Treatment of zinc-nickel alloy wastewater
Five major pain points
Zinc-nickel alloy wastewater is one of the most difficult to treat electroplating wastewaters. Usually, in the production process of electroplating and surface treatment industries, wastewater containing heavy metals such as zinc, nickel, and lead is generated. Zinc-nickel alloy wastewater mainly contains harmful substances such as nickel, zinc, ammonia nitrogen, COD, etc. It has complex components and many complexes. Therefore, to treat this kind of wastewater, the complexing agent must be removed first, otherwise the heavy metal ions cannot be precipitated. When treating zinc-nickel alloy wastewater, there are mainly the following pain points:
1. Difficulty in removing heavy metals: The concentration of zinc and nickel ions is high and the complex state is stable. The traditional chemical precipitation method is inefficient and requires precise control of pH or special agents;
2. Complexing agent interference: Strong complexing agents such as organic amines and citric acid encapsulate metal ions, and conventional oxidation and complexing (such as Fenton) are difficult to completely decompose;
3. Complex process and high cost: Multi-stage treatment (pretreatment + main treatment + deep treatment) is required, and the investment and operation and maintenance costs of technical equipment such as membrane separation and evaporation crystallization are high;
4. Secondary pollution risk: Chemical agent residues and improper sludge disposal are prone to environmental problems;
5. Poor stability: Production instability leads to changes in wastewater discharge, affecting the stability of the treatment system.
Five zinc-nickel alloy treatment processes commonly used in the market
1. Chemical precipitation method: suitable for large-scale wastewater treatment, with high removal rate for free metal ions, but unable to directly treat complex heavy metals, requiring pre-decomposition (such as Fenton oxidation); large sludge output, prone to secondary pollution; nickel ion residues are prone to exceed the standard (need to be combined with coagulant strengthening).
2. Electrolytic deposition method: recyclable metal resources (such as nickel plates), suitable for high-concentration wastewater; no chemical agent consumption, good environmental protection; high energy consumption, large equipment investment; low efficiency for low-concentration wastewater, easy passivation of electrodes; unable to treat complex metals.
3. Ion exchange/chelate resin method: high selectivity, deep removal of low-concentration heavy metals (such as Ni²⁺≤0.05mg/L); resin is regenerable, long-term use cost is controllable; resin is easily contaminated by organic matter, requiring frequent regeneration; high initial investment, not suitable for high-salt wastewater;requires pretreatment to remove suspended matter.
4. Membrane separation technology (reverse osmosis/nanofiltration): excellent effluent quality, reusable; no phase change, good energy saving; serious membrane pollution, high maintenance cost; concentrated liquid requires secondary treatment (such as evaporation and crystallization); high investment and operating costs.
5. Advanced oxidation technology (Fenton/ozone): strong ability to break plexus, can degrade organic pollutants; combined with precipitation method can improve heavy metal removal rate; high reagent cost (such as H₂O₂, O₃); produces iron-containing sludge, which is difficult to dispose; harsh reaction conditions (pH needs to be precisely controlled).
New process for zinc-nickel alloy wastewater treatment
The largest surface treatment circular economy industrial park case in China
In order to completely solve the pain point of zinc-nickel alloy wastewater treatment, Winsonda can effectively break plexus of zinc-nickel alloy wastewater through the existing low-temperature evaporation concentration + low-temperature evaporation crystallization combined process, and wastewater concentration + crystallization can be used in a two-pronged approach to make the overall device operate stably for a long period of time. Practice has shown that the combined process of “low-temperature cleavage-vacuum evaporation-crystallization separation” is an ideal new process for zinc-nickel alloy wastewater treatment, which can effectively solve the pain points of high salt degradation and poor stability in zinc-nickel alloy wastewater treatment, and is especially suitable for medium and large electroplating parks with an annual water output of >1,000 tons.
Taking a certain electroplating industrial park in Jiangsu as an example, the customer, as the largest surface treatment circular economy industrial park construction operator in China, originally adopted the dosing + physical and chemical treatment process, with poor system stability and low treatment load. In December 2023, the customer introduced Winsonda’s “low-temperature heat pump evaporation system (LT-20T, daily processing capacity 20 tons) + low-temperature evaporation crystallization drying system (LT-ZQ-500, daily processing capacity 10 tons)” to treat the zinc-nickel alloy wastewater in combination. Through technical optimization, the overall treatment process was shortened, the terminal drainage indicators were guaranteed, and it has been running stably to date.
Before operation: nickel content of distilled water: 3g/L
After operation: nickel content of distilled water:<0.1ppm, water content of concentrate: ≤18%
As the first domestic use of the “low-temperature heat pump evaporation + low-temperature evaporation crystallization drying” combined process to solve the problem of zinc-nickel alloy wastewater disposal, Winsonda has solved the pain point of unstable traditional physical and chemical disposal effects. It can treat 6,000 tons of zinc-nickel alloy wastewater for customers every year, with stable and up-to-standard effects, setting a new environmental protection benchmark for the industry; the treated wastewater can be reused in the front-end production link to improve the utilization rate of water resources and reduce the water cost of enterprises. Help enterprises transform and upgrade and promote green and sustainable development.
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