Wastewater treatment technology of aluminum profile surface treatment

At present, there are more than 600 aluminum profile production enterprises in China, which produce more than 2 million tons of aluminum profiles every year Meanwhile, they also discharge a large number of waste water, causing serious environmental pollution The water consumption of aluminum profile surface treatment is large, which produces a lot of waste water, and the harmful substances in the waste water are discharged continuously If not treated, it will pollute the environment At the same time, along with the tax on emissions, it will also increase the cost and burden of enterprises Therefore, it is necessary and necessary to carry out wastewater treatment from two aspects of corporate social responsibility and benefit The author summarizes many years of experience in the research and management of aluminum profile surface treatment and wastewater treatment process, and puts forward a set of feasible wastewater treatment and reuse scheme for reference 1 Source and type of waste water from aluminum profile surface treatment The waste water for aluminum profile surface treatment includes the pre-treatment oil removal and acid water after neutralization, alkaline water after alkali corrosion, acid water after acid corrosion, acid water after oxidation, colored water containing Ni2 +, SN2 +, acid water, waste acid, waste alkali and a small amount of electrophoretic paint waste water generated by ion exchange device for electrophoretic paint After mixing, the waste water is acid, containing cations such as Al3 +, Ni2 +, SN2 +, Sn4 +, Na +, Cr3 +, anions such as SO42 -, F -, NO3 -, Cl -, AlO2 -, AC -, surfactants and organic compounds such as propionic acid resin The waste liquid includes waste sulfuric acid produced by degreasing and neutralization, waste nitric acid, waste sulfuric acid produced by oxidation, waste liquid produced by coloring, waste acrylic acid produced by electrophoretic coating, and waste liquid containing Ni2 +, F - produced by hole sealing 2 The methods to reduce the discharge of waste water and liquid waste are to reasonably control the water control time and the loading angle to reduce the volume of tank liquid, and try to use two-stage and three-stage countercurrent rinsing to reduce the water consumption The washing water after acid etching and degreasing is used for washing after alkali etching, and the washing water after oxidation is used for washing after acid etching and degreasing In addition, in order to reduce or avoid the discharge of waste water and waste tank liquid, the production line should design and use various recovery devices, such as acid recovery device, alkali recovery device, anodizing dealumination device, coloring liquid ro recovery device, electrophoresis painting ro recovery device The use of these recovery devices can reduce the amount of waste water and waste liquid discharge to the maximum, and at the same time minimize the amount of waste water production costs 3 Principle and method of waste water treatment for aluminum profile surface treatment The waste water from aluminum profile surface treatment is mainly acid-base waste water, containing a small amount of harmful anion and anion such as Ni2 +, SN2 +, F -, etc the treatment method is acid-base neutralization Generally, the waste water is acid and needs to be neutralized by adding alkali, and the pH value should be adjusted to about 7-8.5 At the same time, in the neutralization process, the cations Al3 +, Ni2 +, SN2 +, Cr3 + and so on all form hydroxide precipitation After neutralization and sedimentation, the waste water is pumped into the coagulation tank, while the dissolved polyamide flocculant and waste water are pumped into the coagulation tank by a quantitative pump After coagulation, the waste water enters the sedimentation tank The sedimentation methods include inclined plate sedimentation, air flotation, centrifugal sedimentation, etc the author thinks that the centrifugal sedimentation method is more stable After sedimentation, the clear liquid overflows from the upper overflow port and enters the discharge tank or Reprocessing reservoir After the above treatment, the waste water can be discharged up to the standard If the waste water is to be reused, the waste water at this time can be put into RO device after coarse filtration for treatment to remove the excess anion and organic matters At this time, the pH value of the water may be low, and it can be reused up to the standard after the anion exchange device adjustment The sludge produced by sedimentation is regularly discharged into the sludge tank, which is treated by plate type cake press or belt type dehydrator, and then becomes industrial waste, and is sent to the industrial waste treatment plant Source: chinalco.com“