| 摘要 |
Process for removing chromium from tannery wastes The process comprises treating duly comminuted material from which chromium has to be removed 10 under countercurrent conditions. The material is loaded into a tank 1 where it is first treated with a formol solution 13 which is recycled, it being only necessary to add the water 11 and the formol 12 which degrades the wet pulp 14 which separated out in 2, which is passed to a reactor 3 where it is treated with a solution of recycled material 16 and another solution 15 which is rich in perborate. The pulp separates from the solution in 4 of which a fraction 17 is the effluent from the process from which chromium is recovered and the other is the one 16 which is recycled. The paste passes to a second reactor 6 where it is treated with a fraction of the recycled solution 21 and the remainder 15 of the enriched solution, the pulp is separated from the solution in 7, being washed with water 24, leaving a chromium-free paste 25 and a solution, a mixture of the filtrate and the wash water, which is recycled. The remainder 22 of the recycled solution is received in a mixer 5 in which the perborate 19 or the reagents are dissolved in order to obtain it and the pH of the solution is adjusted to 9 with soda or another alkali 20. <IMAGE>
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