[In-situ solvothermal polymerization of metal-organic framework/carbon-nitrogen nanosheet-coated solid-phase microextraction fiber for highly sensitive detection of pesticide residues in black tea].

Pyrethroids (PYs) and organochlorine pesticides (OCPs) are widely used to control pests and diseases in plants; however, they threaten human health. In this study, a metal-organic framework/carbon-nitrogen nanosheet composite nanomaterial (UiO-66/HOCN)-coated solid-phase microextraction (SPME) fiber was prepared by in-situ thermal polymerization. The prepared UiO-66/HOCN composite material was characterized by transmission electron microscopy, X-ray diffraction, nitrogen adsorption porosimetry, thermogravimetric analysis, and zeta potentiometry. The prepared UiO-66/HOCN composite-coated MSPE fiber was used for the enrichment and separation of OCPs and PYs, which showed good thermal and chemical stability as well as high extraction efficiency. Combined with gas chromatography-mass spectrometry (GC-MS), an efficient and sensitive method for the detection of trace levels of OCPs and PYs was developed. Under the optimal experimental conditions, wide linear ranges (0.1-800.0 ng/L), good linearity (≥ 0.9978), low limits of detection (0.03-0.30 ng/L), and acceptable repeatability (RSD ≤ 8.9%, n=3) were obtained. Typical black tea samples were analyzed by the developed method, and trace levels of aldrin (6.6 ng/g), α -endosulfan (54.7 ng/g), and bifenthrin (185.8 ng/g) were detected. The results demonstrate that the developed method has immense potential for the detection of pesticides in a complicated matrix.

Magnetic γ-cyclodextrin polymer with compatible cavity promote the magnetic solid-phase extraction of microcystins in water samples.

Microcystins (MCs), which are produced by eruptive cyanobacteria, seriously threaten the health of humans for their poisonousness. Herein, a facile strategy was introduced to synthesize the magnetic γ-cyclodextrin polymer (Fe3O4@PDA@γ-CDP) composite and set it as a novel adsorbent with excellent properties for the magnetic solid-phase extraction (MSPE) of MCs. The prepared Fe3O4@PDA@γ-CDP microspheres exhibit good aqueous dispersibility and highly affinity for MCs, thus contribute to an excellent extraction performance for trace MCs in water samples. Combined with HPLC-MS/MS, a handy, sensitive and efficient method was developed for detection of MCs in water samples, which shows good linearity (R2 ≥ 0.9992) in the range of 1.0-1000 pg mL-1, low limits of detection (0.8-2.0 pg mL-1, S/N = 3), satisfactory repeatability with the relative standard deviations (RSDs) lower than 6.2% (n = 5). At last, the proposed method was successfully applied for the extraction and detection of MCs in fresh water and sea water samples, which provides great potential of trace-level MCs determination in lake and sea water.

Metal-organic framework-coated stainless steel fiber for solid-phase microextraction of polychlorinated biphenyls.

For solid phase microextraction (SPME), effective immobilization of sorbent on a stainless steel fiber surface is very essential. But, it still remains challenging because the chemical inertness of stainless steel fiber. In this work, chemical bonding method was introduced to fabricate a series of metal-organic frameworks (MOFs)-coated stainless steel fibers, and some representative MOFs (ZIF-90 (Zn), MOF-199 (Cu), MIL-101 (Cr), MOF-5 (Zn))-coated stainless steel fibers were successfully synthesized. Such strategy can noticeably increase the mechanical and chemical stability, and prolong the service lifetime due to it combine the advantages of stainless steel fiber and chemical bonding method. The stability of MOF-ZIF-90 (Zn)-coated stainless steel fibers which were preparated by different methods (chemical bonding method, adhesive method and deposition method) were studied, and results showed the chemical bonding method proved the best stability. Based on the ZIF-90 (Zn)-coated fiber, the SPME-GC-MS method was developed for detecting traces of polychlorinated biphenyls (PCBs) and satisfactory results were obtained. The linear ranges were 0.01-600 ng L-1 and the coefficient of determination was higher than 0.993. The limits of detection for the PCBs were 0.0013-0.053 ng L-1. The recoveries for the spiked PCBs in the Minjiang water, soil and vegetable oil samples were in the range of 85.9-105.8%. The extraction capacity of the ZIF-90 (Zn)-coated stainless steel fiber prepared by chemical bonding method did not show measurable change under different temperatures or organic solvents for up to 5 days.

Regenerating fuel-gas desulfurizing agents by using bipolar membrane electrodialysis (BMED): effect of molecular structure of alkanolamines on the regeneration performance.

Alkanolamine sulfates are the heat-stable salts formed in the fuel-gas desulfurization by using alkanolamines, and they can cause the deterioration of absorption performance and loss of absorbents. In this paper, a method was reported to regenerate three alkanolamines (monoethanolamine, MEA; diethanolamine, DEA; and N,N'-dimethylethanolamine, DMEA) by using BMED. The effects of operation parameters (electrolyte concentration, alkanolamine sulfate concentration, and current density) on regeneration were analyzed on the basis of ion dimensions and intrinsic transport velocities, ion concentration, Donnan dialysis, ion orientation, and the interaction between alkanolamines and membranes. The process cost is estimated to be 0.48, 0.32, and 0.30 dollar/kg for MEA, DEA, and DMEA, respectively. BMED is not only feasible for alkanolamine regeneration but also environmental-friendly and economically attractive, especially as the bipolar membrane cost decreases and pollution control is strengthened.

Electrodialysis with bipolar membranes for sustainable development.

Electrodialysis with bipolar membranes (EDBM) is a kind of technology that integrates solvent and salt dissociation. It can realize salt conversion without second salt pollution or provide H+ and OH-/alkoxide ions in situ without salt introduction. Thus, it inherently possesses economical and environmental benefits. Moreover, its technological compatibility gives rise to new functions when it couples with other technologies, such as complexion, ion exchange, extraction, and adsorption. In view of the above peculiarities, EDBM has found many interesting applications in chemistry, food processing, biochemical industries, and environmental protection. However, its development has been restricted by such factors as lack of recognition of its contribution to industrial ecology, high membrane cost, insufficient research investment, and scarce operation experience. This paper compiles an introduction to this technology from the perspective of industrial ecology and conducts an extensive examination into EDBM applications. Its purpose is to gather synergic strength from academia, industry, and government to perfect EDBM for sustainable development.

Comparative study on the regeneration of flue-gas desulfurizing agents by using conventional electrodialysis (ED) and bipolar membrane electrodialysis (BMED).

Piperazine is an ideal desulfurizing agent but the heat-stable salts formed in desulfurization have caused secondary pollution and waste of resources. In the previous paper, a method was reported to regenerate piperazine by using BMED. To find the variety of that regeneration process, we performed experiments on the regeneration of piperazine by using ED. In comparison, ED has higher piperazine yield and current efficiency, and much lower voltage drop and energy consumption. However, its process cost is higher than that of BMED due to an extra expenditure for the base and its tank and pumps. The process cost is estimated to be 0.96 dollar/kg Pz for BMED and 1.14 dollar/kg Pz for ED. Notably, BMED has more environmental benefits and will be more economically attractive as the control on secondary pollution is strengthened and the bipolar membrane cost decreases.