金属铬络合染料废水中的铬Cr(Ⅲ)与偶氮类有机配体结合,呈络合状态,结构非常稳定。采用常规的中和混凝法对黑色、黄色和橙色三种铬络合物的废水进行处理,均不能有效地去除铬。研究表明,温度和酸度是影响络合态铬离子热力学稳定性的主要因素。对于黄色或橙色铬络合物,将废水进行预热以提高处理温度,或加酸酸化,都会使络合态铬离子结构破坏;而对于黑色铬络合物,其结构更为稳定,必须酸化并同时提高处理温度,才能有效地破坏黑色铬络合物的结构,游离出的铬离子极易通过投加石灰乳中和沉淀去除。因此,通过酸化、预热、中和混凝等步骤,可将该类高浓度络合态铬离子完全解离并去除,处理后含铬质量浓度降至1.0mg/L以下,达到了重金属处理排放要求。

Trivalent chromium existing in wastewater from the dye plants is in complex state and its structure is very stable when coordinated with organic azo compound ligands. The conventional methods，such as neutralization-flocculation are not very effective for removing the Cr-complexes in three kinds of wastewater; black，yellow and orange wastewater. The results show that temperature and acidity are the two main factors influencing the thermodynamics stability of the complex chromium ion. For yellow or orange chromium complex，their structure could be destroyed by means of heating the wastewater raise its temperature or acidification. But for black chromium complex，its structure is more stable，it must be heated to higher temperature and be acidified simultaneously. The structure of black chromium complex could be destroyed efficiently. Complex chromium ion could be dissociated，and the free chromiumion could be removed easily via neutralization and precipitation in case of lime emulsion. Therefore，by means of such procedures as acidification，preheating, neutralization and flocculation，these complex chromium ions at high concentration can be destroyed and removed completely. The chromium content in the wastewater is lower than 1.0 mg/L after treatment，can meet the demand of heavy metal dischargestandard.