Synthesis of a magnetoactive compound based on iron(II) sulfate

Ferrofluid Synthesis Using Nitrosated Lignosulfonates

“…When studying the properties of nitrosated lignosulfonates we found for the first time that they are capable of peptising the coarse magnetite particles. ,− This allows obtaining stable ultrafine magnetite colloids with the properties of a ferrofluid.…”

“…The amount of sulfonic acid groups generally varies between 0.1 and 0.5 per phenylpropane unit. Nitrosation of lignosulfonates using nitrous acid leads to about 0.2–0.3 nitroso groups per phenylpropane unit ( c ). Nitrosated lignosulfonates are capable of forming chelate complexes with iron cations, holding a considerable amount of iron in an alkali-soluble state (3–4 iron cations per phenylpropane unit) .…”

“…Nitrosation of lignosulfonates using nitrous acid leads to about 0.2–0.3 nitroso groups per phenylpropane unit ( c ). Nitrosated lignosulfonates are capable of forming chelate complexes with iron cations, holding a considerable amount of iron in an alkali-soluble state (3–4 iron cations per phenylpropane unit) . At higher amounts of iron, coarse precipitation occurs followed by the formation of ferrofluid (see the text).…”

“…The following mechanism is suggested based on the published data. ,− Addition of sodium hydroxide to the mixture containing nitrosated lignosulfonates (LSN), iron(II) sulfate, and sodium nitrite, leads to the formation of the coarse precipitate. The latter is a complex composed of nitrosated lignosulfonates, iron(II) hydroxide, and nitrite anions: italicn normalFeSO 4 + italicm normalNaNO 2 + italick normalLSN + 2 italicn normalNaOH → Na italicm [ Fe ( OH ) 2 ] italicn false[ NO 2 false] italicm false[ LSN false] italick false↓ + italicn normalNa 2 SO 4 Electron spectroscopy studies revealed that 92–97% of nitrite anions are transferred from the solution to the precipitate . The precipitate is gradually densified and the oxidative–reductive reactions start to occur in it, leading to the formation of iron(III) cations.…”

“…Oxidation is accompanied by formation of the magnetic activity. The precipitate gradually acquires black color, characteristic for magnetite, Fe 3 O 4 , and the characteristic odor of ammonia appears: Na italicm [ Fe ( OH ) 2 ] italicn false[ NO 2 false] italicm false[ LSN false] italick → false[ Fe 3 normalO 4 false] italicn / 3 false[ LSN false] italick + italicm normalNH 3 false↑ + italicm normalH 2 normalO + italicm normalNaOH The formation of magnetite was proven by X-ray diffraction …”