Chromium slag passivation pretreatment method

The invention discloses a chromium slag passivation pretreatment method. The method comprises the following steps that firstly, tryptone, peptone, beef extract, yeast extract, NaCl and glucose are dissolved into distilled water to prepare a basic solution; KH2PO3, urea and NiCl2 are dissolved into the basic solution to prepare a treatment agent, wherein the concentrations of all components are 1-5g/L, 20-120g/L, 0.001g-0.01g/L correspondingly, and pH value is adjusted by using dilute sulfuric acid and NaOH; the treatment agent is mixed uniformly with chromium slag at a liquid-solid ratio of 1:1-3:1 to be left to stand for 4-8 days and stirred once per 2-6 hours, so that chromium slag slurry is obtained; and 1000-2000g/LCaCl2 solution is uniformly stirred with the chromium slag slurry according to the volume ratio of 0.5:1 to be left to stand for 1 day to obtain the chromium slag after the passivation treatment. According to the method, the chromium slag passivation pretreatment can berealized by adding the tr