Activated Carbon for Citric Acid Purification
Food-grade powdered activated carbon for decolorizing citric acid fermentation broth and mother liquor — stripping color bodies, iron and organic by-products so the acid crystallizes bright, pure and food-safe.
The Purification Challenge
Why citric acid needs carbon decolorization
Citric acid is produced by submerged fermentation of sugar feedstocks with Aspergillus niger. The resulting broth carries melanoidins and other color bodies, residual sugars, proteins, trace metals (especially iron) and organic by-products that would otherwise carry through to the crystal. Before crystallization, the clarified liquor is treated with powdered activated carbon to adsorb color and impurities, giving a colorless solution that yields bright, high-purity citric acid crystals meeting FCC and E330 food-additive specifications. Low-iron, high-methylene-blue carbon is essential — iron discolors the product and catalyzes degradation.
How Citric Acid Decolorization Works
From fermentation broth to bright crystals
After fermentation and calcium citrate recovery, the acidified liquor is filtered to remove biomass and gypsum. This clarified but still-colored liquor is the feed for carbon treatment.
Powdered activated carbon is dosed at 0.5–2% (w/w on solids) into the liquor and mixed for 20–60 minutes. The pore network adsorbs melanoidins, residual protein, iron and organic by-products.
Spent carbon is removed on filter presses, leaving a water-white liquor. The purified solution is concentrated and crystallized into bright, food-grade citric acid.
Where It's Used
Citric acid & citrate products we supply carbon for
Carbon Selection
Choosing carbon by purification duty
Match the grade to your color load and iron target. Every lot ships with a batch COA — methylene blue, iodine, ash, moisture and heavy metals.
| Purification Duty | Recommended Grade | Key Spec | Form |
|---|---|---|---|
| Broth / liquor decolorization | Wood-based PAC, high MB | MB ≥180 mg/g | Powder |
| Deep color & iron removal | Wood-based PAC, acid-washed | Low ash, low iron | Powder |
| Fine polishing before crystallization | Coconut-based PAC, food-grade | Low ash ≤3% | Powder |
| Mother liquor recycle | Wood-based PAC, cost-optimized | MB ≥160 mg/g | Powder |
Not sure which grade fits your color load and iron target? Send us a sample.
Get a Grade RecommendationProcess Design
Bright crystals and stable color at lowest cost
Dose & contact time
Powdered carbon at 0.5–2% w/w on dissolved solids, mixed 20–60 minutes at 60–80°C. Higher color loads need more carbon; optimize by bench trial to control cost and yield loss on the spent cake.
Low iron is critical
Iron discolors citric acid crystals and catalyzes degradation. Acid-washed, low-ash carbon adds no extractable iron, keeping the product bright and stable through crystallization and storage.
High methylene blue
Melanoidins and fermentation color bodies are large molecules. A high methylene-blue (MB ≥180 mg/g) wood-based PAC with mesopore volume adsorbs them efficiently where micropore-only carbon struggles.
Food-grade compliance
Carbon for citric acid must meet food-contact limits on heavy metals. Our grades are food-grade with batch COA, supporting FCC, E330 and pharmaceutical specifications for the finished acid.
Technical Specifications
| Parameter | Wood PAC (Decolorizing) | Coconut PAC (Polishing) |
|---|---|---|
| Methylene Blue | ≥180 mg/g | — |
| Iodine Number | ≥800 mg/g | ≥950 mg/g |
| Mesh / Form | 200 mesh powder | 200 mesh powder |
| Ash Content | ≤4% | ≤3% |
| Iron (Fe) | Low / acid-washed | Low |
| Moisture | ≤10% | ≤5% |
| Certification | FCC / HALAL / KOSHER | FCC / HALAL / KOSHER |
Field Performance
Proven across citric acid plants
Case: citric acid producer brightens crystal color
A citric acid fermentation plant switched to a high-methylene-blue acid-washed wood-based PAC for its liquor decolorization step. The carbon stripped melanoidin color bodies and residual iron that the previous grade left behind, delivering a water-white liquor and noticeably brighter crystals — meeting FCC color limits with a lower dose and less yield loss on the spent cake.
Recommended Products
These are the grades we recommend most often for citric acid decolorization. Contact us for a tailored recommendation.
Wood-Based Powdered Activated Carbon (PAC)
Citric acid decolorization, high methylene blue
Coconut Shell Powdered Activated Carbon (PAC)
Fine polishing before crystallization, low ash
Wood-Based Activated Carbon (Series)
Range of decolorizing grades for organic acids
Citric Acid Carbon — Frequently Asked Questions
What activated carbon is best for citric acid purification?
A food-grade, high-methylene-blue wood-based powdered activated carbon (MB ≥180 mg/g), ideally acid-washed and low in iron. Citric acid color bodies (melanoidins) are large molecules, so mesopore-rich wood PAC decolorizes better than micropore-only carbon. Low iron is essential to keep crystals bright.
How much carbon is used in citric acid decolorization?
Typically 0.5–2% of the dissolved solids by weight, mixed for 20–60 minutes before filtration. The exact dose depends on the color load of the broth or mother liquor and is optimized by bench trial to balance color removal, cost and yield loss on the spent carbon.
Why does the carbon need to be low in iron?
Iron discolors citric acid crystals and can catalyze degradation during concentration and storage. Acid-washed, low-ash carbon has minimal extractable iron, so it removes impurities from the liquor without adding metals back into the product.
Can I use the same carbon for citric acid and MSG?
Yes — both are fermentation-derived products decolorized with high-methylene-blue wood-based PAC. The grade is very similar; we supply the same family of food-grade decolorizing carbons for citric acid, MSG and amino acid purification. Tell us your color target and we'll match the spec.
Is it food-grade and certified?
Yes. Our citric acid decolorization carbon is food-grade with heavy-metal extractables below food-contact limits, supporting FCC and E330 specifications. It ships with HALAL, KOSHER and ISO 9001 documentation and a batch COA on every lot.
What is the minimum order and lead time?
MOQ is 1 ton, with free samples available for bench trials. Standard lead time is 10–15 days factory-direct. We can supply 25 kg bags or 500 kg jumbo bags, with custom private-label packaging on request.
Brighter citric acid at lower carbon cost
Tell us your broth or liquor color, iron target and throughput. We'll recommend the food-grade grade and dose, and send a free sample to trial before crystallization — with a batch COA on every shipment.
Request a Citric Acid Carbon Quote