[China Aluminum Industry Net] aluminum surface treatment with large amounts of water, resulting in more waste water, hazardous waste materials continue to discharge. If not treated, it will pollute the environment. At the same time, China’s taxation on the amount of pollutants will also increase the cost and burden of enterprises. Therefore, considering the corporate social responsibility and benefits, wastewater treatment is necessary and necessary. The author summarizes the years of experience in process research and management of aluminum surface treatment and wastewater treatment, and proposes a practical and feasible wastewater treatment and reuse plan for peer reference.
1. Sources and types of surface treatment wastewater from aluminum profiles Surface treatment wastewater from aluminum profiles includes pre-treatment oil removal and after-acid water washing, alkaline water washing after alkaline corrosion, acidic water washing after acid etching, and acidity after oxidation. Washed water, colored acid containing Ni2+, Sn2+, acidic water, electrophoretic paint ion exchange equipment, waste acid, waste alkali and a small amount of electrophoretic paint wastewater. The wastewater is acidic after mixing and contains cations such as Al3+, Ni2+, Sn2+, Sn4+, Na+, Cr3+, and anions such as SO42-, F-, NO3-, Cl-, AlO2-, Ac-, surfactants and acrylic acid. Resins and other organic substances. The waste liquid contains waste sulfuric acid produced by degreasing and neutralization, waste sulfuric acid, waste sulfuric acid produced by oxidation, waste liquid produced by coloration, waste acrylic acid solution produced by electrophoretic paint, and waste liquid containing Ni2+, F-, etc. generated by sealing.
2. Methods for reducing the discharge of waste water and waste liquid The measures for reducing waste water and waste liquids include reasonable control of water control time and control of the loading angle to reduce the amount of tank liquid carried out, and try to adopt secondary three-stage countercurrent rinsing to reduce water consumption. After the etching and degreasing, the washed water is used for washing after alkali etching, and the washed water after oxidation is used for acid etching and washing after degreasing. In addition, in order to reduce or avoid the discharge of waste water and waste bath, various recovery devices should be designed and used in the production line, such as acid recovery, alkali recovery, anodization, aluminum RO, coloring RO recovery, electrophoretic coating RO Recovery devices that use these recovery devices can reduce the amount of waste water and waste liquid emissions to a large extent, while also greatly reducing the cost of production.
3. Principles and methods of aluminum surface treatment wastewater treatment Wastewater generated from surface treatment of aluminum profiles is mainly acid-alkali wastewater, containing small amounts of harmful anions and cations such as Ni2+, Sn2+, and F-. The treatment method is acid-base neutralization. Wastewater is generally acidic, and alkali must be added to neutralize the PH value to 7 ~ 8.5 or so. At the same time, in the neutralization process, cations such as Al3+, Ni2+, Sn2+, and Cr3+ form hydroxide precipitates. The neutralized and precipitated wastewater is pumped into the flocculation tank. At the same time, the dissolved polyamide flocculant is injected into the flocculation tank with a quantitative pump. After the flocculation, the wastewater enters the sedimentation tank. The sedimentation method includes inclined plate precipitation method and air flotation. Method, centrifugal precipitation, etc., I believe that the centrifugal precipitation method is relatively stable, after precipitation, the supernatant from the overflow overflow into the discharge tank or re-treatment reservoir. After the above-mentioned treatment of wastewater can be discharged, if you want to carry out wastewater reuse, this time the wastewater can be filtered into the RO device after treatment to remove excess anion and cations, organic matter, PH value may be low at this time , can be adjusted after the anion and cation exchange equipment to achieve reuse standards. The sludge produced by the sedimentation is periodically discharged into the sludge pool and processed into industrial waste residue after being processed by a plate-type cake pressing machine or a belt dehydrator and sent to the industrial waste residue treatment plant.
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