How to remove heavy metals in sludge and what methods should be used to remove heavy metals in waste

There are three main methods: physics, chemistry, biology, etc.

Physical remediation methods mainly include masking method, engineering removal, heat treatment method, etc.

The principle of chemical remediation method is that the chemical agent reacts with the pollutant such as oxidation, reduction, precipitation, polymerization, etc., so that the pollutant is separated from the sediment, degraded and converted into a low-toxic or non-toxic chemical form. Chemical remediation mainly includes chemical fixation, chemical leaching, and electric repair.

The biological method is a comprehensive use of modern biotechnology to remove harmful pollutants in the soil and improve the soil quality, mainly including phytoremediation, microbial remediation, animal remediation, and joint remediation.

Phytoremediation is mainly composed of four parts: plant stabilization, plant extraction, plant volatilization, and plant root filtration.

The microbial remediation of heavy metal contaminated soil mainly includes two aspects, bioadsorption and bioredox.

Some data show that citric acid can remove heavy metals in sludge, but it is not practical to apply it in engineering.

Sludge aerobic composting has a certain passivation effect on heavy metals, and the combination of heavy metals in the reaction process can reduce the activity of heavy metals such as Zn, Cu, Pb, Mn and other heavy metals in sludge, and reduce the risk of heavy metal pollution in sludge in land use.

This question is not very clear.

Generally speaking, when the sewage contains heavy metals, it is necessary to do everything possible to think about it to settle into the sludge, and then dewater as much sewage with high water content as possible through pressing and other methods, and finally the sludge containing heavy metals is incinerated and buried for final treatment.

Private messages. Air flotation method Air flotation method is a method of solid-liquid separation by using the adsorption of air bubbles, adding a fluttering agent with the opposite charge to the heavy metal-containing wastewater to generate complexes or precipitates, so that they attach to the bubbles to form scum and remove. The air flotation method has unique advantages for the treatment of electroplating wastewater, especially when the concentration is low: the equipment is simple, the area is small, it is suitable for intermittent operation, and the operating cost is not high, but the salt and grease content of the effluent is high, and the problem of scum and purified water reuse needs to be solved.

ElectrolysisElectrolysis is a method to eliminate the toxicity of heavy metals by electrochemical interaction between electrodes and heavy metal ions. This method makes the heavy metal ions in the wastewater oxidize and reduce the reaction on the ano-cathode respectively through the electrolysis process to enrich the heavy metals, and then carry out treatment, this method removes heavy metals with the advantages of simple equipment, small occupation and easy operation, but the energy consumption is high and the treated water volume is small.

At present, the methods for removing heavy metals in wastewater mainly include chemical methods, physicochemical methods and biological methods, including chemical precipitation, electrolysis, ion exchange, membrane separation, activated carbon and silica gel adsorption, biological flocculation, biological adsorption, plant remediation and other methods. The use of chemical and physicochemical methods will transfer residual pollution, which is easy to cause secondary pollution, and it is difficult to deal with harmful heavy metal pollution in large watersheds and low concentrations.

Among them, the multi-use chemical method and biological flocculation method have the longest use time and the widest range; The biological method has attracted more and more attention due to its advantages of good effect, low investment and low operating cost, easy management and operation, and no secondary pollution.

1 Chemical method The chemical method mainly includes chemical precipitation method and electrolysis method, which is mainly suitable for the treatment of wastewater containing high concentration of heavy metal ions.

2 Physicochemical method Ion exchange method and membrane separation technology are suitable for the treatment of wastewater containing low concentrations of heavy metal ions.

3 Biological law.

Biological flocculation methodBiological flocculation is a decontamination method that uses microorganisms or metabolites produced by microorganisms to carry out flocculation and precipitation.

Bioadsorption Bioadsorption is a general understanding of the adsorption of heavy metal ions by microbial cells through a series of biochemical actions, including complexation, chelation, ion exchange, adsorption, etc.

Plant remediation technology The absorption and enrichment mechanism of heavy metals by plants is mainly in two aspects: one is to use the absorption and filtration of heavy metal wastewater by the developed root system of plants to achieve the enrichment and accumulation of heavy metals. The second is to use the activity principle of microorganisms and the affinity between heavy metals and microorganisms to convert heavy metals into products with lower toxicity.

By harvesting or removing the branches of plants that have accumulated and enriched heavy metals, the concentration of heavy metals in the soil or water body is reduced, so as to achieve the purpose of pollution control and environmental restoration.

Wastewater with high content of heavy metal ions is generally treated by chemical and physical methods.

1. Chemical precipitation method: its principle is to transform the dissolved heavy metals in wastewater into water-insoluble heavy metal compounds through chemical reactions, and remove the precipitate from the aqueous solution through filtration and separation, including neutralization precipitation method, sulfide precipitation method, and ferrite co-precipitation method. Due to the influence of precipitant and environmental conditions, the concentration of effluent from the precipitation method often does not meet the requirements, and further treatment is required, and the resulting precipitate must be well treated and disposed of, otherwise it will cause secondary pollution.

Heavy metal traps in chemical agents are also a good choice.

2. Electrolysis method: It is to use the electrochemical properties of metals, metal ions can be separated from relatively high concentration solutions during electrolysis, and then utilized. The electrolysis method is mainly used for the treatment of electroplating wastewater, and the disadvantage of this method is that the concentration of heavy metal ions in the water cannot be reduced very low.

Therefore, the electrolysis method is not suitable for the treatment of wastewater containing heavy metal ions at lower concentrations.

At present, there are two main methods of sludge heavy metal treatment: stabilization and removal.

1. Stability of sludge heavy metals.

Add some passivating agents, such as quicklime, fly ash and clay, to increase the pH. The heavy metals are converted into hydroxides and other precipitates to passivate the heavy metals and kill pathogenic bacteria.

2. Removal of heavy metals in sludge.

1) Adsorption method.

Substances with special structures or chemical compositions are used to separate and remove heavy metals (e.g., natural zeolite);

2) Chemical leaching method.

Sulfuric acid, hydrochloric acid or nitric acid are used to reduce the acidity of the sludge, and the insoluble metal compounds form dissolved metal ions through dissolution; or use EDTA, citric acid and other complexing agents to separate the heavy metals in them through ion exchange, acidification, chelating agent and surfactant, so as to reduce the total amount of heavy metals in sludge;

3) Electric repair method.

Electric technology was first applied in the removal of heavy metals in soil in the 80s of the 20th century, and the application of heavy metal removal in urban sludge has just started.

4) Biological leaching method.

Biological leaching technology is a technology that uses microorganisms in nature to produce oxidation, reduction, complexation or dissolution through direct action or indirect action of other metabolites, and separates and leachs some insoluble components in the solid phase, such as heavy metals, among which the most widely used are Thiobacillus ferrous oxide and Thiobacterium oxide.

If the EIA is clearly stated, it is best to consult the environmental protection bureau if it is not clear.

Common treatment bai:

1: Drying, incineration, and fly ash generated after incineration will be sent to the hazardous DAO waste treatment center for solidification treatment;

2: Inside the water. Mud plant synergy.

To deal with sludge (hazardous waste), Huaxin Cement in Hubei Province has embarked on a project to co-dispose of hazardous waste, because the cement kiln can solidify heavy metals in the crystal lattice during the production process. However, the fly ash at the end of the kiln still needs to be treated as hazardous waste and solidified.

(1) Chemical precipitation method: chemical precipitation method is a method to transform the dissolved heavy metals in heavy metal wastewater into water-insoluble heavy metal compounds, including neutralization and precipitation and sulfide precipitation methods, most of which are treated by heavy metal scavenger HMC-M1.

2) Redox treatment: The CR in the electroplating wastewater mainly exists in the form of Cr6 ions, so after adding a reducing agent to the wastewater to reduce the Cr6 to the slightly toxic Cr3, add lime or NaOH to produce Cr(OH)3 precipitation and separation.

3) Solvent extraction: Separation solvent extraction is a commonly used method for separating and purifying substances. Due to the contact between liquid and liquid, it can be continuously manipulated, and the separation effect is better.

When using this method, it is necessary to choose an extractant with high selectivity, and the heavy metals in the wastewater generally exist in the form of cations or anions, such as under acidic conditions, complexing reaction with the extractant, extracting from the aqueous phase to the organic phase, and then being retraced to the aqueous phase under alkaline conditions, so that the solvent can be regenerated for recycling.

Heavy metal pollution is a common tap water pollution, the main common heavy metal pollution is lead, zinc, nickel, cobalt, chromium, mercury, cadmium, excessive heavy metals once into the human body will seriously affect health. Let's take a look at how to clean heavy metal pollution:

Adsorption cleaning method: The principle is mainly to adsorb heavy metals in water through materials with pores on the surface and strong adsorption force, such as activated carbon, minerals and molecular sieves, which can be used as materials for adsorption method. Activated carbon is the earliest and most widely used adsorbent, but it is expensive and has a short service life.

The use of adsorption method to remove heavy metals can only remove most of the heavy metals in the water, but cannot be completely removed.

The use of water purifier filtration to remove heavy metals in water is the most widely used method to remove heavy metals from tap water, and it is also the best way to remove heavy metals from water. Its principle is to remove heavy metal pollution in water through the adsorption of activated carbon filter element and the filtration of RO reverse osmosis membrane, which is mainly used for household water.

Electrolytic cleaning method: It is divided into electrolytic precipitation method and heavy metal electrolysis method. There are three main methods to remove heavy metal pollution in water, heavy metals can not be decomposed in water, and the toxicity is amplified after human drinking, and other toxins in the water are combined to form more toxic harmful substances.

Electrochemistry refers to the application of the basic principles of electrolysis. A method for enriching heavy metals in wastewater by electrolysis by redox reaction on the anode, cathode, and cathode respectively.

Most of the wastewater containing heavy metal ions is a complex system, and the conventional treatment method is to add ferrous sulfate, but it cannot be removed to less than 1mg l, and the discharge standard of heavy metals is, so this paper provides a deep removal method to meet the treatment needs of wastewater.

RECY-DAM-02 heavy metal remover is a solid polymer organic chelate, which can be chelated with various heavy metal ions such as Cu, Cd, Hg, Pb, Mn, Ni, Zn, Cr and other heavy metal ions in wastewater within the range of normal temperature and wide pH value conditions to form insoluble precipitates, which has the characteristics of strong complexing ability, rapid response, low addition and no secondary pollution to the water body, and is widely used in the removal of heavy metal ions in wastewater from electroplating, circuit boards, minerals and other industries.

Experimental procedure: 100 500ppm RECY-DAM-02 heavy metal remover was added to the wastewater containing heavy metals; Stir the reaction for 5 min.

Copper-nickel wastewater. Dose weighted metal scavengers.

To adjust the pH value of copper-nickel wastewater after the reaction, the pH value needs to be adjusted with a pH measuring instrument);

The treated wastewater supernatant was taken to determine the nickel content;

The data analysis is shown in the figure below).

Note: The detailed parameters of heavy metal remover RECY-DAM-02 emulsion need to be checked online.

Comprehensive measures must be adopted for the treatment of heavy metal wastewater. First of all, the most fundamental thing is to reform the production process and use less or less toxic heavy metals; Secondly, in the production process of using heavy metals, a reasonable process flow and perfect production equipment are adopted, scientific production management and operation are implemented to reduce the consumption of heavy metals and the loss of wastewater; On this basis, the wastewater with small quantity and low concentration is effectively treated. Heavy metal wastewater should be treated locally at the place of generation and not mixed with other wastewater to avoid complicating treatment.

It should not be discharged directly into the urban sewer without treatment, and mixed with the municipal sewage into the sewage treatment plant. If sludge and wastewater containing heavy metals are used as fertilizer and irrigation for farmland, the soil will be polluted, causing heavy metals to accumulate in crops. The heavy metals with the highest enrichment coefficient in crops are cadmium, nickel and zinc, while the heavy metals with the highest enrichment coefficient in aquatic organisms are mercury and zinc.

The neutralization and precipitation method is to add alkali to the wastewater containing heavy metals to carry out a neutralization reaction, so that the heavy metals are separated in the form of hydroxide precipitation that is insoluble in water. The following three aspects should be paid attention to in the actual wastewater treatment:The pH value of heavy metal wastewater is high after neutralization and precipitation treatment, and it can only be discharged after treatment. 'When the wastewater contains zinc, lead, chromium, tin, aluminum and other amphoteric metals, there is a tendency to redissolve at high pH value, and the pH value must be strictly controlled during the treatment operation, and the segmented precipitation method is implemented; The halogens, cyanide, humic acid, humus, etc. coexisting in the solution can form complexes with heavy metal ions, which has a great impact on the neutralization method, and sometimes even does not form precipitate, and pretreatment should be carried out before neutralization; Some precipitated particles are small and not easy to settle, and it is often necessary to add flocculants to assist in precipitation generation.