How to separate vanadium and chromium from wastewater?
Thread Content
I am currently working on a wastewater treatment project related to the treatment of wastewater generated in the production of vanadium pentoxide. Before treatment, the levels of total vanadium were 160 mg/l and those of Cr6+ were 1423 mg/l; after treatment, both vanadium and chromium levels in the effluent were below 1 mg/l. In the solution resulting from the treatment process, the vanadium level was 1.5 g/l and the Cr6+ level was 40 g/l. At this concentration, what methods can be used to separate vanadium from chromium? If the precipitation method is used, what are the minimum requirements for the concentrations of vanadium and chromium in water, and how are they separated?
You should clarify what type of solution is used for the analysis – whether it’s a sulfuric acid system, a chloride system, or something else. However, there is a method that can be used as a reference: ion-exchange membrane electrolysis. Vanadium acts as a cation, while hexavalent chromium functions as a complex anion; therefore, separation can be achieved through this membrane electrolysis method. :L :L :L If there’s anything wrong, please point it out, experts! ! ! !
The analysis solution is regenerated with alkali, so it is in an alkaline environment. The electrolysis cost is too high; I’m mainly considering using the chemical precipitation method
As far as I know, the most effective methods for separating vanadium from chromium are solvent extraction or ion exchange. You can refer to Cao Hongbin’s research.
I use resin to treat wastewater, and after that I want to use chemical methods for separation; however, separation using resin isn’t very effective.:)
It is better to use chemical methods for separation.
How to separate it? I just want to know the methods of separation using chemical methods
The ammonium salt precipitation method can be used; there are three conditions that yield three different products: ammonium polyvanadate of orange-red color is formed at a pH of 2–3, sodium vanadate of red color is formed at a pH of 4–6, and ammonium metavanadate is formed at a pH of 8–9. If that doesn’t work, I’ll think of another way to help you! !
I am also trying to separate vanadium and chromium, but the results are not good. The stock solution contains 3.5 g/l of vanadium and 11 g/l of chromium. I use calcium hydroxide to precipitate calcium hypovanadate in a pH range of 10–10.5, which allows the vanadium content in the solution to be reduced to 0.05 g/l. However, the precipitated calcium hypovanadate contains 5% chromium, and I am currently looking for ways to address this issue so that only a small amount of chromium is converted into calcium chromate, thereby meeting the requirements for separation. The preliminary idea for now is to raise the pH to 14 in advance to see what the effects will be. Theoretically, at a pH of 14, calcium will be completely converted into calcium hydroxide, and the solubility product of calcium hydroxide is lower than that of calcium chromate. Chromium will not turn into calcium. Calcium hydroxide then reacts with vanadium in the solution to form calcium orthovanadate. I also tried the method of using ammonium salts to precipitate vanadium mentioned upstairs, but it didn’t work. The most ideal outcome is to reduce vanadium levels to 0.6 g/l, but this far falls short of industrial requirements; industrially, vanadium levels need to be below 0.1 g/l. The reason is that once the chromium content in the solution reaches a certain level, it has a significant impact on the precipitation of vanadium as ammonium salts. I came across information on vanadium-titanium materials stating that when chromium is present in the solution, vanadium can be precipitated using ammonium salts by lowering the pH, but I have never been successful in doing this.
Patent application number: CN92111996.8; Date of patent application: 11/21/1992. Title: A method for separating and recovering vanadium and chromium from mixed vanadium-chromium wastewater as well as vanadium and chromium wastewater. Publication (announcement) number: CN1073414; Date of publication (announcement): 6/23/1993. Category: Chemistry； Date of metallurgical certification; Priority; Application (patent rights): Tang Yan, Liu Mingyang, Li Longyun, Zeng Zhaojun. Address: No. 20, Sandaoguai Street, Chengdu City, Sichuan Province, 610017. Inventors (designers): Liu Mingyang, Li Longyun, Zeng Zhaojun. International application; International publication; Date of entry into **; Patent agency; Agent. Abstract: A method for separating and recovering vanadium and chromium using chemical methods from mixed wastewater containing vanadium and chromium, as well as from wastewater containing only vanadium or only chromium. This chemical method is suitable for treating vanadium and chromium in wastewater from the metallurgical, chemical, and electroplating industries. For vanadium-chromium mixed wastewater, it is possible to achieve ideal separation, extraction, recovery, and utilization of both vanadium and chromium from either vanadium-containing or chromium-containing wastewater alone, thereby ensuring that the quality of the treated water meets **discharge standards**. In the past, mixed sedimentation methods were generally used for such water treatment; these methods require a large amount of space, and they generate a large volume of sludge that is difficult to recycle. This invention, however, employs a rapid sedimentation technique to separate vanadium and chromium from such wastewater, allowing for quick separation between the sludge and the liquid. As a result, less space is needed, the amount of sludge produced is reduced, and it is easier to recycle this sludge. This approach offers high economic value and is suitable for large, medium, and small-scale water treatment processes. A principal method for separating and recovering vanadium and chromium using chemical processes from mixed wastewater containing both vanadium and chromium, as well as wastewater containing either vanadium or chromium. This method is characterized by consisting of two separate stages: vanadium recovery and chromium recovery. Steps ① to ⑩ represent the vanadium recovery process, with the chemical reaction equation being: 3HVO₃↓[3] + FeCl₃↓[3] + 3N₂OH***Fe(VO₃)₃↓[3] + 3N₂Cl + 3H₂O ； (11)–(20) represent the chromium extraction process; the chemical reaction equations are as follows: 2H₂ + [2]CrO₄²⁻ + 3(NH₄)₂SO₄ → 3H₂SO₄ + 3(NH₄)₂SO₄ + 5H₂O + Cr₂(SO₄)₃ ； Cr↓[3](SO↓[4]) + 6N↓[2]OH***2Cr(OH)↓[3]↓ + 3Na↓[2]SO↓[4].
The comments from everyone upstairs are all great! I think separation doesn’t make much sense when the concentration is low; vanadium and chromium have similar physical properties, so ion exchange could be considered
Find a way to turn them into a solid state, and then use physical separation methods, such as filters and similar devices