Iron-Carbon Micro-Electrolysis
Faced with complex wastewater from industries such as printing and dyeing, pharmaceuticals, chemicals, and electroplating—characterized by "high color, high toxicity, and poor biodegradability (B/C often below 0.2)"—traditional biological treatment often falls into the dilemma of "can accept it, but cannot degrade it," while direct advanced oxidation is costly. Iron-carbon micro-electrolysis (internal electrolysis) uses iron scraps and carbon packing to form countless microscopic galvanic cells, enabling in-situ chain scission, decolorization, and biodegradability improvement without external current, "reducing the load and opening the way" for downstream biological or Fenton treatment.
I. Product Positioning
The iron-carbon micro-electrolysis reactor (also known as an internal electrolysis tank / iron-carbon packed bed) is an advanced oxidation pretreatment equipment for refractory organic wastewater and complex wastewater. The equipment is filled with cast iron scraps—carbon (or regular iron-carbon) packing. Under acidic conditions, iron (anode) corrodes and dissolves Fe²⁺, while the carbon (cathode) surface reduces to produce highly active "nascent hydrogen [H]." Together, they synergistically perform redox reactions, ring opening and chain scission, and destruction of chromophoric and complexing groups. The entire unit requires no external power supply and is driven by iron scrap consumption. It is often used as a front-end unit for "chain scission and quality improvement," followed by neutralization sedimentation or Fenton advanced oxidation. It is a typical "treating waste with waste" green pretreatment process.
II. Working Principle (Brief)
Influent pH adjustment: Raw water is acidified to acidic conditions (pH about 2–4) to provide a suitable reaction environment for the iron-carbon micro-cells.
Iron-carbon micro-cell reaction: Iron (anode) corrodes and dissolves Fe²⁺, while the carbon (cathode) surface reduces to produce nascent hydrogen [H], forming countless microscopic galvanic cells in the reactor.
Redox chain scission: Nascent [H] and Fe²⁺ reductively destroy chromophoric groups, open rings and break chains, and cleave heavy metal-complexing agent bonds.
Flocculation and co-precipitation: Dissolved Fe²⁺ is oxidized to Fe³⁺ upon contact with air and hydrolyzes into iron salt flocs, which enmesh and co-precipitate some pollutants.
Biodegradability improvement: Macromolecular refractory substances are converted into small molecular fragments, significantly raising the B/C ratio and "unleashing" subsequent biological treatment.
Effluent post-treatment: pH is adjusted back for neutralization and sedimentation (or in-situ Fe²⁺ is directly supplemented with H₂O₂ for Fenton advanced oxidation), then enters the biological system.
Process schematic: Acidic raw water → iron-carbon packed bed (micro-cell reaction) → chain scission and decolorization / flocculation → neutralization sedimentation (or Fenton) → pretreated effluent with improved biodegradability
The core mechanism lies in the "iron-carbon" galvanic cell effect: iron provides electrons and Fe²⁺, carbon provides cathodic reduction sites, and the strong reducing power of nascent [H] and Fe²⁺ preferentially attacks chromophoric groups, conjugated double bonds, and coordination bonds, cracking pollutants from "refractory macromolecules" into "easily degradable small molecules," thereby "nurturing" biodegradability.
III. Core Advantages
① No external power, treating waste with wasteDriven by the galvanic cells of the iron-carbon packing itself, no external current is required. Iron scraps are the consumable, and operating energy consumption is low, aligning with green carbon reduction.
② Chain scission, decolorization, and toxicity reductionRing opening and chain scission, destruction of chromophoric groups and complexing bonds, with significant decolorization and detoxification effects on high-color, high-toxicity wastewater.
③ Significantly improves biodegradabilityB/C can be increased from <0.2 to 0.3–0.5, turning "dead water" into "living water" and greatly reducing the downstream biological load.
④ In-situ synergistic flocculationThe Fe²⁺/Fe³⁺ generated in the reaction also provides coagulation, potentially eliminating the need for external coagulants in some cases.
⑤ Shock resistance, adapts to high concentrationsCertain tolerance to high COD, high color, high salinity, and wastewater containing refractory substances, with good operational flexibility.
⑥ Simple structure, easy to retrofitCarbon steel anti-corrosion / PP / rubber-lined tank bodies are all acceptable. Above-ground or buried layout, modular assembly, easy to integrate into existing plant upgrades.
IV. Main Technical Parameters (Reference Range)
Item | Parameter Range / Description |
|---|---|
Applicable pH | Acidic operation, influent pH about 2–4 (requires acid adjustment) |
Hydraulic retention time (HRT) | 30–120 min, depending on water quality concentration and removal target |
Iron-carbon packing | Cast iron scraps—carbon or regular iron-carbon packing, particle size about 10–30 mm, filling rate according to design |
Influent COD adaptability | Medium to high concentration refractory wastewater, thousands to tens of thousands mg/L can be pretreated |
Decolorization rate | 60–95%, varies greatly depending on dye / chromophoric substance type |
COD pretreatment removal rate | 15–40% (mainly for chain scission and quality improvement, not direct reduction as the goal) |
Biodegradability improvement | B/C can be increased from <0.2 to 0.3–0.5 |
Iron consumption | Iron scrap replenishment about 5–30 kg/t wastewater (depending on water quality) |
Material and layout | Carbon steel anti-corrosion / PP / concrete rubber-lined, above-ground or buried, modular |
Supporting units | Acid dosing system, aeration (optional), neutralization sedimentation / Fenton post-treatment |
* The above are typical reference ranges. Actual dosage, retention time, and decolorization/removal effects should be determined by water quality bench tests and on-site commissioning.
V. Typical Application Scenarios
Scenario / Industry | Adaptability Description / Main Removal Targets |
|---|---|
Printing and dyeing / dye wastewater | High color, containing azo/anthraquinone chromophoric groups, chain scission and decolorization, biodegradability improvement |
Pharmaceutical / pesticide wastewater | Toxic and hazardous, containing benzene rings/halogenated/nitro refractory substances, detoxification and ring opening |
Chemical / fine chemical | Refractory organic wastewater containing conjugated and complex structures, chain scission and quality improvement |
Electroplating / circuit boards | Cleavage of complexed heavy metals such as EDTA and chelating agents, facilitating subsequent precipitation and recovery |
Landfill leachate | Pretreatment of mature/refractory sections, toxicity reduction, raising B/C for biological treatment |
Coking / coal chemical | Containing phenols, polycyclic aromatic hydrocarbons and other refractory substances, chain scission and detoxification |
Paper / pulping | Lignin coloration, poor biodegradability, decolorization and biodegradability improvement |
VI. Applicable Boundaries and Selection Recommendations
Iron-carbon micro-electrolysis is positioned as a pretreatment unit. The effluent must still undergo biological or advanced treatment to meet standards and cannot replace end-of-pipe treatment; its value lies in "turning refractory water into biodegradable water." The process must operate under acidic conditions, and acid adjustment increases acid consumption and equipment corrosion. The packed bed and piping must be properly corrosion-protected.
Boundaries with similar technologies must be clarified: Electrocoagulation relies on external current to dissolve electrodes and replace chemicals with electricity, while iron-carbon micro-electrolysis requires no external power and relies on spontaneous Fe—C galvanic cell reactions; Fenton requires external addition of large doses of H₂O₂ and Fe²⁺, whereas micro-electrolysis generates Fe²⁺ and [H] in situ without external H₂O₂. In engineering, the two are often combined in series as "micro-electrolysis + Fenton" to reduce costs and improve efficiency. In terms of operation and maintenance, attention must be paid to iron-carbon packing compaction, passivation, and iron consumption replenishment, along with supporting sedimentation separation of the generated iron sludge.
FAQ
How much does this equipment cost?
The price varies by treatment capacity, water quality, materials and configuration, so a custom quote is provided based on your actual conditions. We offer free water testing and solution design, with a detailed quote within 1 working day after requirements are confirmed.
What treatment capacity is available? Can it be customized?
Capacity is fully customizable, ranging from tens to thousands of tons per day (e.g. 0.5–30 m³/h), with non-standard design support matched precisely to your inlet/outlet requirements.
How long does delivery take?
Standard equipment typically takes about 2–4 weeks to produce; custom projects depend on scale and process. The delivery date is confirmed at contract signing, with design, manufacturing and shipping progressing on schedule.
Is installation and commissioning included?
Yes. We provide installation, system commissioning, operator training and environmental acceptance assistance, as well as long-term managed operation services on request.
What about after-sales and warranty?
We provide a warranty period and a 24/7 technical hotline, with free repair for non-human faults during the warranty period, plus spare parts supply and regular inspection services.
Let hard-to-treat water be "electrolyzed" first to open the way
Rihong Environmental can provide water quality bench tests, process selection, and complete equipment solutions for iron-carbon micro-electrolysis reactors. Welcome to call or leave a message to obtain a customized pretreatment design.
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