What causes wastewater to turn yellow after treatment?
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The wastewater from our factory is mainly electroplating wastewater, which contains copper. After copper is displaced by iron, this wastewater is sent to the wastewater tank. Calcium hydroxide is used in the treatment process, and the sedimentation effect in the sedimentation tank is quite good! However, after the wastewater treatment stops and for some time after that, the color of the wastewater in the sedimentation tank becomes abnormal. What is the reason? How to prevent it from turning yellow? I need expert advice! Thank you!
It is mainly due to the presence of iron; adding calcium hydroxide can neutralize part of it, forming iron hydroxide. Since the amount is small, the color is yellow rather than red
In my opinion, the cause of the floc formation is iron hydroxide colloid, with the electrochemical formula Fe(OH)3; it appears as a brown or reddish-brown powder or as dark brown flocculent precipitates.
Due to the addition of ferrous flocculants in the pre-treatment stage, although most of it was precipitated by adding lime, there was still an excess of ferrous ions overall. After staying in the sedimentation tank for some time, these ions reacted with oxygen in the air to form trivalent iron ions, which appear orange-yellow at low concentrations. The only option is to control the amount of ferrous ion used in the preceding stage and gradually reduce it, thereby decreasing the excess amount.
The specific reason should be considered in relation to the device; phenol will appear
I don’t know how your family came up with such a bad idea – what’s the point of adding calcium hydroxide to precipitate iron? As for wastewater treatment, calcium ions are also present in it; however, this is better than having iron ions. Perhaps calcium hydroxide is cheap, but the precipitated iron hydroxide isn’t very useful either. The priorities are reversed. I suggest you install an ion removal device – it’s not in your own interest to harm others! ^_^
The reason is iron ions in the water
The original poster said that iron is used to replace copper in water; how do you interpret this as the use of ferrous salts for flocculation? Is it possible that it is a direct substitution reaction between metal ions? If we understand it in terms of the function of flocculants, since copper ions have been flocculated into sludge and settled, there is no need to add lime for precipitation anymore. Other views agree. I hope to communicate with you.
It is the color of ferric iron, resulting from the hydrolysis of the Fe(OH)3 flocs formed
It might be due to iron, as a result of oxidation
Trivalent iron ions are formed, which appear orange-yellow at low concentrations.