A kind of method for separating and recovering oxalic acid from oxalic acid waste liquid
A technology of waste liquid separation and oxalic acid, applied in the separation/purification of carboxylic acid compounds, chemical instruments and methods, alkali metal sulfite/sulfate purification, etc., can solve the problem of high recovery cost, increased production cost and decreased activity and other problems, to achieve the effect of high recycling efficiency, environmental protection and low cost
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Embodiment 1
[0026] The oil waste pickling wastewater was filtered while it was hot at 80°C to obtain 105kg of mixed filter residue of oxalic acid-sodium oxalate and 2.5m 3 Filtrate containing sodium sulfate. The filtrate is cooled to 5°C, sodium sulfate salt is crystallized, and about 10 kg of sodium sulfate salt crystals and its crystallization mother liquor are obtained by filtration, and the crystallization mother liquor is returned to the oil excrement pickling process. Take 100kg of oxalic acid-sodium oxalate mixed filter residue and put it into 1.5 times the theoretical amount of oxalic acid converted into oxalic acid, add 5mol / L HCl solution, stir at 60°C, absorb the floating superposition oil at rest, cool to 5°C to crystallize for 4h, and let the oxalic acid in it Crystals were precipitated and filtered to obtain oxalic acid crystals and mother liquor of oxalic acid crystals. The obtained oxalic acid crystals were mixed with water at a solid-to-liquid ratio of 1:2g / ml, heated to...
Embodiment 2
[0028] Take 1000 g of the oxalic acid-sodium oxalate mixed filter residue obtained in Example 1, add the oxalic acid crystallization mother liquor obtained in Example 1 at a solid-to-liquid ratio of 1:3 g / ml, and add 2 times the theoretical amount of oxalic acid converted from the mixed filter residue to slowly add 12 mol / L HCl concentrated hydrochloric acid, stir at 85°C, absorb the floating heavy oil in the upper layer, filter and remove the precipitated sodium chloride solid, cool the filtrate to 10°C to crystallize for 2 hours, and let the oxalic acid crystallize out. Filter to obtain oxalic acid crystals and oxalic acid crystallization mother liquor. Add the obtained oxalic acid crystals to the recrystallization mother liquor obtained in Example 1 at a solid-to-liquid ratio of 1:5 g / ml, raise the temperature to 60°C to dissolve the oxalic acid crystals, then cool to 5°C to allow the oxalic acid to recrystallize and precipitate, and filter to obtain recrystallized oxalic a...
Embodiment 3
[0030] Take 500 g of the mixed filter residue of oxalic acid-sodium oxalate salt obtained in Example 1, put it into 5 times the theoretical amount of oxalic acid, add 3mol / L HCl solution, stir at 65 ° C, and absorb the floating superposition oil in the upper layer statically, then filter to remove the precipitated chlorine After the solidification of sodium, the filtrate was cooled to 7°C and crystallized for 5 hours to precipitate the oxalic acid crystals, and filtered to obtain oxalic acid crystals and oxalic acid crystallization mother liquor. Add water to the obtained oxalic acid crystals at a solid-to-liquid ratio of 1:1 g / ml and stir, heat up to 100°C to dissolve the oxalic acid crystals, cool to 15°C to allow oxalic acid to recrystallize and precipitate, and filter to obtain recrystallized oxalic acid and oxalic acid recrystallized mother liquor. After recrystallized oxalic acid is dried, the oxalic acid product with a purity of 99.9% is obtained. After mixing the recry...
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