The wastewater and rinsing water discharged from various metal products during mechanical machining contain various metal ions, which are highly toxic. Wastewater pollution from mechanical machining is extensive and significant, making it one of the key industrial wastewater streams. So, what are the methods for treating heavy metal wastewater in mechanical machining? Let's take a look together!
Sources
Heavy metal wastewater in mechanical machining generally contains heavy metals such as cadmium, chromium, lead, nickel, zinc, and mercury. Acidic wastewater and waste solutions mainly come from material pickling workshops in factories.
Hazards
Heavy metals are not biodegradable but can accumulate thousands of times through bioaccumulation in the food chain, eventually entering the human body. Heavy metals strongly interact with proteins and enzymes in the human body, causing them to lose their activity. They may also accumulate in certain organs, leading to chronic poisoning.
Common Methods for Treating Heavy Metal Wastewater:
Electrolysis Method
This method is widely used for treating heavy metal wastewater containing cyanide. Electrolytic oxidation is employed to decompose cyanide and convert heavy metals into hydroxide precipitates for removal from wastewater. Electrolysis is also effective in the efficient recovery of pure mercury or mercury compounds from mercury sulfide residues.
Ion Exchange Method
Since heavy metals in wastewater mostly exist in ionic form, the ion exchange method is effective in removing and recovering heavy metals from wastewater.
Biological Treatment Method
Biological treatment methods utilize the coagulation, absorption, accumulation, and enrichment effects of microorganisms or plants to remove heavy metals from wastewater. This includes methods such as bioremediation, biological flocculation, and microbial metabolism.
Chemical Method
The addition of a heavy metal chelating agent, such as RS200, is used in the chemical method. The chelating agent chelates heavy metal ions through various chelating groups, forming hydrophobic structures and precipitates. Additionally, with the action of high-molecular-weight polymers, the precipitation speed and removal efficiency are significantly improved through aggregation and net trapping, overcoming the limitations of linear chelation precipitation.
The heavy metal chelating agent RS200 is widely used in fields such as electroplating, PCB manufacturing, mining, non-ferrous metal smelting, and chemical product purification (heavy metals). It is particularly effective in removing complexed heavy metals that cannot be treated by conventional methods (such as caustic soda + PAC + PAM). It has shown excellent results in removing complexed copper and complexed nickel from PCB and FPC wastewater. It is widely applied in the treatment of chemical nickel, aluminum anodizing wastewater, and zinc-nickel alloy wastewater. It can stably meet the standards specified in Table III (Cu < 0.3mg/L, Ni < 0.1mg/L).