imprinted membrane extraction-high performance liquid chromatography-tandem mass spectrometry].

An enrofloxacin (ENR) molecularly imprinted membrane (MIM) was prepared with a polyvinylidenedifluoride (PVDF) membrane as the carrier, ENR as the dummy template molecule, α-methacrylic acid (MAA) as the functional monomer, ethylene glycol dimethacrylate (EGDMA) as the cross-linker, and a chloroform-methanol mixture solvent as the porogen. The MIM showed excellent selectivity, high adsorption capacity, and high adsorption rate for ciprofloxacin. Additionally, a method combining molecularly imprinted membrane extraction (MIME) and high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was developed and validated for the selective analysis of trace ciprofloxacin residue in milk samples. The sample pretreatment involved only a single step of protein precipitation. Ciprofloxacin showed good linearity in mass concentration range of 0.1-200 µg/L with a high correlation coefficient (r2>0.9996). The limit of detection (LOD, S/N=3) and limit of quantification (LOQ, S/N=10) were 0.02 µg/L and 0.1 µg/L, respectively. The relative standard deviations (RSDs) of interday and intraday precisions ranged from 3.3% to 7.9%. The ciprofloxacin recovery was in the range of 92.6%-119.1%. The results showed that the proposed method is simple and fast, with high accuracy and sensitivity, thus being suitable for the rapid detection of trace ciprofloxacin residue in milk samples.

Adsorption of Tetracycline by Shrimp Shell Waste from Aqueous Solutions: Adsorption Isotherm, Kinetics Modeling, and Mechanism.

The highly efficient removal of tetracycline (TC) from an aqueous solution was accomplished by using the raw shrimp shell waste (SSW) as an environmentally friendly adsorbent. The SSW without any treatment removed TC more efficiently than the SSW after being treated with HCl and NaOH solutions. The SSW was characterized using nitrogen adsorption-desorption isotherms, scanning electron microscopy alongside energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, a thermogravimetric-derivative thermogravimetry analyzer, and a ζ-potential analyzer. The maximum adsorption capacity of 400 mg/L SSW was 229.98 mg/g for 36 h at 55 °C. Both the Langmuir isotherm model and the pseudo-second-order kinetic model well described the experimental data. According to the values of the Gibbs free energy and enthalpy changes, the TC adsorption by SSW proved to be spontaneous and endothermic. The TC adsorption process was controlled by intraparticle diffusion and liquid film diffusion.

Rapid and sensitive determination of trace fluoroquinolone antibiotics in milk by molecularly imprinted polymer-coated stainless steel sheet electrospray ionization mass spectrometry.

Rapid analysis of trace analytes in complex biological samples is a great challenge for direct mass spectrometry, which suffers from low detection sensitivity. In this study, molecular imprinting technology was explored on the stainless steel sheet and integrated with the electrospray ionization method for direct sample analyses. The molecularly imprinted polymer-coated stainless steel sheet (MIPCS) was prepared and used as a solid-phase microextraction tip for rapid sampling of trace fluoroquinolone antibiotics in milk samples and then applied as an electrospray ionization tip to couple MS for sensitive detection. Our results shown that MIPCS could significantly enrich the trace fluoroquinolone antibiotics in milk samples. In our study, the extraction process of milk sample was completed within 30 min and the direct MS analysis was accomplished within 1 min. In addition, this proposed MIPCS-ESI-MS method showed a good linearity (R2>0.99) ranged from 1 to 1000 ng mL-1. The limits of detection (LODs) and limits of quantitation (LOQs) for the analytes range from 0.1 to 5 ng mL-1. The recoveries were in a range of 78.84%-103.04%. The relative standard deviation (RSD%) of inter-day and intra-day precision ranged from 7.00% to 10.4% and 4.46%-11.44% respectively. Overall, the proposed MIPCS-ESI-MS method could be feasibly used as a rapid and sensitive method for determination of trace analytes in complex food samples.

Synergistic Effect and Chlorine-Release Behaviors During Co-pyrolysis of LLDPE, PP, and PVC.

Plastic wastes are environmentally problematic and costly to treat, but they also represent a vast untapped resource for the renewable chemical and fuel production. Pyrolysis has received extensive attention in the treatment of plastic wastes because of its technical maturity. A sole polymer in the waste plastic is easy to recycle by any means of physical or chemical techniques. However, the majority of plastic in life are mixtures and they are hard to separate, which make pyrolysis of plastic complicated compared with pure plastic because of its difference in physical/chemical properties. This work focuses on the synergistic effect and its impact on chlorine removal from the pyrolysis of chlorinated plastic mixtures. The pyrolysis behavior of plastic mixtures was investigated in terms of thermogravimetric analysis, and the corresponding kinetics were analyzed according to the distributed activation energy model (DAEM). The results show that the synergistic effect existed in the pyrolysis of a plastic mixture of LLDPE, PP, and PVC, and the DAEM could well predict the kinetics behavior. The decomposition of LLDPE/PP mixtures occurred earlier than that of calculated ones. However, the synergistic effect weakened with the increase of LLDPE in the mixtures. As for the chlorine removal, the LLDPE and PP hindered the chlorine removal from PVC during the plastic mixture pyrolysis. A noticeable negative effect on dechlorination was observed after the introduction of LLDPE or PP. Besides, the chlorine-releasing temperature became higher during the pyrolysis of plastic mixtures ([LLDPE/PVC (1:1), PP/PVC (1:1), and LLDPE/PP/PVC (1:1:1)]. These results imply that the treatment of chlorinated plastic wastes was more difficult than that of PVC in thermal conversion. In other words, more attention should be paid to both the high-temperature chlorine corrosion and high-efficient chlorine removal in practical. These data are helpful for the treatment and thermal utilization of the yearly increased plastic wastes.

The dynamic CO2 adsorption of polyethylene polyamine-loaded MCM-41 before and after methoxypolyethylene glycol codispersion.

To reduce the cost of CO2 capture, polyethylene polyamine (PEPA), with a high amino density and relatively low price, was loaded into MCM-41 to prepare solid sorbents for CO2 capture from flue gases. In addition, methoxypolyethylene glycol (MPEG) was codispersed and coimpregnated with PEPA to prepare composite sorbents. The pore structures, surface functional groups, adsorption and regeneration properties for the sorbents were measured and characterized. When CO2 concentration is 15%, for 30, 40 and 50 wt% PEPA-loaded MCM-41, the equilibrium adsorption capacities were respectively determined to be 1.15, 1.47 and 1.66 mmol g-1 at 60 °C; for 30 wt% PEPA and 20 wt% MPEG, 40 wt% PEPA and 10 wt% MPEG, and 50 wt% PEPA and 5 wt% MPEG codispersed MCM-41, the equilibrium adsorption capacities were respectively determined to be 1.97, 2.22 and 2.25 mmol g-1 at 60 °C; the breakthrough and equilibrium adsorption capacities for 50 wt% PEPA and 5 wt% MPEG codispersed MCM-41 respectively reached 2.01 and 2.39 mmol g-1 at 50 °C, all values showed a significant increase compared to PEPA-modified MCM-41. After 10 regenerations, the equilibrium adsorption capacity for codispersed MCM-41 was reduced by 5.0%, with the regeneration performance being better than that of PEPA-loaded MCM-41, which was reduced by 7.8%. The CO2-TPD results indicated that the mutual interactions between PEPA and MPEG might change basic sites in MCM-41, thereby facilitating active site exposure and CO2 adsorption.