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Nanofiltration Membrane + Reverse Osmosis Membrane Treatment of Nickel Plating Wastewater

Release Time:

2022-02-17 09:25

The method of plating nickel on metal or some non-metal surfaces by electrolytic or chemical methods is called nickel plating. Nickel plating includes electroless nickel plating and electroless nickel plating. Electroless nickel plating uses metal nickel as the anode, the cathode as the plated part, and the direct current as the current. A uniform and dense nickel coating is deposited on it. Bright nickel is obtained from baths with brighteners, while dark nickels are obtained from electrolytes without brighteners.

Electroplating wastewater is harmful to the environment. If nickel in wastewater is circulated into the biosphere through surface water or groundwater, it will accumulate in the human body, endanger human health, and even cause cancer. Various technologies have been developed in many countries to eliminate and reduce emissions. The traditional industrial treatment methods of electroplating wastewater have certain limitations. In recent years, membrane separation technology has developed rapidly. The separation process has the characteristics of no chemical reaction, no heating, no phase change, and no secondary pollution. Nickel has a wide range of applications in the electroplating industry. The plating solution mainly contains nickel sulfate or nickel chloride. Nickel and its compounds are toxic substances. In view of the increasingly strict environmental protection requirements and the characteristics of nickel plating wastewater, the following two membrane separation technologies are commonly used to treat electroplating wastewater.

1. Nanofiltration membrane treatment of nickel-plating wastewater

With the increase of operating pressure, the dynamic difference of the membrane separation process increases, the membrane flux increases, and the sewage treatment capacity increases. For nanofiltration membranes, when the membrane surface fouling rate is high, the rejection rate of Ni2+ decreases with the increase of pressure. Therefore, in the process of constant flow operation, when the operating pressure reaches a certain value, the membrane must be cleaned.

Under the same pressure, with the increase of the permeate flow rate, the retention rate of Ni2+ ions by the nanofiltration membrane also increases, and finally tends to be stable. At the same flow rate, with the increase of operating pressure, the retention rate of Ni2+ ions by nanofiltration membrane decreased. Under low pressure (0.5MPa), the removal rate of Ni2+ ions can reach more than 99%, and most of the heavy metal Ni2+ can be recovered. It can be seen that the nanofiltration membrane is more suitable for the treatment of wastewater containing Ni2+.

2. Reverse osmosis membrane treatment of nickel-plating wastewater

The change trend of membrane flux and operating pressure is similar to that of nanofiltration membrane treatment, that is, with the increase of operating pressure, the dynamic difference of the membrane separation process increases, the membrane flux also increases, the wastewater treatment capacity also increases, and the membrane flow rate increases. The increase in the amount of reverse osmosis is significantly smaller than that of nanofiltration.

Like nanofiltration, reverse osmosis has a high rejection rate of Ni2+ ions, which can reach more than 99% after stabilization. But unlike nanofiltration, reverse osmosis is less affected by operating pressure, and the retention rate is relatively stable. These two methods have good treatment effect on Ni2+-containing wastewater, but the operating pressure of reverse osmosis membrane is higher than that of nanofiltration membrane.

The nanofiltration membrane can be operated at a lower operating pressure, effectively saving energy consumption, and the recovery rate can reach more than 50%, which is not inferior to the same industry. The permeate can be recovered according to the specific requirements of customers, and the performance of membrane elements can be cleaned by recovery, reducing system operating costs. The system can be operated at room temperature without phase change, and will not cause adverse effects on the active ingredients in the material, and the output has a high content of active ingredients.

The reverse osmosis membrane has large water permeability, high desalination rate, stable water production, high cost performance, no phase change in the separation process, stable and reliable operation, and can effectively intercept organic matter, colloids, particles, bacteria, viruses, etc., and is resistant to pollution, easy to clean, Stable operation, low energy consumption, high water utilization rate, lower operating cost than other equipment, small volume of reverse osmosis membrane system, simple operation, easy maintenance, and strong practicability.

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