Acidulant Manufacturers: Citric Acid/Lactic Acid

I. Customer Pain Points

Acidulant manufacturers (citric acid, lactic acid) face three core challenges in the fermentation, extraction, and refining processes: pigment residue, insufficient optical purity, and interference from fermentation byproducts.

These issues directly threaten product quality and compliance. Pigment Residue, Substandard Product Color Citric acid fermentation broth contains melanoidins (concentration 200-1000 mg/L) and caramel color (concentration 150-800 mg/L), while lactic acid fermentation broth contains melanin (concentration 100-500 mg/L). Traditional calcium salt precipitation methods can only remove 30% of the pigments, resulting in citric acid appearing "light yellow" (color value > 8 yellow, national standard GB 1987-2007 requires ≤ 5 yellow) and lactic acid appearing "dark brown" (color value > 10 yellow, national standard GB 2023-2012 requires ≤ 6 yellow). A citric acid factory, a client of Shanxi Xinhua Carbon Technology, had 15 tons of product returned due to substandard color, resulting in a loss exceeding 600,000 yuan. Insufficient optical purity hinders access to the high-end market. Lactic acid must meet the requirements of EU EC 1333/2008 ("L-lactic acid purity ≥ 99%, D-lactic acid ≤ 1%) and US FDA 21 CFR Part 184 ("L-lactic acid content ≥ 98%). However, traditional activated carbon decolorization is not optimized for lactic acid molecules (L-lactic acid ≈ 0.6 nm, D-lactic acid ≈ 0.6 nm, but with different optical rotations). L-lactic acid adsorption loss is >15%, and D-lactic acid cannot be separated. High-end products account for only 20% (2022 industry data).

Interference from fermentation byproducts leads to insufficient product purity.

Citric acid fermentation broth contains oxalic acid (byproduct, concentration 50-200 mg/L) and gluconic acid (byproduct, concentration 30-150 mg/L), while lactic acid fermentation broth contains acetic acid (byproduct, concentration 20-100 mg/L). Traditional ion exchange methods remove less than 40% of these byproducts, resulting in citric acid purity <99.5% (national standard GB 1987-2007 requires ≥99.5%) and lactic acid purity <90% (national standard GB 2023-2012 requires ≥90%). A lactic acid plant, a client of Shanxi Xinhua Carbon Technology, suffers annual losses exceeding 500,000 yuan due to insufficient purity.

II. Application Objectives

The four core objectives for acidulant companies using activated carbon are: "color compliance, optical purity, by-product removal, and cost reduction": Deep decolorization to ensure color compliance. Through food-grade woody PAC (200 mesh), citric acid melanin is precisely adsorbed (removal rate >99%) and lactic acid melanin (removal rate >98%). Citric acid color value ≤5 (yellow) and lactic acid color value ≤6 (yellow), fully complying with national standards GB 1987-2007 and GB 2023-2012. After using it, a citric acid plant, a client of Shanxi Xinhua Carbon Technology, saw its color compliance rate increase from 60% to 99%.

Enhancing Optical Purity and Breaking into the High-End Market: Modified activated carbon (supported with chiral amines) is used for stereoselective adsorption and separation of D-lactic acid (adsorption rate > 95%), while retaining L-lactic acid (retention rate > 95%). L-lactic acid purity is ≥ 99%, and D-lactic acid purity is ≤ 0.5%, meeting EU EC 1333/2008 and US FDA standards. After using this technology, a lactic acid plant, a client of Shanxi Xinhua Carbon Technology, saw its high-end product ratio increase from 20% to 65%, and its unit price increase by 22%.

Removing Fermentation Byproducts and Improving Product Purity: Mesoporous activated carbon (50% 2-50nm) adsorbs oxalic acid (≈0.5nm) and gluconic acid (≈0.55nm) from citric acid, and acetic acid (≈0.4nm) from lactic acid, achieving a removal rate > 95%. Citric acid purity is ≥ 99.5%, and lactic acid purity is ≥ 95%. After using this technology, a citric acid plant, a client of Shanxi Xinhua Carbon Technology, saw its purity qualification rate increase from 75% to 99%.

Reduced refining costs and replacement of energy-intensive processes: The operating cost of activated carbon technology is only 0.5-1.0 yuan/ton of fermentation liquid (1/3 of that of ion exchange method), and it can be regenerated 3-5 times (regeneration cost is 30% of new carbon). A lactic acid plant, a client of Shanxi Xinhua Carbon Technology, reduced its annual refining cost from 700,000 yuan to 250,000 yuan, a decrease of 64.3%.

III. Application Significance

The application of activated carbon in acidulant companies is a core support for their "quality baseline + high-end breakthrough + compliant survival": Quality baseline: 50% of acidulant products worldwide are returned due to "color/purity defects." Activated carbon is one of the few technologies that can simultaneously remove melanoidins and pigments while retaining acidic components, directly avoiding "product scrap" (e.g., a citric acid plant, a client of Shanxi Xinhua Carbon Technology, saved 600,000 yuan/year after using it).

High-end Breakthrough: The EU and the US require L-lactic acid purity ≥99%. Activated carbon's "chiral selective adsorption" is the only low-cost process for separating D-lactic acid. After using it, one company saw its high-end product exports increase from 10 tons/month to 30 tons/month, entering the EU market.

Compliance and Survival: In 2022, 45% of environmental/quality penalties in the acidulant industry were due to "non-compliance with purity/color standards." Activated carbon is one of the few technologies that can simultaneously treat pigments and byproducts at a controllable cost, directly avoiding the risk of "production shutdown and rectification."

IV. Application History

The application of activated carbon in acidulant companies has deepened with the increasing demands for "upgraded optical purity requirements + control of fermentation byproducts":

1970s: Initial Stage. Cargill in the US first used woody PAC (100 mesh) to treat citric acid fermentation broth (containing 500 mg/L of melanoidins), reducing the color value from 12 yellow to 5 yellow through "adsorption-filtration," becoming the world's first case of using activated carbon to improve the color of acidulants.

2020s: The Intelligent Era. China's "14th Five-Year Plan for Food Industry Development" requires "acidifier byproduct removal rate ≥90%." Activated carbon, combined with an "online color value/purity monitoring + automatic dosing" system, achieves precise adsorption (e.g., automatically adjusting PAC dosage based on the concentration of melanin in citric acid fermentation broth), reducing operating costs by 25%.

V. Mechanism of Action

Activated carbon solves the problems of "unacceptable color, insufficient optical purity, and interference from byproducts" in acidulants through a triple action of "physical adsorption + chiral selectivity + pore size matching":

1. Physical Adsorption: "Targeted Sieving" of the Pore Structure

• Mesopores (2-50nm): Accounting for 50% of the total pore volume (specifically designed for acidulant molecules), it adsorbs medium-molecular-weight pigments (melanoidins ≈ 0.8nm, melanin ≈ 0.9nm) through van der Waals forces, achieving an adsorption capacity of 300-500mg pigment/g of char (twice that of ordinary activated carbon), with an adsorption loss rate of <5% for acidulant components (citric acid ≈ 0.55nm, L-lactic acid ≈ 0.6nm).
• Micropores (<2nm): Serving as a "deep purification channel," it adsorbs small-molecule byproducts (oxalic acid ≈ 0.5nm, acetic acid ≈ 0.4nm), with a removal rate >95%. 1. **Macropores (>50nm):** Serving as an "inlet channel," allowing large suspended molecules (>1μm) to enter the activated carbon interior, reducing the load on subsequent filtration.

2. Chiral Selectivity: "Stereoscopic Recognition" of Surface Functional Groups.

Chiral amines (-NH-CH₃, chiral centers) loaded on the activated carbon surface preferentially adsorb D-lactic acid (configurationally matched) through stereomatching, achieving an adsorption rate >95%, while retaining L-lactic acid (configurationally mismatched) at >95%, thus achieving optical separation.

3. Synergistic Regeneration: A "Key Step" in Cost Reduction.

Powdered activated carbon (PAC): After being mixed with acidulant residue, it is regenerated through high-temperature incineration (850℃), achieving a heat recovery rate >80%. The ash can be used as fertilizer raw material (nitrogen content ≥3%). Granular Activated Carbon (GAC): Through steam regeneration (180-200℃, 0.3MPa), the adsorbed pigments are desorbed into gaseous organic matter, which is then incinerated in a boiler (calorific value ≥15000kJ/kg). The regenerated carbon's adsorption capacity is restored to 85% of that of new carbon, and the cost is only 30% of that of new carbon.

VI. Application Methods

Acidulant companies use a combined process of "fermentation broth decolorization (PAC) + optical purification (chiral GAC) + byproduct removal (mesoporous GAC)" to cover all scenarios related to "citric acid and lactic acid":

1. Citric Acid/Lactic Acid Decolorization: Food-grade PAC adsorption

• Applicable Scenarios: Citric acid fermentation broth (melanoidins 200-1000mg/L, color value >8 yellow), lactic acid fermentation broth (melanin 100-500mg/L, color value >10 yellow). Process Steps:
• Pretreatment: Citric acid fermentation broth → filtration (removal of mycelium, SS ≤ 50 mg/L); Lactic acid fermentation broth → neutralization tank (Ca(OH)₂ adjusts pH = 10).
• PAC Adsorption: Fermentation broth enters the adsorption tank, add 50-100 mg/L of wood-based food-grade PAC (200 mesh, iodine value ≥ 1000 mg/g, ash content ≤ 3%), stir for 20 minutes, citric acid color value ≤ 5 (yellow, melanin removal rate > 99%), lactic acid color value ≤ 6 (melanin removal rate > 98%).
• Separation: Separate PAC and fermentation broth using a plate and frame filter press (filter cake moisture content ≤ 60%).

2. Lactic Acid Optical Purification: Chiral GAC Fixed Bed

Applicable Scenarios: Crude lactic acid extract (L - lactic acid purity 95%, D - lactic acid 5%). Process Steps:
1. Crude Extract → Chiral Granular Activated Carbon (GAC, Φ3-6mm, loaded with chiral amines, iodine value ≥900mg/g) Fixed Bed → Flow Rate 5-10m/h, Contact Time 20-30 minutes → Discharge: L-lactic acid purity ≥99%, D-lactic acid ≤0.5%.

2. Citric Acid Byproduct Removal: Mesoporous GAC Fixed Bed

Applicable Scenarios: Citric acid refining solution (containing oxalic acid 50-200mg/L, gluconic acid 30-150mg/L, purity <99.5%).

Process Steps:
Refined Solution → Mesoporous GAC (Φ3-6mm, mesoporous content 50%, iodine value ≥900mg/g) Fixed Bed → Flow Rate 5-8m/h → Oxalic acid <5mg/L, gluconic acid <3mg/L, purity ≥99.5%.

VII. Application Process

Taking a lactic acid plant (annual production of 10,000 tons of L-lactic acid, fermentation broth containing 300 mg/L melanin and 5% D-lactic acid, purity 95%), a cooperative client of Shanxi Xinhua Carbon Technology, as an example:

• Fermentation broth pretreatment: Lactic acid bacteria fermentation → Fermentation broth (300 mg/L melanin, 5% D-lactic acid) → Filtration (removal of bacteria, SS ≤ 30 mg/L) → Ca(OH)₂ neutralization (pH = 10).
• PAC decolorization: The neutralized solution enters the adsorption tank (2 tanks, 500 m³ each), adds woody PAC (200 mesh, 50 mg/L), stirs for 20 minutes → Plate and frame filter press → Filtrate melanin < 5 mg/L, color value 5 (yellow).
• Chiral GAC Purification: Filtrate enters a chiral GAC fixed bed (2 units, each with 15 tons of char, Φ3-6mm, loaded with chiral amines) → Flow rate 8m/h, contact time 25 minutes → Output L-lactic acid purity 99.2%, D-lactic acid 0.4%.
• Refining and Drying: Purified liquid → Ion exchange (Ca²⁺ removal) → Concentration (60°Bé) → Spray drying (180℃, 10 seconds) → L-lactic acid powder (purity 99.2%, conforming to EU EC 1333/2008) → Packaging.
• Regeneration and Reuse: After GAC saturation → Steam regeneration furnace (180℃, 0.3MPa) → Desorption gas sent to boiler for incineration → Regenerated char returned to the fixed bed.

PAC sludge → Plate and frame filter press (60% moisture content) → High-temperature incinerator (850℃) → Ash residue to produce organic fertilizer (3% nitrogen content).

VIII. Application Effects

After the upgrade, a lactic acid plant saw a significant improvement in its core performance indicators (based on actual operational data from a client of Shanxi Xinhua Carbon Technology):

Indicators	Before the modification (calcium salt precipitation method)	Modified (PAC + Chiral GAC)	Increase/Decrease:	Compliance Status:
Melanin Residue (mg/L)	300	＜5	Decrease by 98.3%	Color Compliant
L-Lactic Acid Purity (%)	95	99.2	Increase by 4.4%	Compliant with EC 1333/2008
D-Lactic Acid Content (%)	5	0.4	Decrease by 92%	Compliant with FDA 21 CFR Part 184
Annual Refining Cost (RMB 10,000)	70	25	Decrease by 64.3%	—
Percentage of High-End Products (%)	20	65	Increase by 225%	—
Annual Return Loss (RMB 10,000)	50	2	Decrease by 96%	—

IX. Core Advantages

Customized solutions for acidulant companies offer four irreplaceable advantages:
Highly Targeted Products Matching Acidulant Characteristics: The developed wood-based food-grade PAC (200 mesh, iodine value ≥1000mg/g) specifically adsorbs melanin and other pigments, achieving a pigment removal rate >98%; chiral GAC (supported chiral amines) specifically separates D-lactic acid, achieving a D-lactic acid removal rate >95% and an L-lactic acid retention rate >95%.

High Optical Purity, Breaking into the High-End Market: Chiral activated carbon achieves L-lactic acid and D-lactic acid separation through "stereoselective adsorption," achieving L-lactic acid purity ≥99% (National Standard GB 2023-2012 requires ≥90%). After using this solution, a lactic acid plant, a client of Shanxi Xinhua Carbon Technology, saw its high-end product exports increase from 10 tons/month to 30 tons/month.

Compliant and Reliable, with Full Qualification Coverage: Products are certified to GB 29215-2012 "Food Additives - Activated Carbon", FDA 21 CFR Part 178.3520, and EU EC 1333/2008, fully meeting global acidulant industry standards.

Controllable Costs, High Cost-Effectiveness Throughout the Life Cycle:

• Chiral GAC: Can be regenerated 3-5 times (regeneration cost is 30% of new carbon), initial investment is only 1-1.8 million RMB/10,000 tons annual capacity;
• PAC Decolorization Process: Operating cost 0.5-1.0 RMB/ton fermentation liquid (1/3 of the calcium salt precipitation method), a citric acid plant, a partner of Shanxi Xinhua Carbon Technology, reduced its annual refining cost by 60% (from 600,000 RMB to 240,000 RMB).

X. Cost Analysis

A cost comparison between activated carbon and traditional processes, using a 10,000-ton-per-year L-lactic acid plant as an example:

Project	PAC+Chiral GAC process	Calcium salt precipitation method + ion exchange
Initial Investment (RMB 10,000)	120-200	200-300
Operating Cost (RMB/ton of fermentation broth)	0.5-1.0	1.5-2.0
Maintenance Cost (RMB 10,000/year)	15-30	50-80
Total Life Cycle Cost (RMB/ton of fermentation broth)	1.0-1.5	3.0-4.0
Premium for High-End Products (RMB 10,000/year)	80-100	0

XI. Why Choose Us?

Performance Endorsement: Our activated carbon has received consistent praise for its thorough decolorization and high optical purity. A lactic acid plant, a client of Shanxi Xinhua Carbon Technology, saw its L-lactic acid purity increase from 95% to 99.2% and the proportion of high-end products rise from 20% to 65% after using our PAC + chiral GAC.

Technical Strength: We optimize the pore structure for acidulant molecules (citric acid ≈ 0.55nm, L-lactic acid ≈ 0.6nm), developing "chiral amine-loaded GAC" and "GAC with 50% mesopore content," achieving a D-lactic acid removal rate >95%, solving the pain point of traditional processes' inability to separate optical isomers.

Global Service: We have production bases in Shanxi, Ningxia, and Fujian (annual capacity of 45,000 tons), supporting "customized production + localized delivery." For overseas clients, we provide a full-process service including "activated carbon selection + process design + compliance certification," ensuring a response time of 72 hours.