Background and Overview

Arsenic is an essential trace element for animal growth. When animals lack arsenic, their fertility status will be affected, and the yield and quality of meat, eggs and milk provided to humans will be decreased, such as the decrease of amino acid absorption in poults, the decrease of conception rate in sows, and the decrease of milk production in goats. Organic arsenic, such as arsanilic acid, as an excellent arsenic-containing feed additive, is not only low in toxicity and easy to discharge, but also has almost no effect on meat quality and human health, and can promote the growth of meat livestock at the same time (weight gain), and also play the role of antibacterial (prevention of diarrhea and dysentery, etc.), antiparasitic, improve egg production rate and feed utilization rate, and improve the appearance quality of livestock products. In the 1950s, almost all large and medium-sized feed mills in the United States used organic arsenicals as feed additives. The azoarsine compounds in organic arsine (such as azoarsine-III) can be used as excellent indicators with good display effect and high sensitivity for zirconium, thorium and uranium plasma, and can detect low concentration of zirconium ions, which occupies a very important position in analytical chemistry. Organic arsenicals are also gaining attention in the field of pharmaceutical synthesis as a class of excellent antitumor drugs.

Benzylarsonic acid is used as a trapping agent in the flotation of cassiterite, wolframite and rare earth ore, and also as a trapping agent in the flotation of many kinds of metal oxide ores. It is the first effective trapping agent for wolframite and cassiterite fine mud in China.

Properties

Off-white powder, odorless, chemically stable, no deliquescence; soluble in hot water or alkaline solution, can form insoluble compounds with many kinds of metal ions. The industrial benzylarsonic acid is white powder with the mass fraction above 80%, containing a small amount of inorganic salts such as sodium chloride and sodium sulfate, and less than 1% of inorganic arsenic. Benzylarsonic acid is weakly acidic in water and produces H+ and benzylarsonic acid root by step ionization:

【Crystal type

The crystallographic information of benzylarsonic acid was obtained by X-ray single crystal diffraction test, which showed that it is monoclinic with space group P21/c. The asymmetric unit in the single crystal structure of benzylarsonic acid consists of a complete benzyl

The asymmetric unit in the single crystal structure of benzylarsonic acid consists of a complete benzylarsonic acid. We can clearly see the structure of the benzylic acid, where all the carbon atoms are in the same plane. At one end of the benzylic acid, a -AsO3H2 group is attached, where the As atom is connected in a tetrahedral configuration to the C atom on the benzylic acid, a double-bonded oxygen atom and two -OHs. The spatial orientation of the H atoms on the -OHs is related to their formation of O-H---O type hydrogen bonds with the oxygen atoms on the adjacent benzylic arsenate. The stacking diagram of benzylarsonic acid in the ac direction shows that the benzylarsonic acid molecules in the lattice can be stacked together regularly by intermolecular forces such as O-H---O and π-π stacking interactions between benzene rings. The asymmetric unit diagram of benzylarsonic acid and the stacking diagram in the ac direction are as follows:

[Synthesis].

1. Synthesis process reaction principle:

1) Reaction of arsenic trioxide and sodium hydroxide to produce sodium arsenite:

2) Reaction of benzyl chloride and sodium arsenite to form disodium salt of benzylarsonic acid:

3) After acidification and neutralization to p H = 2~3, a large amount of benzylarsonic acid is precipitated out.

2. Process flow:

Test in a 1 L four-necked flask according to the conditions of the test add arsenic trioxide, add water to make a slurry, slowly add pre-prepared sodium hydroxide solution, turn on the stirrer, heat up the temperature, wait until the temperature rises to 75 ~ 80 ℃ and maintain the temperature continue to stir, the reaction until the solution is a colorless transparent liquid, timing. Control the temperature, then slowly add benzyl chloride, maintain the temperature for arsonization reaction, stop until the specified time out of the material. The upper layer of crude benzyl alcohol was separated from the material solution, and the middle layer was transferred to a large beaker of 3 000 m L. The acidification was carried out by slowly adding the prepared dilute sulfuric acid solution under stirring until p H = 2~3, and the benzylarsonic acid formed white crystals and precipitated in large quantities. The product was obtained by filtration and washing. The mother liquor is concentrated, cooled and crystallized to precipitate sodium salts and other inorganic salts, and after filtration, the filtrate is reused to prepare sodium arsenite solution, as follows:

[Flotation of wolframite mechanism

The action of benzylarsonic acid and wolframite is chemisorption and chemical reaction into salt. Under acidic conditions, benzylarsonic acid exists in the form of H2B2-. Under alkaline conditions, benzylarsonic acid exists in the form of B2-. In pH 4-9, benzylarsonic acid exists in the HB-form. pH 4-9 is the best floatability. At this time benzylarsonic acid interacts with wolframite in HB- form. the chemical principle of chemisorption by HB-:

1) Molecular orbital theory explanation. Based on the chemical theory of molecular orbitals, HB- can be plotted on the wolframite

molecular orbital diagram of HB- interacting with Fe2+ and Mn2+ on the surface of wolframite grains:

Filling the d electrons of Fe2+ and the p electrons of O2- in HB- into the molecular orbitals, it can be seen that the energy of the whole system decreases greatly and the stability increases because the d electrons of Fe2+ and the p electrons of O2- in B- are mostly filled into the bonding orbitals. Similarly, the molecular orbital diagram of the interaction between Mn2+ and HB- can be drawn. It can be concluded that the interaction of HB- with wolframite grains is mainly to generate acid salts.

2) Explanation of soft and hard acid-base chemistry principle. From the rules of soft and hard acids and bases, it is known that Mn2+ and Fe2+ are hard acids and HB- is hard base. According to the basic rules of soft pro-soft and hard pro-hard, it can be assumed that HB- acts with the surface of wolframite grains by displacing water molecules in hydrated ions and generating complex ions with high stability, thus improving the hydrophobicity of the surface of wolframite grains: