•A novel phosphinic acid functionalized fiber adsorbent has been synthesized.•The PANAPCF shows high selectivity and efficiency for Hg2+ removal.•The PANAPCF can decrease Hg2+ concentration as low as 27 ppb.•The PANAPCF has excellent recyclability for more than 10 times.•This fiber can be used in a continuous flow process with high removal efficiency.A novel phosphinic acid functionalized polyacrylonitrile fiber (PANAPCF) was prepared and its adsorption properties were investigated. The PANAPCF shows excellent selectivity and efficiency for Hg2+ in the presence of other common metal ions, viz. Pb2+, Cd2+, Ag+, Zn2+, Cu2+, Ni2+, Co2+, Ca2+, Mg2+. Adsorption kinetics studies show that PANAPCF quickly captures Hg2+ and achieves equilibrium within 3 h. In addition, PANAPCF is effective over a wide range of pH values (from 3 to 11). The maximum adsorption capacity for Hg2+ as calculated by a Langmuir isotherm model was 434 mg g−1. PANAPCF could also efficiently remove Hg2+ from practical wastewater and the concentration of Hg2+ could be decreased as low as 27 ppb, which is below the maximum contamination level of 50 ppb for mercury containing wastewater in China. Furthermore, the PANAPCF can be used to remove Hg2+ from a flow process with a 99% removal efficiency even after ten cycles. Finally, XPS analysis proved that the PO/POH and –NH– functional groups play a major role in the adsorption mechanism.Download high-res image (107KB)Download full-size image

Three chiral pyrrolidine functionalized polyacrylonitrile fiber catalysts have been designed, prepared, and evaluated for their catalytic performance in asymmetric Michael addition of ketones to nitrostyrenes in water. With the optimized catalysts and conditions in hand, their reaction scope for nitrostyrenes was explored. Then the fiber catalysts were further applied to a packed-bed reactor for continuous-flow Michael addition. Based on the fact that organic solvent can inhibit the catalytic activity, a novel microenvironment catalytic mechanism is proposed.

A series of polyacrylonitrile fiber-supported quaternary ammonium salts (PANF-QAS) were prepared and applied to the catalytic reduction of aldehydes, ketones, azides, and benzyl halides in water using NaBH4 as the reducing reagent in a highly efficient, economic, and environmentally benign way. The structure–activity relationships were investigated, which showed that the catalysts made up of quaternary ammonium salts with longer alkyl chains, larger cationic radii and better lipophilicity speed up the reduction reaction to afford the products in excellent yield. Moreover, the optimized catalyst can be applied to the reduction of 1-naphthaldehyde in a continuous flow process with outstanding reactivity and recyclability.

A thiadiazole-functionalized polyacrylonitrile fiber (DPTD-PANPF) qualitative colorimetric sensor was prepared for the first time, and its absorption properties were investigated in detail. The obtained sensor exhibits excellent chelating selectivity towards Ag+ without interference by other co-existing ions (Pb2+, Hg2+, Cd2+, Zn2+, and Cu2+) and generates a remarkable visual color change from yellow to red-brown over a wide pH range from 3 to 12. The DPTD-PANPF for Ag+ has a naked-eye detection limit of 11 ppb (only one in ten thousand of that of the small molecule DPTD) and a much higher saturation absorption capacity of 149 mg g−1. Moreover, the fiber can be repeatedly used more than 50 times. In summary, this fiber sensor possesses the advantages of excellent selectivity, lower detection limit, outstanding absorption capacity and reusability to detect and remove Ag+ from water.

A bis(2-pyridylmethyl)amino group-modified polyacrylonitrile fiber (BPEN-PANF) was firstly prepared. The BPEN-PANF displays excellent selective complexation affinity in a 1:1 binding stoichiometry for the common toxic heavy metal ions, viz. Pb2+, Hg2+, Cd2+, Ag+, Zn2+, Cu2+, Ni2+, Co2+, and Cr3+. Meanwhile, it was significant that a much weaker binding ability was expressed for other light metal ions (Ca2+, Al3+, and Mg2+). Taking Pb2+ as an example, the maximum absorption capacity was as large as 303 mg g−1 calculated by the Langmuir isotherm model with an equilibrium time of 60 min. And the BPEN-PANF exhibits high absorption capacities for Pb2+ over a wide range of pH values from 3 to 11. Furthermore, it has an absorption limit of 4.76 ppb which is much lower than the drinking water standard of 10 ppb issued by the WHO. More positively, it can be easily recycled by filtration from the metal ion solutions and reused more than 20 times. In summary, the BPEN-PANF has the advantages of having inexpensive raw materials, simple preparation, high selectivity for heavy metal ions, and excellent recyclability and reusability, which surely indicates that the BPEN-PANF is a particularly useful material for rapid and simultaneous removal of heavy metal ions from polluted water.

Four aminopyridine (AP) functionalized polyacrylonitrile fibers (PANAPFs) were developed. UV–vis, FTIR, EA, and SEM were used to demonstrate the successful preparation of the fiber catalysts. Among the prepared catalysts, the PANp-AP-3F (with a C3 chain linker) and PANp-AP-6F (with a C6 chain linker) exhibited the best catalytic activity to efficiently catalyze the Gewald reaction of ethyl cyanoacetate and 2,5-dihydroxy-1,4-dithiane in water with yields up to 92% under a low catalyst dosage of 1 mol %. The influences of the position and length of the linker, i.e., the carbon chain between the fiber backbone and the aminopyridine moiety, on the catalytic activities were investigated in detail. In addition, the selected catalyst PANp-AP-3F was applied to the Gewald reaction of a series of active nitriles and 2,5-dihydroxy-1,4-dithiane and reused without further treatments. A possible mechanism and a microenvironment promoting process were conceived to explain the excellent catalytic properties of this catalytic system. Furthermore, the PANp-AP-3F performed well in a scaled-up experiment indicating its potential application in industry.Keywords: 3-Substituted 2-aminothiophene; Aminopyridine; Fiber catalyst; Gewald reaction; Microenvironment; Polyacrylonitrile fiber; Water

A series of fiber supported acid–base bifunctional catalysts (FABCs) were developed by successive grafting of acrylic acid and 4-vinylpyridine onto the polypropylene fiber (PPF). The FABCs can efficiently catalyze a number of reactions whose key steps involve in nucleophilic addition. The obviously enhanced activities of the bifunctional catalysts compared with that of the individual fiber supported acid or base upon the nitro-aldol and Knoevenagel reactions indicate that the FABCs perform in a cooperative catalyzing model and their activities can be easily tuned by controlling the acid–base ratio. An optimized bifunctional catalyst was successfully applied to the aqueous Gewald, tandem Michael–Henry reaction and one three-component reaction with excellent catalytic performances. In addition, this newly developed bifunctional fiber catalyst also exhibits excellent recyclability and reusability with simple treatment.Keywords: Aqueous catalysis; Bifunctional catalyst; Heterogeneous catalyst; Nucleophilic addition; Polypropylene fiber (PPF)

A series of thiourea modified fibers were prepared and characterized. The N-(2-aminoethyl)thiourea functionalized polyacrylonitrile fiber (AETU-PANF) was then evaluated for palladium absorption. The absorption process follows a pseudo-second-order model and the equilibrium data fit well to the Langmuir isotherm model. The maximum absorption capacity according to the Langmuir model was 169.2 mg g−1 with an absorption limit of 0.03 ppm. Wetted AETU-PANFs exhibited excellent absorption properties in organic solutions and the sorption rates were higher in organic solvents than in aqueous solutions. This is due to a special microenvironment that is formed inside the AETU-PANFs. The AETU-PANFs were also used to remove palladium from an organic solution containing active pharmaceutical ingredients. The Pd content was reduced from 310 ppm to 0.07 ppm.

A multistep experiment for a synthesis laboratory course that incorporates topics in organic synthesis, chemical analysis, and instrumental analysis was developed. Students prepared a tertiaryamine-functionalized polyacrylonitrile fiber (PANTF), and it was subsequently utilized as an immobilized catalyst in a three-component condensation reaction among an aromatic aldehyde, malononitrile, and α-naphthol in ethanol to synthesize substituted 2-amino-2-chromenes in one pot. The fiber catalyst exhibits the advantages of high yield, excellent recyclability and reusability, simple post-treatment, and environmental friendliness. Thus, students were able to apply the concept of green chemistry through catalysis. Moreover, this comprehensive experiment involves a number of unit operations, such as vacuum distillation, filtration, recrystallization, and acid–base titration, which can train the fundamental operation capability of students, and improve their experimental skills.Keywords: Analytical Chemistry; Green Chemistry; Hands-On Learning/Manipulatives; Laboratory Instruction; Organic Chemistry; Synthesis; Upper-Division Undergraduate;

A colorimetric Hg2+ sensor based on the porphyrin-functionalized polyacrylonitrile fiber (CTAPP–PANAF) was prepared and investigated. This functional fiber sensor shows excellent selectivity and sensitivity towards Hg2+ over other common metal ions (Pb2+, Ba2+, Cd2+, Ag+, Zn2+, Cu2+, Ni2+, Co2+, Fe3+, Mn2+, Cr3+, Ca2+, Al3+ and Mg2+). Upon the addition of Hg2+, a remarkable visual color change from red-brown to dark-green and significant detectable changes in the FTIR, UV and FL spectra of CTAPP–PANAF were observed. The naked-eye detection limit is as low as 20 ppb (1 × 10−7 mol L−1), which is below the maximum contamination level of 50 ppb for mercury containing wastewater in China. This functional fiber sensor also exhibits excellent reusability and recyclability and can be repeatedly used more than 50 times. The Hg2+ complexed sensor can be easily separated from the aqueous solution by simple filtration and reversed back by treating with dilute HCl. Furthermore, real water sample testing confirms the practical application of CTAPP–PANAF. In a word, the fiber sensor possesses the advantages of simplicity, rapidity, and reusability as well as high selectivity and sensitivity.

A DMAP (4-dimethylaminopyridine) functionalized polyacrylonitrile fiber catalyst (PANDMAPF) was prepared and used to efficiently catalyze three-component condensation reactions among an aldehyde, malononitrile and α-naphthol in water to afford the corresponding substituted 2-amino-2-chromenes. The PANDMAPF exhibited excellent catalytic activities in water and methanol, but failed to show any catalytic activity in ethanol and solvents with low polarity. In other words, water can turn the reaction on but ethanol shuts it off. This differs greatly from the same reaction catalyzed by free DMAP or by a tertiary amine functionalized polyacrylonitrile fiber. The PANDMAPF catalyst is applicable to a wide range of aromatic aldehydes (80–99%). Moreover, this newly developed fiber catalyst also exhibited excellent recyclability and reusability (up to seven times) without any additional treatment.

Two sulphur-containing 4-aminonaphthalimide derivatives were investigated as Hg2+ fluorescent chemosensors. In CH3CN, both sensors present a remarkable fluorescence enhancement to Cu2+ and Fe3+, but a selective fluorescence quenching to Hg2+ among the other metal ions. A cation-π interaction between Hg2+ and the naphthalimide moiety was proposed and confirmed by the density functional theory(DFT).

A colorimetric Hg2+ sensor based on the porphyrin-functionalized polyacrylonitrile fiber (CTAPP–PANAF) was prepared and investigated. This functional fiber sensor shows excellent selectivity and sensitivity towards Hg2+ over other common metal ions (Pb2+, Ba2+, Cd2+, Ag+, Zn2+, Cu2+, Ni2+, Co2+, Fe3+, Mn2+, Cr3+, Ca2+, Al3+ and Mg2+). Upon the addition of Hg2+, a remarkable visual color change from red-brown to dark-green and significant detectable changes in the FTIR, UV and FL spectra of CTAPP–PANAF were observed. The naked-eye detection limit is as low as 20 ppb (1 × 10−7 mol L−1), which is below the maximum contamination level of 50 ppb for mercury containing wastewater in China. This functional fiber sensor also exhibits excellent reusability and recyclability and can be repeatedly used more than 50 times. The Hg2+ complexed sensor can be easily separated from the aqueous solution by simple filtration and reversed back by treating with dilute HCl. Furthermore, real water sample testing confirms the practical application of CTAPP–PANAF. In a word, the fiber sensor possesses the advantages of simplicity, rapidity, and reusability as well as high selectivity and sensitivity.

A thiadiazole-functionalized polyacrylonitrile fiber (DPTD-PANPF) qualitative colorimetric sensor was prepared for the first time, and its absorption properties were investigated in detail. The obtained sensor exhibits excellent chelating selectivity towards Ag+ without interference by other co-existing ions (Pb2+, Hg2+, Cd2+, Zn2+, and Cu2+) and generates a remarkable visual color change from yellow to red-brown over a wide pH range from 3 to 12. The DPTD-PANPF for Ag+ has a naked-eye detection limit of 11 ppb (only one in ten thousand of that of the small molecule DPTD) and a much higher saturation absorption capacity of 149 mg g−1. Moreover, the fiber can be repeatedly used more than 50 times. In summary, this fiber sensor possesses the advantages of excellent selectivity, lower detection limit, outstanding absorption capacity and reusability to detect and remove Ag+ from water.