The influence of the nitrosation conditions of lignosulfonates on the synthesis of magnetoactive compound

Abstract

The infl uence of reagent consumption (sodium nitrite and nitric acid) and nitrosation time of lignosulfonic acids on their peptization activity during subsequent synthesis of a magnetoactive compound on the basis of iron(II) sulfate with the properties of a magnetic fl uid was determined. Ultradisperse magnetoactive compounds (MCs) [particles of magnetite (Fe 3 O 4 ) or ferrites of composition MFe 2 O 4 ] are dispersed phase of magnetic fl uids, which have fl uidity and can interact with a magnetic fi eld [1, 2]. Magnetic fl uids are synthesized by the methods of dispersion and condensation. The condensation methods are based on the reaction involving di-and trivalent iron cations [3-5]: 2Fe 3+ + Fe 2+ + 8OH -→ Fe 3 O 4 ↓ + 4H 2 O.The condensation performed at the ratio of salts Fe 3+ :Fe 2+ = 2 : 1 at 70°С and constant agitation results in the formation of colloidal particles. With the use of ammonium hydroxide, the temperature may be decreased to 25-40°С [6-9].In [10, 11], magnetite-based ferrofl uid was obtained from di-and trivalent iron salts after prolonged thermal treatment; stabilizers were lignosulfonates (LSs) instead of the commonly used oleic acid.Methods of the prepration of magnetically active compound of the magnetite type based solely on iron(II) salt are rare. Belikov et al.[12] suggested a method including precipitation of iron(II) carbonate from a solution of iron(II) salt and its subsequent treatment within 55-60°С for 1 h. However, magnetite synthesized by the above method has low relative magnetic susceptibility (RMS).The nitrosation of LSs allows preparation of iron(II)sulfate-based MC in the form of ultradisperse colloidal solution with high RMS value.In the study, the optimal conditions of the LS nitrosation were determined to obtain MC with maximum peptization ability. EXPERIMENTALWe used in experiments 65% nitric acid, sodium hydroxide, iron(II) sulfate heptahydrate (analytical purity grade), and technical lignosulfonates. From these reagents we prepared aqueous solutions of the following concentrations: 1 M NaOH, 10% HNO 3 , 2.5g l -1 NaNO 2 , and 18.6 g l -1 LS. A solution of iron(II) sulphate was prepared in a 200-ml volumetric fl ask. To do this, 5.56 g of FeSO 4 ·7H 2 O were dissolved in distilled water, 16 ml of 10% acetic acid was added to suppress hydrolysis, and then distilled water was added to the mark.LSs were nitrosated in a 100-ml volumetric fl ask containing 4 ml of a solution of initial LSs, to which a prescribed volume of 10% nitric acid, 80 ml of distilled water, and a prescribed volume of the solution of sodium nitrite were added. Then, distilled water was added to the mark and the reaction mixture was kept for a necessary time.The MC synthesis was performed as follows. Into a tube, a 10 ml of a solution of initial or nitrosated LSs was introduced, to which 2 ml of a solution of iron(II) sulfate

Ferrofluid Synthesis Using Nitrosated Lignosulfonates

“…2 and 10 are only partially peptised, while low molecular mass lignosulfonates (nos. 1,6,12,13,18) practically lack the peptising ability.…”

“…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.…”

“…Modification of lignosulfonates by nitrosation allows obtaining magnetoactive compound based on iron(II) sulfate (see Figure ). 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 .…”