Synthesis of a reactive lignin-based flame retardant and its application in phenolic foam

To improve the flame retardancy of phenolic foam from the perspective of sustainable development, it is a feasible way to add bio-based flame retardants into phenolic foam. Lignin has a similar structure to phenol, which provides a possibility to replace part of phenol. In this paper, we prepared a kind of reactive bio-based flame retardant based on enzymatic hydrolyzed lignin, in which side chain was chemically grafted with phosphorus and nitrogen and benzene ring would participate in the phenolic condensation reaction. According to elemental analysis and ICP-OES data, the content of nitrogen and phosphorus in modified lignin (NP-L) increased to 2.95% and 3.55% respectively. Compared with original lignin, the carbon residue rate of NP-L increased from 3.25% to 12.13% because of the presence of flame retardant elements N and P. Then lignin-based flame retardant was used to replace phenol for modifying phenolic foams (NPLPFX). The limited oxygen index (LOI) and compressive strength of phenolic foam were improved effectively by adding modified lignin when the substitution rate was less than 25%. The LOI and compressive strength of the modified phenolic foam with 5% replacement amount (NPLPF5) are 55.6% and 0.24 MPa, which increased by 88% and 60% compared with pure phenolic foam. The cone calorimetric data also showed that NPLPF5 had good flame retardancy, and the peak heat release rate and total heat release were significantly lower than PF. This work suggests a novel green strategy for improving the flame retardancy performance of phenolic foam and promoting the utilization of lignin.

Green chemical method for the synthesis of chromogenic fiber and its application for the detection and extraction of Hg2+ and Cu2+ in environmental medium

To advocate environment friendly detection idea, we adopted the green chemical method to synthesis the 1-(2 amino ethyl) piperidine functionalized polyacrylonitrile fiber (APF) and the chromogenic fiber 4-(2-pyridylazo) resorcinol (APF-PAR). The APF has high adsorption selectivity of Hg²⁺ and Cu²⁺, and the change of structure, surface morphology and thermo-stability before and after adsorption have been characterized by the infrared spectra, scanning electron microscope and thermogravimetric analysis. The APF achieved the adsorption equilibrium of Hg²⁺ just in 25 min and the adsorption capacity is 435.1 mg/g, while the adsorption equilibrium of Cu²⁺ costs 30 min and the adsorption capacity is 141.7 mg/g. The chromogenic fiber APF-PAR can recognize the Hg²⁺ and Cu²⁺ in 2 s, which benefits from the rapid mass transfer and small fluid resistance of the chelating PAN fiber. The color changed from orange to purplish red due to the variation of HOMO-LOMO energy gaps during the reaction which confirmed by the UV-vis absorption spectrum. It also has high selectivity and excellent adsorption performance, which provides more convenient, accurate, reliable and faster testing methods of Hg²⁺ and Cu²⁺ in environmental medium.

Electrocrystallization and solubility of mercury in alkaline solution

The chemical thermodynamics of mercury in aqueous sodium hydroxide solution has been investigated through electrochemical polarisation and solubility experiments. A review of thermodynamic data allowed determination of the Hg/HgO electrode potential. Cyclic voltammetry revealed a complex anodic reaction beginning with aqueous dissolution of elemental mercury and subsequent electrocrystallization of mercuric oxide. Cathodic sweeps showed dual reduction reactions, attributed to the presence of aqueous mercury and mercuric oxide. The solubility and hence activity of elemental mercury in sodium hydroxide solution was determined, otherwise known as the Sechenov salt effect. Sodium hydroxide salted mercury out of solution.

Cooking can decrease mercury contamination of a mushroom meal: Cantharellus cibarius and Amanita fulva

Mushrooms (Cantharellus cibarius and Amanita fulva) were blanched (parboiled) and pickled using different treatment conditions with the aim of carrying out the study into effect on removal of toxic mercury (Hg) accumulated in flesh. Blanching of fresh sliced C. cibarius caused leaching of Hg by approximately 15%, while loss of up to 35% was observed for sliced, deep-frozen fruit bodies. The rate of Hg leaching from the C. cibarius in practice was the same when blanched for 5 or 15 min irrespective of potable or deionized water used. Pickling of blanched C. cibarius with a diluted vinegar marinade had only a minor, if any, effect on removal of Hg and was without effect on blanched caps of A. fulva. Mercury was better extracted by boiling water from the fresh caps of A. fulva (56 ± 2% of the initial level in fresh caps) than from the fresh or frozen fruit bodies of C. cibarius. Total leaching rate of Hg from a pickled C. cibarius when fresh fruit bodies were processed was between 15 ± 5 and 37 ± 7% (median range 13-34%), and when deep-frozen fruit bodies were processed, it was between 37 ± 7 and 39 ± 8% (median range 34-39%). Pickling of the caps of A. fulva with diluted vinegar did not increase leaching of Hg. Blanching of mushrooms before future culinary use is a simple procedure recommended in reduction of contamination with Hg of cooked mushroom meal. Pickling had little if any effect on further removal of Hg from the initially blanched mushrooms.