FeCl2 15–30% Textile Dyeing and Wastewater Treatment and ZDHC...
FeCl2 How is it used in Textile Dyeing wastewater treatment? Ferrous Chloride aids in coagulation, iron adjustment, and some decolorization/COD reduction following Jar Tests at the plant’s actual effluent parameters—it is not a “one-size-fits-all” solution for all dyeing sources.
FeCl2 (Ferrous Chloride) CAS 7758-94-3 in solution form ~15–30% per batch COA (SKU FECL2-1530); Supplied with COA/MSDS and ZDHC/MRSL compliance documentation upon customer request.
- Do not perform Jar Tests at the factory: each Textile Dyeing wastewater stream and each season/dye code may require different dosages and pH windows.
- The concentration of 15–30% must be verified against the previous batch’s COA before dosing; do not rely solely on the “FeCl2” label.
- ZDHC/MRSL compliance involves documentation, the correct batch of chemicals, and factory inventory—not just the names listed in the catalog.
This article is intended for ETP engineers, chemical warehouse managers, and procurement staff at Textile Dyeing and wet processing plants who need to understand when FeCl2 15–30% are suitable for the wastewater stream, how to interpret Jar Test results with “start and end” values, and what to do when a brand or buyer requests ZDHC/MRSL documentation from a chemical supplier. Objective: soft-decision purchasing — provide quotes based on demand, not fixed retail prices.
Why is it difficult to stabilize coagulation in textile wastewater?
Textile Dyeing wastewater is not as “uniform” as domestic wastewater. The effluent composition varies by process stage: pretreatment, bleaching, reactive/disperse/vat dyeing, washing, softening, etc. COD, color, alkalinity, salts, surfactants, and auxiliaries can fluctuate significantly even within a single day. The coagulation–flocculation–settling system (and sometimes orthophosphate/polymer) is prone to “looking good in the lab but poor in the field” if you dose based on a fixed rate from an old Jar Test.
A few common causes of cloudiness or residual color after settling:- pH window deviation—acid/alkali imbalance, dirty probe, insufficient G-value due to rapid or slow mixing.
- Coagulation source does not match the required mechanism — sometimes aluminum (PAC (Polyaluminium Chloride)) is needed, sometimes iron; sometimes Fe(II) is needed for reduction or mild Fenton reaction, sometimes only color removal or SS reduction is required.
- Active ingredient batch variation — same name “Ferrous Chloride” but COA % differs from the Jar Test batch; using old ml measurements → different results.
- Polymer “rescue” for delayed floc formation — overdosing on coagulant and then attempting to form flocs with excess polymer, increasing sludge volume and dewatering costs.
For export plants or facilities in a brand’s supply chain that require clean chemical records, “difficult-to-coagulate” materials also involve additional documentation: batch COAs, MSDS/SDS, import–export inventory, and requirements to map to the plant’s chemical catalog. That part cannot be replaced by simply “adding another drum.”
If you’re reviewing the entire chemical portfolio for the textile industry, check out the textile and Textile Dyeing chemical catalog and the specific application article on Ferrous Chloride in Textile Dyeing—this salvage article focuses on wastewater and documentation.
FeCl2 15–30%: When to Use (and When Not to)
More suitable when an ETP engineer needs a source of Fe(II) (ferrous) in a controlled redox environment to support iron coagulation, certain decolorization/COD removal processes, or when the plant has demonstrated via Jar Tests that the effluent “consumes” iron(II) salts more effectively than aluminum within the same pH window and at an acceptable sludge cost. The ~15–30% solution form, as per the COA, is more suitable for metered dosing, dilution, and inventory management than the solid form at certain wet sites.
FeCl2 Loc Thien (SKU FECL2-1530) is a Ferrous Chloride solution, CAS number 7758-94-3, with a working concentration of ~15–30%, verified by COA for each batch. We offer supply: cans / drums / tanks per order, including COA + MSDS/SDS; upon request by the buyer or brand, we can prepare ZDHC/MRSL-compliant documentation packages per batch/order — we do not claim that “every batch always meets Level N” in our catalog.
Less suitable or requires reconsideration when:
- The effluent from the Jar Test is stable with PAC at a lower pH and dosage, and the sludge is easier to dewater — do not opt for FeCl2 simply because “it contains iron.”
- The system requires pure Fe(III) or cannot control the oxidation of Fe²⁺ in open storage tanks/vessels (long-term storage, loose lids) — there is a risk of losing reducing power.
- You only need “coagulation” without locking in Fe(II) valence, pH window, or AOP/Fenton sequence — lab testing is required before scaling up.
- The brand only requests MRSL documentation, but the chemical used is outside the plant’s CIL list — paperwork cannot replace accurate inventory.
In summary: FeCl2 15–30% are tools within the textile ETP’s coagulant/iron suite, not a standalone “ZDHC key.”
Suggestions for conducting Jar Tests (lab ≠ plant SOP)
All recommendations below are a lab/Jar Test framework for engineers to adjust on their own. This is not a plant-wide dosing SOP; it does not change tank design, nor does it set a fixed ml/m³ for all wastewater sources. Reliable dosages can only be determined through Jar Tests on current water samples + batch-specific COAs + actual mixing/pH conditions.
| Suggested Steps (Lab) | Tasks | Safety / Operational Notes |
|---|---|---|
| 1. Sample preparation | Take a representative sample from the shift (avoid taking only the first or last portions), measure pH, turbidity/color, and COD if applicable | Record the dye code / production shift along with the sample |
Disclaimer: The table above provides a Jar Test framework for ETP engineers. Dosage amounts, mixing times, and pH values from the lab should not be applied directly as SOPs for plant-wide dosing. All internal procedures (PPE, dosing points, G-values, sludge treatment) are established by the plant.
When a quick comparison is needed between iron/aluminum coagulation agents before initiating a long-term Jar Test, refer to the comparison between FeCl2, FeSO4, and PAC (Polyaluminium Chloride).
ZDHC/MRSL documentation when a brand asks a supplier
Many textile and Textile Dyeing mills, as well as wastewater treatment plants (ETPs) in the export supply chain, are asked by buyers: “Do your coagulation chemicals and water treatment chemicals have documentation compliant with ZDHC guidelines?” The correct answer is typically batch-specific documentation plus the factory’s inventory records—not a “permanently ZDHC-compliant” logo affixed to every chemical drum.
From the chemical supplier’s perspective, Loc Thien Chemicals provides support on a per-order or per-batch basis:
- Batch COA (Concentration, parameters as specified in the contract);
- Current version of the MSDS/SDS;
- Chemical identification information (name, CAS 7758-94-3, solution form ~15–30% as per COA);
- ZDHC/MRSL compliance documentation package when specifically requested by the customer or brand (do not pre-claim “Level 1/2/3” for any SKU unless supported by documentation in accordance with the brand’s or mill’s program).
Quick note: ZDHC is a chemical management program for the textile supply chain (MRSL, Gateway, wastewater guidelines, etc.), not a “coagulation license.” The full definitions and modules are available in the ZDHC document hub for factories and chemical suppliers—this article does not repeat the entire Level/Gateway framework. Factory’s responsibility: map chemicals to CIL/InCheck (if applicable), ensure correct batch usage, and correct ETP injection points; supplier’s responsibility: provide batch documentation and assist with paperwork upon request.
FeCl2 helps you ensure you “have the chemical and the file” once the Jar Test is passed; it does not replace Vietnam’s QCVN standards, does not replace brand-specific wastewater testing, and does not replace the factory’s inventory management.
FeCl2 compared to PAC (Polyaluminium Chloride) and FeSO4
In textile wastewater treatment (ETP) practice, these three lines are often compared in pairs:
- PAC (Polyaluminium Chloride) — aluminum coagulation, commonly used in Jar Tests for rapid cotton treatment, with a suitable pH window for aluminum, and acceptable cost and sludge levels. Product reference: PAC tenor ~31%.
- FeSO4 — iron sulfate; used at some sites for iron coagulation or to aid in decolorization. Liquid forms: FeSO₄ and 30%.
- FeCl2 — Ferrous Chloride; preferred when controlled Fe(II) is needed, a 15–30% solution per COA, or when Jar Tests demonstrate better performance / sludge / pH compared to the other pair on the specific wastewater stream.
There is no “absolute winner.” The decision
The decision should be based on the Jar Test + TCO (chemicals + sludge + polymer + risk of failing to meet standards), not just the unit price per drum. For detailed tables and notes on pH/sludge, see the comparison between FeCl2, FeSO4, and PAC (Polyaluminium Chloride).Frequently Asked Questions
What are FeCl2 through 30%, and what are their CAS numbers?
These are Ferrous Chloride (FeCl₂) solutions with concentrations ranging from approximately 15 to 30%, as specified in the Certificate of Analysis (COA) for each batch. Standard CAS number: 7758-94-3. Loc Thien supplies via with COA/MSDS; the working concentration is always based on the batch-specific COA, not just the general label.
Does FeCl2 meet “ZDHC Level 3”?
We do not make a blanket claim in our catalog that “FeCl2 from Loc Thien always meets MRSL Level N.” What we provide: COA, MSDS/SDS, and a package of ZDHC/MRSL compliance documentation on a per-batch or per-order basis when requested by the customer or brand. Level/ChemCheck is part of the brand–mill program and requires actual documentation—not marketing claims.
What is the dosage of FeCl2 in mg/L for textile wastewater?
There is no universal safe dosage for all mills. The dosage must be determined via a Jar Test on an actual water sample, after verifying the percentage based on the COA. The table in this article is only a suggested lab guideline—not a factory SOP.
When should FeCl2 be chosen over PAC (Polyaluminium Chloride)?
When Jar Tests show that Fe(II) improves coagulation, decolorization, or COD reduction, or results in better sludge characteristics for the specific wastewater stream; or when the ETP process requires controlled iron(II) valence. If PAC is already stable, cheaper, and produces easier-to-handle sludge—stick with PAC (Polyaluminium Chloride). See details: FeCl2 vs. FeSO4 vs. PAC (Polyaluminium Chloride).
Can FeCl2 replace FeSO4?
They belong to the same iron family but have different anions and laboratory behavior. Substitution may be possible in certain cases following a Jar Test; it’s not simply a matter of “changing the name and calling it a day.” It’s also necessary to lock in the COA concentration and pH window. Product FeSO4 reference: FeSO₄ 30%.
What documentation does the factory need when purchasing FeCl2 ?
Minimum requirements: Batch COA + MSDS/SDS, delivery note, and packaging information. If the brand requests additional ZDHC/MRSL compliance documentation: clearly specify the desired file format, applicable batch, and deadline—we prepare documents on a per-order basis and do not provide “permanent certificates” for all inventory.
What should be noted when storing liquid FeCl2?
Prioritize sealed tanks or drums; avoid prolonged exposure to air to prevent oxidation; follow FIFO by batch; use materials compatible with acid and iron salts. Partial oxidation of Fe²⁺ will reduce reducing power if the process relies on the divalent form — check color, COA, and age of inventory if lab results suddenly deteriorate.
Contact us for a quote FeCl2 15–30% ()
If you need Ferrous Chloride FeCl2 solution ~15–30% per COA (SKU FECL2-1530) for Textile Dyeing ETPs—including COA/MSDS and support for preparing ZDHC/MRSL documentation as per order requirements—please provide the expected quantity (cans/drums/tanks), delivery location, and desired delivery timeframe.
We provide quotes based on actual needs; retail prices are not listed on our website. ETP engineers can include Jar Test results (pH, dosage series, key parameters) to provide context-specific advice—with the following disclaimer: operational errors and plant SOPs are your responsibility.