Sodium sulfide
Sodium sulfide is an activator of non-ferrous metal oxide ores, and when the addition amount is large enough, it is an inhibitor of sulfide ores. The preparation of sodium sulfide is to reduce sodium sulfate (Na2SO4) by burning coal, wood charcoal, etc. as reducing gases. The reaction formula is: Na2SO4+2C=Na2S+2CO2↑
Sodium sulfide is used as an inhibitor of sulfide ore in flotation operations, sodium sulfide is used to inhibit pyrite in the production practice of molybdenum separation, and molybdenite is flotated with kerosene as a collector, due to the good natural floatability of molybdenite is not inhibited by sodium sulfide, sodium sulfide inhibits pyrite, and qualified molybdenum concentrate is obtained after several selections.
When sodium sulfide is added to the slurry, the slurry is alkaline, which makes the surface of the sulfide minerals form a layer of hydrophilic hydroxide film and hydrophilic, so that the sulfide minerals are inhibited.
Zinc sulfate
The preparation of zinc sulfate is prepared by the reaction of zinc chips and dilute sulfuric acid in metal processing plants. Zinc sulfate is an inhibitor of sphalerite, the effect of single use is not very obvious, when shared with alkali, sodium cyanide, sodium sulfite, etc., the inhibition effect is strong, and the higher the pH value of the slurry, the better the inhibition effect.
Pure zinc sulfate does not turn yellow when stored in the air for a long time, and loses water in dry air to form a white powder. There are a variety of hydrates: a stable hydrate that equilibrates with water in the range of 0-39 °C is zinc sulfate heptahydrate, zinc sulfate 6 hydrate at 39-60 °C, and zinc sulfate monohydrate at 60-100 °C. When heated to 280 °C, various hydrates completely lose their crystal water, decompose into zinc oxide sulfate at 680 °C, further decompose above 750 °C, and finally decompose into zinc oxide and sulfur trioxide at about 930 °C. ZnSO4·7H2O and MSO4·7H2O(M = Mg, Fe, Mn, Co, Ni) form mixed crystals within a certain range. It reacts with alkali to form zinc hydroxide precipitate, and reacts with barium salt to form barium sulfate precipitate
The function of zinc sulfate: it is the main raw material for the manufacture of zinc barium white and zinc salt, and can also be used as a printing and dyeing mordant, a preservative for wood and leather, and an important auxiliary raw material for the production of viscose fiber and vinylon fiber. In addition, it is also used in the electroplating and electrolysis industries, and can also be used to make cables. Zinc sulfate inhibits sphalerite.
Cooling water is the largest amount of water used in industry. The cooling water in the closed circulating cooling system cannot corrode and scale the metal, so it is treated, and this process is called water quality stabilization, where zinc sulfate is used as a water quality stabilizer.
Sodium cyanide (potassium)
When the preferential flotation process is used for polymetallic deposits, sodium cyanide is used to inhibit sulfide minerals such as pyrite, sphalerite, chalcopyrite, etc., and the mixed use of sodium cyanide and zinc sulfate has a very good inhibition effect on sphalerite, pyrite when the amount of sodium cyanide is small, sphalerite can be inhibited when the amount is slightly large, and various copper sulfide minerals can be inhibited when the amount is increased.
In production practice, due to the toxicity of sodium cyanide, sulfur dioxide or sodium sulfite is often used instead, sulfur dioxide and sodium sulfite have weaker inhibition effect than sodium cyanide, but because of the low toxicity and easy to be oxidized by air, wastewater is easy to treat and often used. Another advantage is that minerals inhibited by sulfur dioxide and sodium sulfite are more easily activated by copper sulfate, while minerals inhibited by sodium cyanide are more difficult to activate.
Lime
Lime inhibition of pyrite: Lime inhibits pyrite due to the formation of hydrate films of calcium sulfate, calcium carbonate and calcium oxide on its surface.
To activate pyrite inhibited by lime, sodium carbonate and copper sulfate can be used, or sulfuric acid can be added to reduce the pH value of the slurry to 6~7, and butyl xanthate can be added to flotation pyrite.
Quicklime is a natural rock containing calcium carbonate, calcined at high temperature, and its main component is calcium oxide (CaO). Due to uneven heat or temperature control during calcination, it often contains under-flint lime or over-flint lime. The pulp yield of under-flint lime is small, the quality is poor, and the utilization rate is reduced, which will not bring harm. The hydration rate of the burned lime is greatly slowed down, and the hydration reaction with the water occurs only after hardening, resulting in a large volume expansion, resulting in local bulging and cracking on the surface of the hardened lime, which is called "ash blasting" in engineering. "Ash blasting" is one of the common problems in the quality of construction projects.
The process by which quicklime reacts with water to produce mature lime (Ca(OH)2) is called curing. In the project, a large amount of water (2~3 times the quality of quicklime) is matured into lime milk, and then flows into the ash storage tank through the screen and "stabilizes" for at least two weeks to eliminate the harm of overburned lime, and the paste obtained by removing excess water through precipitation is lime paste. It is also possible to pour appropriate water (60%~80% of quicklime amount) on each half meter high quicklime block, and the powder obtained by curing is called slaked lime powder. It is advisable to add water to the slaked lime powder slightly wet, but not into a clump.
The role of lime: lime has good water retention and plasticity, and is often used to improve the water retention of mortar in engineering to overcome the shortcomings of poor water retention of cement mortar. Lime has an inhibitory effect on pyrite. Lime has a slow condensation and hardening rate, low strength and poor water resistance. The drying shrinkage of lime is large, so it should not be used alone except for stucco.