Recycling And Harmless Treatment Of Chromium Residue

The soluble hexavalent chromium in the huge number of chromium residueproduced by the chromium salt industry has posed a serious danger to the healthand living environment of human for its highly toxic．With a large amount untreatedand rapidly growing of new chromium residue，it is the major problem how to treatit．There are many problems existing in the disposal technology of dealing withchromium slag such as low treatment efficiency， high cost but not treatedthoroughly to be solved．The chromium residue has been the key point to restrictthe development of chromium salts industrial and the growth of national economic．Compared to the current processes，a process has been put forward in thispaper． To begin with strengthening the hexavalent chromium eatraction fromchromium residue and adopting wet harmless prosess to treat the leachingchromium residue，followed by recycling chromium from the leaching solutionand adsorbing the hexavalent chromium in the residual solution with self-madeactivated carbon．It achieves the goal that making sure the recycling of valuableproduct and the chromium residue and effluent discharged up to the standard．In the experiments of intensified leaching and harmless treatment of chromiumresidue， we focus on the intensified leaching of hexavalent chromium fromchromium residue，firstly．The result shows that by using Na2SO4-Na2CO3solutionwith a liquid-solid10:1as leaching agent and CH3(CH2)11SO3Na（0.001g）as anadditive to leach chromium residue in a stirring intensity of300r/min for2h andrepeat it5times，it can obtain a leaching rate of94.51%，achieving the goal ofstrengthening hexavalent chromium eatraction from chromium residue．Then，inorder to treat the leaching chromium residue with a hexavalent chromiumconcentration of30.14mg/L，the harmless effect of complex reagent treating theleaching chromium residue is studied．The result shows that by using a complexreagent of0.20ml RNF-261（8%）and0.2ml NaHSO3（0.1mol/L）as reductant andCH3(CH2)11SO3Na（0.001g）as an additive to treat5g leaching chromium residue ata humidity of50%and at a temperature of60℃in a closed reaction for30min，it can obtain treated leaching chromium residue with hexavalent chromium leachingconcentration of0.14mg/L，which is lower than the value of5mg/L specified in（GB5085.3-2007），achieving the goal of harmless treatment of chromiumresidue．In the experiments of recycling chromium from chromium residue leachingsolution and the residual solution treatment of meeting the requires of industryproduce，we focus on the recycling of chromium from the chromium residueleaching solution with a hexavalent chromium concentration of201.45mg/L．Theresult shows that using a complex reagent of0.30ml RNF-261and0.2mlCH3CH2OH as reductant to treat100ml chromium residue leaching solution for60min at pH value of9，it can obtain61.65mg precipitation in the forms ofCr(OH)3·H2O and its purity is98%when dried． Then，in order to treat the residualsolution with a hexavalent chromium concentration of10.14mg/L，the adsorptionperformance of self-made activated carbon to the hexavalent chromium in theresidual solution is studied．The result shows that using0.03g self-made activatedcarbon as adsorbent to absorb hexavalent chromium at a temperature of20°C and atpH value of6in the presence of ultrasound of55%for20min，it can obtain treatedresidual solution with hexavalent chromium concentration of0.34mg/L，which islower than the value of0.5mg/L specified in （GB8978-1996），achieving the goalof harmless treatment of residual solution．...