1.2.2 Segmentation of Product Forms by Different Processes

1. Ferrous sulfate heptahydrate crystalline granular type (main force in water treatment): particle size range 0.5-2.0mm, light green large granular crystals, excellent fluidity, not easy to generate dust, moderate dissolution rate, suitable for most general industrial scenarios such as municipal sewage, industrial wastewater, sludge dewatering, etc. It has low production cost, the highest cost performance, and accounts for more than 80% of the market circulation.
2. 
   
3. Ferrous sulfate heptahydrate powder type: particle size ≤ 0.5mm, light green powder, extremely fast dissolution rate, suitable for small sewage treatment equipment, precise dosing, and rapid dissolution reaction scenarios. It has slightly more dust, is easy to absorb moisture, and is suitable for short-term use and small-batch procurement.
4. 
   
5. Ferrous sulfate monohydrate powder type: particle size ≤ 0.3mm, light green ultra-fine powder, high effective content, fast dissolution rate, suitable for scenarios such as high-standard sewage treatment, chemical synthesis, feed addition, etc. It has weak hygroscopicity, is not easy to agglomerate, and is suitable for long-term storage and long-distance transportation.
6. 
   
7. Ferrous sulfate monohydrate granular type: particle size 0.3-1.0mm, light green dry granules, dust-free, non-hygroscopic, with optimal fluidity. It is suitable for automatic feeding, large-scale dosing in large sewage treatment plants, and long-distance transportation. It has extremely strong stability and is the preferred product for high-end environmental protection projects.

8. 1.2.3 Characteristics of Appearance Changes in Product Storage State

   Industrial-grade solid ferrous sulfate is a product that is easy to oxidize and absorb moisture. Its appearance will change significantly with storage conditions and storage time, which can be used to intuitively judge the degree of product quality degradation. The specific change characteristics are as follows:

   
   

   • Normal sealed storage (cool and dry, humidity ≤ 60%): Ferrous sulfate heptahydrate remains in a light green crystalline state, without caking or discoloration, with normal fluidity, and the attenuation of ferrous ion content is ≤ 1%; Ferrous sulfate monohydrate remains in an off-white state, without oxidation or deliquescence, with stable active ingredients within the shelf life, fully meeting the requirements of industrial use.
   • 
     
   • Slight moisture-induced oxidation (humidity > 65%, poor sealing): The local surface of the product turns pale yellow or rust-colored, with slight adhesion, no large agglomerates, a slight decrease in water solubility, and a 2%-5% attenuation of ferrous ion content. It can be used in non-precision scenarios such as ordinary sewage treatment and soil improvement, without affecting the basic use effect.
   • 
     
   • Severe moisture-induced oxidation (long-term exposure, rainwater ingress): Ferrous sulfate heptahydrate turns entirely yellowish-brown or rust-colored, with large-area caking and hardening. It feels moist and sticky to the touch, has a slower dissolution rate, and its aqueous solution is turbid and yellowish. The content of ferrous ions (divalent iron) decreases by more than 10%, and its flocculating and reducing properties are significantly reduced; After oxidation, ferrous sulfate monohydrate turns into a pale yellow powder, with severe caking and loss of active ingredients, making it an unqualified product.
   • 
     
   • High-temperature exposure oxidation (storage temperature > 35℃): Ferrous sulfate heptahydrate crystals dehydrate, darken in color, rapidly oxidize to ferric iron (trivalent iron), agglomerate and harden, completely losing its flocculating and reducing properties; Ferrous sulfate monohydrate has slightly better stability at high temperatures, but long-term exposure to sunlight will also cause oxidation and yellowing, with a significant decline in quality.
   • 
     
   • 

   • 1.3 Core Physical and Chemical Properties of Industrial-grade Solid Ferrous Sulfate

     1.3.1 Core Physical Properties (National Standard Test Values)

     Physical and chemical index items	Measured indicators of ferrous sulfate heptahydrate	Measured indicators of ferrous sulfate monohydrate	Indicator Description
     Relative density (at 25℃ room temperature)	1.89	2.97	The content of crystal water is different, and the density varies significantly.
     Melting point/decomposition temperature	64℃ (loses crystal water)	300℃ (complete decomposition)	Heptahydrate loses water at high temperature, and monohydrate decomposes into iron oxide at high temperature
     Water solubility (20℃, g/100mL distilled water)	26.5, very soluble in water	29.1, extremely soluble in water	Dissolves quickly at room temperature, and the aqueous solution is light green
     Solubility in organic solvents	Insoluble in organic solvents such as ethanol, ether, and acetone	Insoluble in most organic solvents	Only soluble in water, suitable for water-based industrial process scenarios
     Aqueous solution pH value (50g/L aqueous solution, 25℃)	3.5-4.5	3.0-4.0	Weakly acidic, with acidity slightly stronger than that of ferrous sulfate heptahydrate
     Hygroscopicity	Strong, easily hygroscopic and oxidizable	Weak, not easy to absorb moisture in a dry state	Ferrous sulfate heptahydrate must be strictly sealed to prevent moisture, while ferrous sulfate monohydrate is easier to store.
     Odor characteristics	Slight sulfuric acid odor, no unusual smell	Almost no peculiar smell	A rusty smell or a foul odor indicates that the product has oxidized and deteriorated.
     Room temperature stability	Stable when dry and sealed, but oxidizes quickly in humid air	Extremely stable in a sealed state	After oxidation, ferrous iron (divalent iron) turns into ferric iron (trivalent iron), and its performance becomes ineffective.

     1.3.2 Core Chemical Properties

     1. Strong reducibility (core industrial characteristic): It is the core chemical property of industrial-grade solid ferrous sulfate. The ferrous ions (Fe²⁺) in the molecule are easily oxidized to ferric ions (Fe³⁺), and it has extremely strong reducing ability. It can reduce high-valence toxic and harmful substances in industrial wastewater (such as hexavalent chromium, permanganate ion, hypochlorite ion, dye chromophoric groups, etc.) to low-valence non-toxic or low-toxic substances. It is a core reducing agent for the treatment of electroplating wastewater and printing and dyeing wastewater. Its reducing performance is mild, the cost is extremely low, and it is suitable for large-scale wastewater treatment scenarios.
     2. 
        
     3. Flocculation and sedimentation: After ferrous ions are oxidized in aqueous solution or react with alkaline substances, they form ferric hydroxide colloid, which has extremely strong adsorption and flocculation capabilities. It can adsorb suspended particles, colloidal impurities, chromatic substances, and heavy metal ions in water bodies, forming dense flocs that settle quickly. This realizes sewage clarification, decolorization, and impurity removal. It is the most commonly used economical flocculant for municipal sewage and industrial wastewater.
     4. 
        
     5. 1. Weak acidity: The aqueous solution is weakly acidic, which can neutralize alkaline wastewater, adjust the pH value of water bodies, and at the same time inhibit the excessive reproduction of algae and bacteria in water bodies, improve the water ecosystem. It is suitable for the pretreatment of alkaline industrial wastewater and municipal sewage, avoiding problems such as pipeline scaling and water quality deterioration caused by excessively high pH values.
     6. 
        
     7. Oxidation sensitivity: Ferrous ions have poor stability. In humid, oxygen-rich, and high-temperature environments, they are easily oxidized to ferric ions by oxygen in the air. The color of the product changes from green to yellowish-brown, and its flocculation and reduction properties decrease significantly. Therefore, during storage and transportation, it is necessary to strictly seal, prevent moisture and sunlight, and the aqueous solution should be prepared and used immediately.
     8. 
        
     9. Chelation stability: Ferrous ions in aqueous solution can undergo a weak chelation reaction with some heavy metal ions in water (such as copper, zinc, lead, etc.) to form stable soluble substances. Combined with the subsequent flocculation process, it can improve the removal effect of heavy metals and is suitable for the treatment of wastewater with multi-metal composite pollution.
     10. 
         
     11. Thermal instability: Ferrous sulfate heptahydrate will quickly lose its crystal water at high temperatures, turning into anhydrous ferrous sulfate. With continued high temperatures, it will decompose into substances such as iron oxide and sulfur dioxide; ferrous sulfate monohydrate has slightly better high-temperature resistance, but it will completely decompose when the temperature exceeds 300°C, losing its industrial use value. Therefore, it is strictly prohibited to store or use it near high-temperature heat sources.
     12. 
         

     13. II. Core Product Characteristics and Performance Advantages of Industrial-grade Solid Ferrous Sulfate

         2.1 Core Usage Characteristics

         The core usage characteristics of industrial-grade solid ferrous sulfate revolve around its four core attributes: strong reducibility, flocculating and precipitating properties, weak acidity, and low cost. Different from similar products such as polyaluminum chloride, polyacrylamide, and sodium bisulfite, it has exclusive industrial adaptation characteristics, covering multiple fields including environmental protection, chemical industry, textiles, metallurgy, agriculture, and building materials. The specific usage characteristics are subdivided as follows:

         2.1.1 Strong Reducing Property: Core Additive for Harmless Treatment of Industrial Toxic Wastewater

         This is the core and most widely used characteristic of industrial-grade solid ferrous sulfate, especially for highly toxic hexavalent chromium-containing wastewater in the electroplating industry. It is the most cost-effective exclusive reducing agent, bar none. Its reduction principle is that ferrous ions (divalent iron ions) reduce highly toxic hexavalent chromium to low-toxic trivalent chromium, which is subsequently removed by precipitation through alkali addition. It boasts high reduction efficiency, with the agent cost being only 1/5 to 1/3 of similar reducing agents, no risk of flammability or explosion, and simple operation. Meanwhile, for oxidative chromophores and high-valence pollutants in printing and dyeing wastewater and chemical wastewater, it can quickly reduce and decolorize, break down the molecular structure of organic pigments, and significantly reduce the chromaticity and COD content of wastewater. It is the preferred agent for the pretreatment of high-chroma industrial wastewater and is suitable for key environmentally regulated enterprises such as electroplating factories, circuit board factories, printing and dyeing factories, and chemical plants.

         2.1.2 High-efficiency flocculation characteristics: Main agent for municipal and industrial sewage purification

         Compared with special flocculants such as polyaluminum chloride and polyferric sulfate, industrial-grade solid ferrous sulfate has mild flocculation performance, dense flocs, fast sedimentation speed, and extremely low cost. It is suitable for large-scale flocculation clarification and sludge dewatering processes in municipal sewage treatment plants and industrial sewage stations. The ferric hydroxide colloid generated by it can not only adsorb suspended impurities in water but also remove some phosphorus elements, heavy metal ions, and chromatic substances, achieving multiple effects of sewage dephosphorization, impurity removal, and clarification. When used in conjunction with polyacrylamide, the sludge dewatering effect is better, which greatly reduces the sludge moisture content and the cost of solid waste treatment. It is an essential agent for the treatment of municipal sewage, domestic sewage, and industrial comprehensive wastewater.

         2.1.3 Acid Adjustment and Alkali Removal Characteristics: Economical Agents for Alkaline Wastewater Neutralization Treatment

         In industrial production, industries such as printing and dyeing, chemical engineering, electroplating, and papermaking often generate a large amount of alkaline wastewater. Direct discharge will destroy the water ecosystem and corrode pipelines. The aqueous solution of industrial-grade solid ferrous sulfate is weakly acidic, which can efficiently neutralize alkaline wastewater and adjust the pH value of the water to neutral or weakly alkaline. Compared with strong acids such as sulfuric acid and hydrochloric acid, the neutralization process is gentler, will not cause a sudden drop in pH value, and has no risk of strong corrosion. At the same time, it has both flocculation and reduction effects, realizing multiple uses of one agent, greatly reducing the cost of wastewater neutralization treatment, and is suitable for the pretreatment of various alkaline industrial wastewater.

         2.1.4 Sludge conditioning characteristics: Special additives for industrial sludge dewatering modification

         The excess sludge produced from municipal sewage and industrial wastewater treatment has high water content, strong fluidity, and is difficult to dewater. Industrial-grade solid ferrous sulfate can be used as a sludge conditioner. It destroys the sludge colloidal structure, neutralizes the negative charges on the sludge surface, makes the sludge particles agglomerate, significantly improves the sludge dewatering performance, reduces the sludge water content, decreases the sludge volume, and facilitates subsequent filter pressing, transportation, and harmless treatment. The conditioning cost is much lower than that of special sludge conditioners, and it is suitable for the sludge dewatering process in various sewage treatment plants.

         2.1.5 Soil Improvement and Iron Supplement Characteristics: Industrial-grade Soil Remediation Additives

         Alkaline soils and salinized soils generally have problems such as iron deficiency, soil compaction, and poor permeability. Industrial-grade solid ferrous sulfate can adjust the soil pH value, improving alkaline soil into weakly acidic soil. At the same time, it supplements iron, an essential element for plant growth, prevents iron-deficiency chlorosis in plants, improves the soil aggregate structure, and enhances soil permeability. It is suitable for scenarios such as landscaping, farmland soil improvement, and industrial contaminated soil remediation, with low cost and long-lasting improvement effects.

         2.1.6 Characteristics of multi-industry general auxiliary materials: multi-functional auxiliary materials for chemical industry, textile industry, building materials industry, and metallurgy industry

         In the field of chemical synthesis, it acts as a reducing agent in various redox reactions to produce chemical products such as iron salts and pigments; in the textile printing and dyeing field, it serves as a fabric mordant and reducing agent to improve fabric dyeing effects and remove impurities on the fabric surface; in the cement industry, it is used as a cement additive to enhance cement strength and shorten setting time; in the metallurgical beneficiation field, it functions as a beneficiation aid to increase the recovery rate of non-ferrous metals and inhibit impurity interference; in the feed industry, it is used as an industrial-grade iron supplement in feed raw material processing (not for direct feeding), with extremely wide application scenarios.

         
         

         

         2.2 Core Performance Advantages (Comparison with Similar Products)

         Comparison Dimension	Industrial-grade solid ferrous sulfate	Polyaluminum Chloride (PAC)	Polyferric Sulfate (PFS)	Sodium bisulfite
         Product cost	Extremely low, with top-tier cost performance in the industry	Medium, relatively high price	On the high side, special flocculant	Medium, dedicated to reducing agents
         Core Functions	Reduction, flocculation, acid adjustment, phosphorus removal, chromium removal	Flocculation, impurity removal, no reducibility	Strong flocculation, phosphorus removal, no reduction function	Strong reduction, dechlorination, no flocculation function
         Storage stability	Just seal it to prevent moisture; no hazardous chemical control is required.	Stable, easily hygroscopic and non-oxidizing	Stable, slightly more corrosive	Strict moisture-proofing required, low-corrosive hazardous chemicals
         Usage safety	Extremely high, non-hazardous chemicals, no risk	High, non-irritating	High, slightly corrosive	Medium, low corrosivity, irritating
         Applicable scenarios	Full-scenario industrial wastewater, multi-industry auxiliary materials	Conventional sewage flocculation	High-standard sewage phosphorus removal flocculation	Wastewater reductive dechlorination and bleaching
         Environmental attributes	Excellent, no secondary pollution, and the products are biodegradable	Excellent, no residue	Excellent, no secondary pollution	Excellent, the product is non-toxic

         III. Specification Parameters and Model Rules for Industrial-grade Solid Ferrous Sulfate

         3.1 Product Model Classification Rules

         There is no unified national standard model naming for industrial-grade solid ferrous sulfate. In the industry, a general model classification rule has been formed by combining the quality grades, core content, physical form, and packaging specifications from the standards GB/T 26637-2011 and HJ/T 291-2006. All models are specifically for the solid form, distinguishing between the two core categories of heptahydrate and monohydrate. The model naming is concise and easy to understand, facilitating procurement selection and production control. The specific classification rules are as follows:

         3.1.1 Classification by Crystalline Water Content and Core Quality (Mainstream Models)

         In the industry, the naming follows the pattern of "initial letter of ferrous + content + category". The core content is calculated based on ferrous iron (Fe²⁺), and it is divided into three grades: superior product, first-class product, and qualified product. This is the most commonly used model classification method:

         
         

         • TY-90 Type (Heptahydrate Superior Product): Ferrous sulfate heptahydrate, with a divalent iron content of ≥90% (corresponding to a FeSO₄·7H₂O content of ≥98%), extremely low impurity content, suitable for high-standard electroplating wastewater treatment, chemical synthesis, and precision environmental protection projects.
         • 
           

         • TY-85 Type (Heptahydrate First-Class Product): Ferrous sulfate heptahydrate, with a divalent iron content of ≥85% (corresponding to a FeSO₄·7H₂O content of ≥92%), moderate impurity content, suitable for general scenarios such as municipal sewage, ordinary printing and dyeing wastewater, and sludge dewatering;
         • 
           
         • TY-80 Type (Heptahydrate Qualified Product): Ferrous sulfate heptahydrate, with a divalent iron content of ≥80% (corresponding to a FeSO₄·7H₂O content of ≥87%), impurity content meeting the minimum requirements of national standards, suitable for non-precision scenarios such as soil improvement, neutralization of ordinary alkaline wastewater, and cement addition.
         • 
           
         • YS-98 Type (Monohydrate Premium Product): Ferrous sulfate monohydrate, with a divalent iron content of ≥98% (corresponding to a FeSO₄·H₂O content of ≥99%), high purity, low impurity, suitable for high-end sewage treatment, feed industry, and chemical synthesis.
         • 
           
         • YS-95 Type (Monohydrate First-Class Product): Ferrous sulfate monohydrate, with a divalent iron content of ≥95% (corresponding to a FeSO₄·H₂O content of ≥96%), suitable for scenarios such as large-scale sewage treatment plants, automated feeding, and long-distance transportation.

         • 3.1.2 Classification by Physical Form and Particle Size

           • TY-K Type (Heptahydrate Granular Type): Particle size 0.5-2.0mm, light green crystalline granules, dust-free, good fluidity, mainstream general-purpose type on the market.
           • 
             
           • TY-M Type (Heptahydrate Powder Type): Particle size ≤ 0.5mm, light green powder, fast dissolving, suitable for small sewage stations and precise dosing;
           • 
             
           • YS-K Type (Monohydrate Granular Type): Particle size 0.3-1.0mm, grayish-white granules, dust-free, non-caking, high-end special-purpose type.
           • 
             
           • YS-M Type (Monohydrate Powder Type): Particle size ≤ 0.3mm, grayish-white ultra-fine powder, high purity, fast dissolving, specially used for precision scenarios.

           • 3.1.3 Classification by Packaging Specifications

             • Small packaging type: 5kg/bag, 10kg/bag, suitable for laboratory small-scale tests and small-batch production trials;
             • 
               
             • Regular packaging type: 25kg/bag, 50kg/bag, suitable for the regular production of small and medium-sized enterprises, and is the main product in the market circulation;
             • 
               
             • Large packaging ton bag type: 1000kg/ton bag, suitable for large sewage treatment plants, large-scale production, and bulk procurement.
             • 
               
             • 

             • 3.2 Core Specification Parameters (Full National Standard Indicators)

               3.2.1 Parameters of Ferrous Sulfate Heptahydrate (HJ/T 291-2006)

               Indicator Items	Superior product	First-class product	Qualified product	Detection Method
               FeSO₄·7H₂O ≥%	98.0	92.0	87.0	Potassium permanganate titration method
               Fe²⁺ ≥%	90.0	85.0	80.0	Potassium permanganate titration method
               Water insoluble matter ≤%	0.2	0.5	1.0	Gravimetric method
               Arsenic (As) ≤%	0.0001	0.0002	0.0003	Arsenic spot method
               Lead (Pb) ≤%	0.001	0.002	0.005	Atomic absorption spectrophotometry
               pH value（50g/L）	3.5-4.5	3.5-4.5	3.5-4.5	pH meter determination

               3.2.2 Parameters of Ferrous Sulfate Monohydrate (GB/T 26637-2011)

               Index Items	Premium grade	First-class product	Qualified product	Detection method
               FeSO₄·H₂O ≥%	99.0	96.0	92.0	Potassium permanganate titration method
               Fe²⁺ ≥%	98.0	95.0	90.0	Potassium permanganate titration method
               Water-insoluble matter ≤%	0.05	0.1	0.2	Gravimetric method
               Arsenic (As) ≤%	0.0001	0.0002	0.0003	Arsenic spot method
               Lead (Pb) ≤%	0.001	0.002	0.005	Atomic Absorption Spectrophotometry
               pH value (50g/L）	3.0-4.0	3.0-4.0	3.0-4.0	pH meter determination

               3.3 Packaging and Storage/Transportation Parameters

               3.3.1 Packaging Specifications

               • Material: Outer layer is polypropylene woven bag/kraft paper bag, inner layer is high-density polyethylene moisture-proof inner membrane, with double-layer sealing.
               • 
                 
               • Sealing: The inner membrane is heat-sealed, and the outer bag is sewn with double threads to prevent air leakage and moisture.
               • 
                 
               • Marking: The bag body clearly prints the product name, model, content, grade, execution standard, production date, shelf life, storage and transportation warnings, and manufacturer information;
               • 
                 
               • Dimensions: 25kg bag 55cm × 35cm, 50kg bag 65cm × 45cm, ton bag 90cm × 90cm × 110cm.
               • 
                 
               • 
               • 
                 

               • 3.3.2 Storage and Transportation Requirements

                 • Storage: Store in a cool, dry, and well-ventilated warehouse with a temperature ≤30℃ and humidity ≤65%. Keep away from direct sunlight, high-temperature heat sources, strong acids, and oxidants. The stacking height should be ≤8 layers, the distance between stacks ≥30cm, and the distance from the wall ≥50cm;
                 • 
                   
                 • Transportation: Transport by box trucks/covered trucks, ensuring protection against rain, moisture, and sunlight. Open-air bulk transportation is strictly prohibited. It is a non-hazardous chemical, and regular freight qualifications are sufficient.
                 • 
                   
                 • Shelf life: When stored in a well-sealed condition, ferrous sulfate heptahydrate has a shelf life of 6-8 months, and ferrous sulfate monohydrate has a shelf life of 12 months. Use as soon as possible after opening.

                 • IV. Grading Quality Standards for Industrial-grade Solid Ferrous Sulfate

                   4.1 Implementation Standards and Compliance Basis

                   The product quality strictly complies with two current national standards and also meets the relevant specifications for the production and environmentally friendly use of chemical products:

                   
                   

                   • GB/T 26637-2011 "Industrial Ferrous Sulfate" (General Standard for Industrial Production);
                   • 
                     
                   • HJ/T 291-2006 "Water Treatment Agent - Ferrous Sulfate" (Special Standard for Water Treatment);
                   • 
                     
                   • GB/T 8946-2013 "General Technical Requirements for Plastic Woven Bags" (Packaging Standard);
                   • 
                     
                   • Law of the People's Republic of China on the Prevention and Control of Environmental Pollution by Solid Wastes (Compliance of Waste Disposal);

                   • 4.2 Grading Quality Judgment Rules

                     The principles of full-item compliance determination and one-vote veto shall be implemented. If any indicator fails to meet the standard, the product shall be downgraded or judged as unqualified, and it is strictly prohibited to leave the factory for use.

                     4.2.1 Determination of Premium Grade Products

                     The main content and divalent iron content meet the standards; the contents of impurities such as water-insoluble substances, arsenic, and lead are ≤ the upper limit of premium grade products; the appearance is uniform without impurities or oxidized agglomerates; the pH value and water solubility meet the standards; the packaging is intact and the labels are complete.

                     4.2.2 Determination of First-Class Products

                     The main content and divalent iron content meet the standards; the impurity content is ≤ the upper limit of first-class products; the appearance has no obvious impurities, and slight oxidation does not affect use; the water solubility is good; and the packaging is intact.

                     4.2.3 Qualified Product Determination

                     The main content and divalent iron content are ≥ the minimum value of the national standard, the impurity content is ≤ the upper limit of qualified products, there is no severe oxidation and agglomeration, no foreign mechanical impurities, and it meets the requirements for use in basic industries.

                     4.2.4 Unqualified Product Determination

                     A product is deemed unqualified if any of the following circumstances occur: the main content is lower than the minimum value specified in the national standard; toxic impurities such as arsenic and lead exceed the standard; there is severe oxidation, agglomeration, discoloration, or deterioration; the aqueous solution is difficult to dissolve, turbid, or has hard precipitates; the packaging is damaged, labels are missing, or there is moisture absorption and leakage.

                     4.3 Quality Inspection and Control Process

                     4.3.1 Raw Material Control

                     All incoming production raw materials (iron powder, sulfuric acid, pure water) undergo a full range of inspections. Only when their purity and impurity levels meet the standards can they be put into production. Samples and inspection reports are retained for 6 months.

                     4.3.2 In-process Sampling Inspection

                     In the production process, sampling inspection is conducted every 2 hours to test the content, moisture, and appearance. The process is adjusted in real-time to ensure the stability of product quality.

                     4.3.3 Full Inspection of Finished Products Before Factory Delivery

                     After the finished products are packaged, a full range of inspections are conducted in accordance with national standards. Qualified products will have a quality inspection report issued, which will accompany the goods. Unqualified products are stored separately and are strictly prohibited from entering the market.

                     4.3.4 Third-Party Re-inspection

                     In high-standard scenarios, re-inspection can be entrusted to third-party authoritative institutions (such as Quality Inspection Institutes, SGS, etc.). Both the supplier and the demander shall jointly seal the samples, and the re-inspection result shall be the final basis for judgment.

                     4.4 Handling of Quality Objections

                     If the purchaser has any objections to the quality, they must submit a written statement within 7 days of receiving the goods, provide samples and proof of receipt. Both parties shall jointly entrust a third party for testing. If the test result is qualified, the testing fee shall be borne by the purchaser; if unqualified, the fee shall be borne by the supplier, and the supplier shall unconditionally accept returns and exchanges.

                     
                     

                     

                     V. Safe Operation, Emergency Disposal and Waste Treatment

                     5.1 Safety Operation Precautions

                     • Operators shall wear dust masks, rubber gloves, goggles, and work clothes to avoid direct contact with the skin and eyes. Eating and smoking at the work site are strictly prohibited;
                     • 
                       
                     • When feeding materials, handle them gently to avoid dust from flying. When preparing the solution, slowly add the product to water while stirring continuously. It is strictly prohibited to add water to the product;
                     • 
                       
                     • The workplace should be kept ventilated, equipped with clean water sources and eye washers, and long-term inhalation of dust should be avoided;
                     • 
                       
                     • It is strictly prohibited to store or transport together with strong acids, strong alkalis, oxidants, food, and feed.

                     5.2 Emergency Response Measures

                     • Skin contact: Immediately remove contaminated clothing, rinse with plenty of water for more than 15 minutes, and seek medical attention if feeling unwell.
                     • 
                       
                     • Eye contact: Immediately lift the eyelids, rinse with plenty of clean water or physiological saline for more than 15 minutes, and seek medical treatment;
                     • 
                       
                     • Inhalation: Move to a place with fresh air, keep the respiratory tract unobstructed, and seek medical attention if having difficulty breathing;
                     • 
                       
                     • Accidental ingestion: Immediately drink plenty of warm water or milk, do not induce vomiting, and seek medical attention promptly.
                     • 
                       
                     • Leakage: Wear protective equipment, absorb with dry sand, collect into a sealed container, dispose of as industrial solid waste, and avoid flowing into water bodies.

                     5.3 Waste Disposal Specifications

                     Expired and deteriorated products belong to general industrial solid waste and shall be handed over to qualified units for harmless treatment; waste packaging bags shall be recycled after cleaning or handed over to professional units for disposal; waste solutions shall be adjusted to neutral pH and then discharged in accordance with industrial wastewater standards, and random dumping is strictly prohibited.

                     VI. Common Problems and Solutions

                     • Product caking: The causes are moisture absorption and poor sealing. Slightly caked products can be used normally after being crushed; severely caked products can be used at a reduced grade after testing their content. To prevent caking, the product should be stored in a sealed and moisture-proof manner.
                     • 
                       
                     • Oxidative discoloration: The causes are exposure to air and high temperatures, which lead to yellowing of color and deterioration of performance. It can be used in non-precision scenarios such as soil improvement. To prevent it, avoid light, keep it sealed, and store it in a cool place.
                     • 
                       
                     • Poor flocculation effect: The causes are insufficient content, insufficient dosage, and inappropriate pH. Adjust the dosage and pH value, and replace with qualified products.
                     • 
                       
                     • Slow dissolution: The causes are caking, poor water quality, and broken products. Dissolve with clean water and stir thoroughly.

                     Conclusion

                     Industrial-grade solid ferrous sulfate, as an economical and multifunctional industrial additive, plays an irreplaceable role in industrial environmental protection, process production, soil improvement and other fields by virtue of its core advantages of multiple properties, low cost, safety and convenience. This manual comprehensively covers the core information of the product, strictly follows national standards, takes both professionalism and practicality into account, and is accompanied by complete graphic display guidelines, which can provide all-round guidance for users in procurement and selection, on-site use, quality acceptance, storage and transportation control. In actual use, it is necessary to select the corresponding grade of products according to specific scenarios and strictly implement the operation and storage specifications, which can not only maximize the product efficacy, but also effectively avoid safety and quality risks, helping industrial production reduce costs, increase efficiency and meet environmental protection standards.