Regulation of polar microenvironment on the surface of tertiary amines functionalized polyacrylonitrile fiber and its effect on catalytic activity in Knoevenagel condensation

A dual-cycle regeneration to recover high-value and high-purity FePO4 from real wastewater for Li-battery application

The recovery of high-purity and high-value FePO4 raw materials from wastewater has great prospects in LiFePO4 battery industry due to the huge demand for new energy vehicle. However, the conventional in-situ FePO4 precipitation, as well as ex-situ PO43- adsorption-alkali regeneration, was incapable of efficiently obtaining high-purity products. To solve these problems, a dual-cycle regeneration method of Fe-NH2-polyacrylonitrile (PAN) adsorbent and H2SO4 desorbing solution was proposed to ex-situ FePO4 recovery from wastewater for Li-battery application. Benefitted from coordination interaction and electrostatic attraction, the maximum PO43- adsorption capacity of Fe-NH2-PAN reached 73.1 ± 0.4 mg/g. The average PO43- removal rate of continuous flow devices were 88.5% and 91.3% when treating low-P-concentration (0.22 mg/L) municipal wastewater (MW) and high-P-concentration (48.9 mg/L) slaughterhouse wastewater (SW) respectively. Furthermore, high-purity FePO4 analyzed by XRD spectra was achieved from the desorption solution at pH ∼1.6, resulting in the ultrahigh P recovery efficiencies of 91.4 ± 3.2%-96.3 ± 2.5% for SW and 82.7 ± 3.5% for MW. Besides, the LiFePO4/C electrodes made of recycled FePO4 exhibited a better discharge capacity (37.3 - 55.8 mAh/g) than that of commercial FePO4 agent (32.2 - 35.1 mAh/g) from 80 to 132 cycles, which showed the promising feasibility of recovering FePO4 from wastewater for Li-battery application.

Synthesis of FeOOH-Loaded Aminated Polyacrylonitrile Fiber for Simultaneous Removal of Phenylphosphonic Acid and Phosphate from Aqueous Solution

Phosphorus is one of the important metabolic elements for living organisms, but excess phosphorus in water can lead to eutrophication. At present, the removal of phosphorus in water bodies mainly focuses on inorganic phosphorus, while there is still a lack of research on the removal of organic phosphorus (OP). Therefore, the degradation of OP and synchronous recovery of the produced inorganic phosphorus has important significance for the reuse of OP resources and the prevention of water eutrophication. Herein, a novel FeOOH-loaded aminated polyacrylonitrile fiber (PAN_AF-FeOOH) was constructed to enhance the removal of OP and phosphate. Taking phenylphosphonic acid (PPOA) as an example, the results indicated that modification of the aminated fiber was beneficial to FeOOH fixation, and the PAN_AF-FeOOH prepared with 0.3 mol L^-1 Fe(OH)₃ colloid had the best performance for OP degradation. The PAN_AF-FeOOH efficiently activated peroxydisulfate (PDS) for the degradation of PPOA with a removal efficiency of 99%. Moreover, the PAN_AF-FeOOH maintained high removal capacity for OP over five cycles as well as strong anti-interference in a coexisting ion system. In addition, the removal mechanism of PPOA by the PAN_AF-FeOOH was mainly attributed to the enrichment effect of PPOA adsorption on the fiber surface's special microenvironment, which was more conducive to contact with SO₄•^- and •OH generated by PDS activation. Furthermore, the PAN_AF-FeOOH prepared with 0.2 mol L^-1 Fe(OH)₃ colloid possessed excellent phosphate removal capacity with a maximal adsorption quantity of 9.92 mg P g^-1. The adsorption kinetics and isotherms of the PAN_AF-FeOOH for phosphate were best depicted by pseudo-quadratic kinetics and a Langmuir isotherm model, showing a monolayer chemisorption procedure. Additionally, the phosphate removal mechanism was mainly due to the strong binding force of iron and the electrostatic force of protonated amine on the PAN_AF-FeOOH. In conclusion, this study provides evidence for PAN_AF-FeOOH as a potential material for the degradation of OP and simultaneous recovery of phosphate.

Polyphosphazene-Functionalized Microspheres as Efficient Catalysts for the Knoevenagel Reaction under Mild Conditions

Inspired by the formation of microspheres by hexachlorocyclotriphosphazene and 4, 4'-sulfonyldiphenol, polyphosphazene-functionalized microspheres were developed. Benefits from the supported supper basic phosphazene, the yield exceeded 99 % at room temperature in the manner of second-order reaction kinetics toward Knoevenagel reaction and was still maintained at 99 % after 16 runs. In the experimental temperature from 0 °C to 90 °C, the yield increased from 92 % to 99 %, reflecting that the catalyst had strong applicability under mild conditions. This behavior was conducive to energy conservation. Meanwhile, simple separation and recovery further enhanced this advantage. In addition, the catalyst was also found to be insensitive to aqueous solution or organic solvents such as toluene, THF, EtOH and CH₃ CN. This property gave the Knoevenagel reaction a vast choice. All these features exhibit that this novel catalyst is an attractive and applicable alternative in organic synthesis.