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Nitrogen compounds in nonsaline waters

Nitrogen compounds in nonsaline waters

Aniline derivatives at the microgram level have been determined in natural waters by a spectrophotometric procedure involving diazotization with sulphuric acid and naphthol.

Nielen et al. used a strongly acidic cation-exchange resin for on-line preconcentration of polar anilines in water. The method could be automated and a detection limit for the nine anilines could be examined corresponding to 0.02–0.3 µg L−1.

Stuber and Henloar assessed the aqueous elution, selective concentration approach for isolating aromatic bases from water, and the factors controlling the concentration process identified using polymethylacrylic ester as an absorbent. The degree of concentration attainable depends on the ratio of the capacity of the natural form of the amine to that of the ionised form. Capacity factors of ionic forms of amines on polymethylacrylic ester resins are 20–250 times lower than those of the neutral forms and increase with the hydrophobicity of the amine.

In situ synthesis of polyaniline-fly ash cenosphere-based composites

The double-distilled aniline is preferred and polymerization of aniline under nitrogen environment is advantageous (Ramamurthy et al., 2012). In a typical synthesis, the FAC or Co/Ni-FAC (1.5 g) is dispersed in an acid solution (100 mL of 1M HCl solution) and a suitable amount of aniline (6 mL) is mixed at –30±2°C (Julabo chiller). A suitable amount of LiCl (6M) is also needed to be added to control the freezing temperature. The precooled ammonium persulfate (APS, 0.6M) solution also prepared in in HCl (1M, 100 mL) are added very slowly (~3 mL/min) to the aniline solution under stirring. The reaction needs at least 6 hours to complete. After that, the obtained precipitate is filtered and washed several times with DI water. Further, methanol washes are also required to remove nonreacting organic parts. Finally, it needs to be dried at 60±4°C in a vacuum oven for 12 hours. The cross-sectional schematic of PANI-metal/metal oxide-FAC composite structure is shown in.

The PU therefore exhibited a retardation effect on the curing reaction of the benzoxazine resin. That is, the processing window of the BA-a/PU resin mixtures is widened with the addition of the PU, similar to the addition of the epoxy diluent described in Sections 2.3 and 2.4. Therefore, one advantage of adding urethane to form BA-a/PU resin mixtures was the substantial modification in the chemorheological behaviors of the benzoxazine resin. The widest processing window was approximately 70-215 °C for BA-a/PU of 60/40 compared to the range of 90-195 °C of the neat BA-a.

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