Treatment of Copper Ion in Industrial Wastewater
Copper plating layer is often used as the bottom layer of nickel plating, tin plating, chrome plating, silver plating and gold plating to improve the bonding strength between the base metal and the surface coating and anticorrosive property of the coating. Therefore, the electroplating wastewater containing copper is very common in electroplating industry, And the wastewater usually contains a variety of heavy metals and complexing agent. At present, the treatment of copper-containing electroplating wastewater mainly by chemical, ion exchange, membrane separation, adsorption, biological and so on.
1 chemical treatment of copper-containing electroplating wastewater
1) and precipitation method
At present, chemical neutralization and coagulation sedimentation are often used to treat copper-containing electroplating wastewater. While neutralizing the acid and alkali in the wastewater, the copper ions form copper hydroxide precipitate, which is then removed by the solid-liquid separation device Precipitate.
A single copper wastewater at pH 6.92, the copper ions can be removed to achieve the standard precipitation, the general electroplating wastewater in the coexistence of copper and iron, the control pH value of 8 to 9, can also meet the emission standards. However, for the mixed electroplating wastewater containing copper and other heavy metals and complexes, the removal efficiency of copper is not good, and the discharge standard is not up to the standard, mainly because the treatment is to regulate the pH value of wastewater, If the wastewater contains cyanide, ammonium and other complex ions, and copper ions to form complexes, copper ions are not easy to dissociation, making the copper ion can not meet the standard discharge. (2) the pH value of the best precipitation, making the removal effect is not good; Especially for cyanide containing copper mixed wastewater treatment, the concentration of copper ions and CN- concentration is almost proportional to, as long as the wastewater CN-exist, the concentration of copper ions in the effluent will not be achieved. This makes the use of neutralization precipitation treatment of copper mixed wastewater effluent effect is not good, especially for the removal of copper is not good.
2) sulfide precipitation method
Sulfide precipitation has great advantages in treating wastewater containing copper, which can solve the problem that some weakly complexed heavy metals are not up to standard. The solubility of copper sulfide is much lower than that of copper hydroxide, and the pH range of reaction is wide, The sulfide also precipitates a portion of the copper ion complex, so no shunting is required. However, due to the small sedimentation of sulfides, it is difficult to settle, limiting its application. In addition, the presence of cyanide ions affects the precipitation of sulfides, which will dissolve some of the sulfide precipitates.
3) electrochemical method
The electrochemical treatment of copper-containing wastewater has the advantages of high efficiency, automatic control and low sludge volume. The treatment of copper-containing electroplating wastewater can directly recover the metal copper, and the treatment has wider adaptability to the concentration range of copper, High (copper mass concentration greater than 1g / L) of the waste water has some economic benefits, but the low concentration of current efficiency is low.
2 Ion Exchange Process for Copper Electroplating Wastewater
Ion exchange is one of the main methods to treat copper-containing wastewater. And a variety of ion exchange agents continue to introduce new. There are many types of ion exchangers. The effect of complexing agent on copper - containing electroplating wastewater is little.
1) ion exchange resin
Ion exchange resin in addition to copper is quite good, resin treatment containing high concentrations of ammonia copper rinse has been reported; there are factories using weak acid cation exchange resin treatment of acid sulfate copper rinse wastewater; some companies with strong alkaline anion exchange resin Pyrophosphate copper plating wastewater, so that part of the water recycling. Another chelate resin has good selectivity, adsorption capacity, fast and so on, and the exchange rate. However, because these chelating resins are expensive, they mostly remain in the experimental stage and are less widely used in industry.
2) ion exchange fibers
Ion exchange fiber is a kind of new ion exchange material with rapid development in recent years, and also has a great development in the field of heavy metal waste water treatment. The adsorption of Cu on the electroplating wastewater by modified polyacrylonitrile fiber shows that the content of copper ions in the electroplating waste water is obviously lower than the national emission standard after it is adsorbed by modified polyacrylonitrile fiber.
3 Membrane Separation Technology for Copper Electroplating Wastewater
Membrane treatment of industrial wastewater generally use reverse osmosis, ultrafiltration and combination of the two technologies, membrane treatment of industrial wastewater is the key to select the appropriate membrane separation conditions. The use of reverse osmosis membrane separation technology for the treatment of copper-containing electroplating wastewater has been reported a lot, the method of copper complexes of electroplating wastewater treatment effect is also good, and some have been used in industry, and other water treatment technology used to obtain very Good results.
4 Adsorption Process for Copper Electroplating Wastewater
The treatment of copper-containing wastewater by adsorption has many advantages. It has become the focus of water treatment research. Many good adsorbents have been developed, especially industrial wastes and crop residues as adsorbents, and the modification of existing adsorbents is improved. Its adsorption performance. Zeolite and Maifanite are cheap and widely used, and the adsorption of Cu2 + on Maifanshi can reach more than 95%. Kyanite can reach 100% adsorption effect on copper ions under appropriate conditions; such as coal ash and slag Can be used as an adsorbent to treat copper-containing electroplating wastewater, and the synthesis of zeolite 4A from coal ash can adsorb many kinds of heavy metals, and the adsorption effect on copper ions is very good.
At present, the research on the adsorption of copper and cadmium in plant and animal waste has been carried out. In order to increase the adsorption capacity and adsorption selectivity, the modified adsorbent can improve the adsorption of copper ions. The chitin modified by tartaric acid greatly improved the adsorption of copper ions, and the capacity of copper ions adsorbed by chicken feathers after alkali treatment was greatly improved, and the adsorption effect was very good. The adsorption of copper ions in the mixed electroplating wastewater by sawdust is superior to the treatment of copper in single wastewater.
5 biological treatment of copper electroplating wastewater
Biological treatment of copper-containing wastewater is characterized by the largest in the process of running microorganisms can continue to proliferate, the amount of biomass removal of copper ions increased with the increase in biological mass. The biological method has many advantages, such as comprehensive treatment ability, so that the harmful metals such as copper, hexavalent chromium, nickel, zinc, lead, lead and other harmful metal ions can be effectively removed in the wastewater treatment method; the process method is simple and practical; ; Less sludge, secondary pollution was significantly reduced. However, the biological treatment of copper-containing wastewater there are functional bacteria breeding speed and the reaction rate is slow, the treatment of water is difficult to reuse shortcomings.