Overview of methods
The purpose of magnetic iron determination is to circle the ores that can be recovered by a single low-intensity magnetic separation method, and the mFe/TFe≥85% is magnetic iron ore. Therefore, the strength of magnetic ferromagnetism is limited by the specific magnetization coefficient of 3000×10-6cm3/g. When the particle size of the specified ore sample is 0.075mm, the effective magnetic field (measured outside the casing) of the magnet is (900+-6cm3/g). Under this condition, pyrrhotite will be quantitatively selected as a magnetic mineral.
The method is to select the magnetic minerals in the sample with a magnet and then determine their iron content.
Reagent preparation
Sncl2100g/l HCl (1+1) solution.
Sulfuric acid: phosphoric acid: H2O = 15: 15: 70.
Sodium diphenylamine sulfonate 0.8 g of sodium diphenylamine sulfonate was dissolved in 950 ml of water, and then 50 ml of H2SO4 was added.
K2cr 2 o 7(k2cr 2 o 7)= 0.0358 mol/L. 。
The permanent magnet can be in the shape of a bar or a cylinder. Specification: length 10 ~ 12cm (if it is too short, it can be extended by iron pipe), with a diameter of about 2cm, and a closed glass tube sleeve or copper sleeve is covered outside.
Analytical method
Weigh 0.2 g sample. In a 12cm Petri dish, add 20mL of water to soak the sample, use a permanent magnet with a copper (or glass) sleeve to perform magnetic separation near the water surface, wash the magnetic part attracted by the permanent magnet with water, connect it to another Petri dish, and repeatedly perform magnetic separation until there is no magnetic iron to remove the entrained non-magnetic minerals, and transfer the obtained magnetic minerals to a 250mL conical flask. Add 40mL HCl( 1+ 1), heat until it is completely dissolved, and concentrate to about 10mL. Drop SnCl2 until yellow disappears, then drop 2-3 drops, rinse the bottle wall with water, cool with running water, add 6mL of saturated HgCl2 solution, stand for 3-5 minutes, and dilute to 65438 with water. Use blank test.
1.00% mFe 1mLK2Cr2O7 titration solution.
Matters needing attention
(1) The key point of this method is to strictly control the sample size and magnetic field strength.
(2) When washing the magnetic part attracted by the permanent magnet with water, do not rush directly to the magnetic sample, so as to avoid excessive impulse and loss of the magnetic sample.
(3) Transfer the magnetic part finally obtained to another conical flask filled with water for determination. After the magnetic minerals are flushed into the conical flask, the magnetic minerals are adsorbed by magnetic blocks and the water is poured out.
(4) For general samples, when the particle size is less than 0.075mm, the magnetite monomer can be dissociated by more than 90% ~ 95%, and the proportion of symbionts is small. If it is necessary to determine the magnetite content in rich symbionts, different treatments can be carried out according to their symbionts.
1) Magnetite is associated with pseudohematite. Pseudohematite is formed after partial oxidation of magnetite. At the same time, the contents of magnetite and pseudohematite are determined respectively, so that the contents of magnetite (Fe3O4) and pseudohematite (Fe2O3) can be calculated respectively by determining Fe2+ and Fe3+ in the selected magnetic iron.
2) Magnetite coexists with iron carbonate. With NH4Cl? The interference of iron carbonate can be eliminated by leaching iron carbonate with phenanthroline or AlCl3, filtering and external magnetic separation (note that the effective magnetic field strength is about 900Oe).
3) Magnetite coexists with ferric silicate. In addition to grinding the sample properly, the monomer of magnetite can be dissociated as much as possible, and the suitable leaching agent can be selected according to the type of associated iron silicate to leach and separate magnetite. If magnetite is associated with insoluble iron silicate, magnetite can be dissolved by HCl leaching at room temperature for 30 minutes, and iron silicate remains in insoluble residue. For the separation of soluble ferric silicate such as serpentine and olivine from magnetite, there is still a lack of specific selective solvents.
(5) For fine-grained disseminated oxide ore, more attention should be paid to the sample particle size and magnetic separation field strength, and the operation should be cautious. Even so, the results may still fluctuate greatly.
2. The phase analysis was carried out by WFC- 1 magnetic separator.
Overview of methods
Use WFC? 1 magnetic separator to separate magnetic iron minerals (the specified specific magnetization coefficient is 3000× 10-6cm3/g as the dividing line between magnetic iron and nonmagnetic iron). The magnetic part is determined by the same method as described above.
equipment
Magnetic separator WFC? Type 1. The magnetic separator consists of three parts: frame, transmission system and washing device. The permanent magnet and the magnetic separation tube are installed on the frame. The transmission system drives the permanent magnet to reciprocate up and down through the motor, and the cleaning device is used to clean the ore particles.
When the sample is magnetically separated in a magnetic separation tube, the magnetic force (or a component of the magnetic force) is perpendicular to gravity. Due to the magnetic force, the magnetic iron ore particles deviate from their vertical falling trajectory and are attracted to the wall of the magnetic separation tube near the magnetic pole. The main method of separating non-magnetic iron ore particles is gravity and water leaching. The permanent magnets on the frame have opposite magnetic poles and can reciprocate up and down, so that the magnetic field directions at the positions where magnetic iron ore particles are located are alternately exchanged, and the entrainment of magnetic iron to non-magnetic iron ore particles is reduced.
In order to make the magnetic force and mechanical force (opposite to the magnetic force) generated by the magnetic separator have high selectivity for magnetic and nonmagnetic minerals, the distance between the magnetic separator and the polar surface, the polar distance of each group of permanent magnets, the amplitude and speed of frame movement can be adjusted, and the elution flow rate is constant, generally 20mL/min.
In order to adapt to the separation of magnetic iron ore particles with severe oxidation and weak magnetism, a group of permanent magnets are respectively arranged at the upper and lower parts of the frame to prevent the phenomenon of missed separation.
The magnetic separator has four magnetic separation tubes, which can work simultaneously. For example, the figure 1.2 1 shows a single pipe.
Fig. 1.2 1 schematic diagram of magnetic separator.
1- water flow; 2- magnetic separation tube; 3- Water diversion rubber hose; 4- water stop clip; 5— Piston; 6- beaker; 7— Rubber plug; 8-Magnetic Iron Ore Particles
Analytical method
Weigh 0.1~ 0.5g sample (particle size < < 0.075mm) into a 50ml beaker, add 3 ~ 4ml water, and shake the ore particles evenly (be careful not to agglomerate the sample).
During magnetic separation, adjust the distance x between the magnetic separation tube and the pole face according to the required magnetic field strength (it can be measured according to the actual situation or estimated according to the formula Hx=H0e-cx, where H0 is the field strength of the pole face). Start the motor to make the permanent magnet move vertically at the frequency of 70 times/minute, and at the same time, inject water into the tube until the water level is 2 ~ 3 cm higher than the upper permanent magnet, then use the bottle washer to blow the sample out of the small beaker and enter the magnetic separation tube (2) through the small funnel (1). Unscrew the faucet (5) of the magnetic separation tube, so that the non-magnetic iron ore particles enter the 400mL beaker (6) with the water flow (remember, the water level must always be 2 ~ 3 cm higher than the upper permanent magnet). After all samples are moved into the tube, turn off the faucet (5), rinse the upper part of the tube wall with water, remove the funnel, tightly plug the rubber plug (7) connected with the water diversion hose (3) to the magnetic separation nozzle, and open the hose.
The magnetic iron ore particles entering the tube are adsorbed on the tube wall near the magnetic pole under the action of magnetic force, and the positive and negative directions of the magnetic field at the position where the magnetic iron ore particles are located alternate, so that the magnetic iron ore particles turn over at 180, and at the same time the non-magnetic iron ore particles are washed down by running water, thus realizing the quantitative separation of magnetic iron and non-magnetic iron in the sample.
When the water in the magnetic separation tube becomes clear and no non-magnetic ore particles fall from the magnet part (8), the magnetic separation is finished. At this time, close the water stop clamp and rubber tube of the faucet, unplug the rubber plug and then open the faucet to release the water in the magnetic separation tube (pay attention to slowly release the water when the water surface passes through the magnetic iron ore particles (8)). Remove the magnetic separation tube away from the permanent magnet, and blow the magnetic iron ore particles in the tube into another beaker with a washing bottle.
During the operation, samples are loaded from the first, second, third and fourth test tubes in turn. Under normal circumstances, after the fourth magnetic separation tube is installed, the magnetic iron in the first magnetic separation tube has been washed and purified, so magnetic iron ore particles can be taken out of the tube and put into another sample, and the average number of magnetic separation samples per hour can reach more than 10.
Matters needing attention
(1) Before each batch of samples starts magnetic separation, the magnetic separation tube must be cleaned with detergent to prevent ore particles from adhering to the tube wall during magnetic separation.
(2) For a few samples with serious oxidation or clay content, it is necessary to strictly control the magnetic field intensity of magnetic separation. During operation, weigh the sample and put it into a 100mL beaker, support a flat permanent magnet at the bottom of the beaker, add a small amount of water under the polar field strength of not less than 800 Oe, and shake the beaker several times. At this time, the magnetic iron ore particles are sucked at the bottom of the beaker, the non-magnetic ore particles are poured into the magnetic separation tube, the ore particles in the beaker are washed with a small amount of water, and then the non-magnetic ore particles are poured into the magnetic separation tube. Repeat this operation several times until the magnet in the cup is pure, and then take out the permanent magnet at the bottom of the cup.
(3) According to the data measured by magnetic separation method, the total amount of magnetic iron in the sample is mainly magnetite, but the mineral composition of the sample is different, and some of them also include pyrrhotite, maghemite, maghemite and all magnetite conjoined bodies with specific magnetization coefficient > 3000× 10-6cm3/g, which can be enriched by single low-intensity magnetic separation in industry.