Analysis of iron carbon micro electrolysis technol

Analysis of iron carbon micro electrolysis technology for wastewater treatment

iron filings (mostly cast iron filings) are iron carbon alloys. When immersed in wastewater solution, they form a complete micro battery circuit and form an internal electrolytic reaction, which is micro electrolysis. When inert carbon (such as graphite, coke, activated carbon, coal, etc.) particles are added to the cast iron chips, the iron chips contact with the carbon particles to form a large galvanic cell, which is iron carbon micro electrolysis

2. Technical principle

iron carbon micro electrolysis technology mainly uses the reduction of iron, the electrochemistry of iron, and the flocculation and adsorption of iron ions to purify wastewater

the electrolytic material of iron carbon micro electrolysis process generally adopts cast iron chip material to change the transfer and maintenance of the experimental machine: before the mechanical transfer to the construction site and activated carbon or coke, when the material is immersed in industrial wastewater (such as coking wastewater and electroplating wastewater), internal and external electrolytic reactions occur. On the one hand, cast iron contains a small amount of iron carbide, and there is an obvious oxidation-reduction potential difference between iron carbide and pure iron. In this way, many fine primary batteries are formed inside the cast iron chips. Pure iron is used as the anode of the primary battery, and iron carbide is used as the cathode of the primary battery. Electrochemical reactions occur in aqueous solutions containing acidic electrolytes, making iron change into ferrous ions and enter the solution. In addition, the cast iron chips and the surrounding carbon powder form a large primary cell, so the process of using micro electrolysis for wastewater treatment is actually a process of internal and external double electrolysis, or it is called the existence of micro and macro primary cell reaction on a global scale. In addition, in order to increase the potential difference and promote the release of iron ions, a certain proportion of catalyst used in the aerospace industry, including supported scaffolds, can also be added to the iron carbon micro electrolysis filler

the electrochemical reaction process is as follows:

anode (FE): fe-2e → fe2+e (fe/fe2+) =0.44v

cathode (c): 2h++2e → H2E (h+/h2) =0.00v

in the reaction, primitive fe2+ and atomic h are produced, which have high chemical activity, can change the structure and characteristics of many organic substances in wastewater, and make organic substances break chains and rings

if there is aeration, the following reactions will occur to avoid the tissue change reaction caused by heating:

o2+4h++4e → 2h2oe (O2) =1.23v

o2+2h2o+4e → 4oh-e (o2/oh-) =0.41v

fe2++o2+4h+ → 2h2o+fe3+

the oh- generated in the reaction is the reason for the increase in the pH value of the effluent, and the fe3+ generated by fe2+ oxidation is gradually hydrolyzed to form Fe (OH) 3 with high degree of polymerization.Colloidal flocculant can effectively adsorb It condenses suspended solids and heavy metal ions in water, and its adsorption performance is much higher than that of general Fe (OH) 3, so as to enhance the purification effect of wastewater

3. Process flow

iron carbon electrode reaction needs to be carried out under acidic conditions to achieve better results. Therefore, before the reaction, the pH value of the wastewater needs to be adjusted to 3-4, and after the reaction, the pH value is about 5.7. Generally, in order to remove fe2+ and fe3+ in the wastewater, alkali needs to be added to adjust the pH value of the effluent to weak alkalinity

4. Process characteristics

1. Fast reaction speed. The filler adopts microporous activation technology, with large specific surface area and catalyst, which provides greater current density and better micro electrolysis reaction effect for wastewater treatment. The reaction rate is fast. Generally, industrial wastewater only takes minutes, and the long-term operation is stable and effective

2. Wide range of pollutants. The micro electrolysis treatment method can achieve the effect of phosphorus removal by chemical precipitation, and can also remove heavy metals by reduction. It has a good degradation effect on refractory organic substances containing even fluorine, carbon double bond, nitro and halogenated group structures

3. It is easy to operate. The regular micro electrolytic filler has a long service life, and it is easy to operate and maintain. Only a small amount of micro electrolytic filler is consumed in the process of treatment. It only needs to be added regularly without replacement, which greatly reduces the maintenance labor intensity

4. Reduce secondary pollution. After micro electrolysis treatment, the wastewater will form original ferrous or iron ions in the water, which has better coagulation effect than ordinary coagulants, and there is no need to add coagulants such as iron salts. The removal rate of COD is high and will not cause secondary pollution to water

5. Various application methods. The product can also be used in the treatment project of high concentration organic wastewater that has not reached the standard. It is used for the pretreatment of wastewater, which can ensure the stable discharge of wastewater after treatment. It can also lead out the high concentration part of production wastewater separately for micro electrolysis treatment

5. Existing problems

1 Iron filings caking and surface passivation: after using this technology to treat wastewater for a long time, organic matter will deposit on the iron electrode, forming a passive film, which prevents the iron electrode and carbon from forming a stable primary battery. In addition, iron carbon fillers are easy to harden, which hinders the effective contact between wastewater and fillers and forms a short flow, thus reducing the treatment effect of wastewater

2. Effluent discoloration: because iron filings are oxidized into fe2+ ions and then generate fe3+, their hydrolysates Fe (OH) 2 and Fe (OH) 3 are the main causes of discoloration, and the fe2+ not completely removed will aggravate this "discoloration" phenomenon to a certain extent

3. Produce iron mud: This is easy to handle, and can be sent to the iron refinery or mixed to make building materials

6. Types of applicable wastewater

1 Dye and printing and dyeing wastewater; Coking wastewater; Petrochemical wastewater

-- while decolorizing the above wastewater, the bod/cod value of the treated water is significantly increased

2. Petroleum wastewater; Leather wastewater; Papermaking wastewater and wood processing wastewater

-- the bod/cod value of the above wastewater after treatment is greatly increased

3. Electroplating wastewater; Printing wastewater; Mining wastewater; Other wastewater containing heavy metals

-- heavy metals can be removed from the above wastewater

4. Organic phosphorus agricultural wastewater; Organochlorine agricultural wastewater

-- greatly improve the biodegradability of the above wastewater, and remove phosphorus and sulfide