The industries mainly involved in heavy metal pollution include mining, chemical industry, printing and dyeing, electroplating and other industries. These industries will discharge a large amount of heavy metal elements such as lead, mercury, nickel, chromium, arsenic, etc. in the process of production. Wastewater containing heavy metals will cause harm to the environment. Serious pollution.
The absorption of these substances by plants and aquatic organisms will form an enrichment effect, affecting other organisms through the relationship of the food chain, causing metabolic disorders in animals and protein inactivation, which has caused serious harm to human health.
Main technologies for heavy metal wastewater treatment
1.1 Method of chemical precipitation
The chemical precipitation method is widely used. This method is mainly to add specific chemical substances, such as sulfides, hydroxides and other precipitants to the heavy metal wastewater. These substances chemically react with heavy metal ions to form precipitation substances to remove heavy metal elements in the water. .
The operation process of chemical precipitation method is relatively simple. The main disadvantage is that a certain amount of precipitation waste will be formed during the treatment process. These substances need to be treated again. If the treatment method is improper, it will cause secondary pollution.
In recent years, with the continuous progress of science and technology, the chemical sedimentation method has been significantly improved in the process of operation. Some new precipitants have been widely used, which has improved the removal rate of heavy metal ions, and the treatment level of waste residue has also improved. Significantly improved, which also makes the application of this technology more extensive.
1.2 Electrolysis
The electrolysis method is mainly to add electrodes to the wastewater. Through the action of direct current, the positively charged heavy metal ions will move to the cathode, and become metals that can be adsorbed on the electrode surface or precipitated through reduction. Effective treatment can also remove salt from water.
The electrolysis method does not require additional chemical reagents in the process of treating wastewater, and will not cause secondary pollutants. The main disadvantage is that with the continuous progress of the electrode reaction, heavy metal ions are continuously absorbed, making the resistance value of the electrode continuously This also increases the power consumption used, so this method is not suitable for the treatment of heavy metal wastewater with relatively low concentrations.
1.3 Biosorption method
The method of biological adsorption is a new method of heavy metal wastewater treatment. This method uses covalent and electrostatic effects to adsorb heavy metal elements on the surface of organisms through the analysis of bioadsorption characteristics, so as to achieve the effect of heavy metal treatment.
In the specific implementation process, firstly, the functional groups and macromolecular substances on the surface of biological cells are adsorbed with heavy metal ions, and then the biological cells transport some heavy metals, so as to achieve the effect of reducing the content of heavy metals. This method has been widely used in many enterprises. For example, a lead-zinc mine in Hunan uses Bacillus licheniformis isolated from ore to absorb heavy metal ions in wastewater. The detection effect is very obvious. same
At the same time, the company also used Stenotrophomonas maltophilia to treat the chromium element in wastewater, which also achieved good results. pregnancy
The adsorption of heavy metals in wastewater is mainly suitable for use in wastewater with relatively low concentrations of heavy metals, which can effectively resist the interference of other factors in the environment. In the process of use, it is necessary to reasonably control the biological efflux used to avoid heavy metal elements. enrichment and food chain transmission. In general, the application prospect of this technology is relatively broad.
1.4 Ion exchange method
The treatment of heavy metal wastewater by ion exchange method is mainly through the use of exchangers to exchange heavy metal ions. In the process of heavy metal wastewater passing through the exchanger, the ion concentration has a certain difference. The functional groups of the exchanger can promote the ion exchange process, so as to achieve Removal of heavy metal ions.
At present, the commonly used ion exchangers include zeolite, anion and cation exchange resins, bentonite, etc. Anion and cation exchange resins have the widest application range. In addition to removing different types of heavy metal ions, this exchanger can also effectively separate ions. .
At the same time, modern technology has added fluidization technology to the fixed bed of the ion exchange method, which also makes the ion exchange technology more widely used.
1.5 Membrane separation method
The main principle of the membrane separation method is to use a semi-permeable membrane made of special materials to separate heavy metal ions. This method will not change the overall chemical and molecular morphology of the solution, and has the main characteristics of energy saving, environmental protection and high efficiency.
The recovery of heavy metal elements can be imagined by using the membrane separation method, which has a wide range of applications.
At present, the membrane separation methods commonly used by enterprises include ultra-microfiltration, reverse osmosis, nanofiltration, etc. With the continuous advancement of technology, new treatment membrane materials are gradually applied, which also improves the treatment effect. Many enterprises use this method to achieve Zero discharge of heavy metals.
Resource utilization of heavy metal wastewater treatment
Heavy metal wastewater treatment requires not only the discharge of heavy metals to meet the standards, but also the recycling of wastewater and heavy metals to realize the reuse of heavy metals and water resources. Relevant enterprises have also achieved certain results in the recycling of heavy metal wastewater treatment.
An enterprise in Guangdong Province uses membrane treatment technology and chemical sedimentation technology to treat the wastewater generated from battery production.
First, a certain amount of sodium hydroxide and limestone were added to the wastewater to control the pH value, the heavy metal ions were separated from the wastewater by a precipitant, and the heavy metal precipitation was separated by the membrane treatment technology.
After the above treatment, the concentration of heavy metals in wastewater is significantly reduced, and the recovery rate of heavy metals is significantly improved, which meets the relevant requirements of daily production and environmental protection of enterprises.
Conclusion
The harm of heavy metal elements to the ecological environment is relatively serious, and relevant enterprises need to actively do a good job in the treatment of heavy metal wastewater. Make due contributions to environmental protection.