Aluminium Potassium Sulfate Formula vs. Potassium Sulfate: A Comprehensive Guide for Industrial Buyers
The aluminium potassium sulfate formula often surfaces when procurement managers first explore potassium-based industrial chemicals. However, aluminium potassium sulfate (commonly called potash alum) and potassium sulfate (K2SO4) are two entirely different substances with distinct chemical structures, applications, and market dynamics. At Hailei Chemical, we regularly help buyers clarify this distinction—especially those seeking a premium, chlorine-free potassium source for fertilizers, glass manufacturing, or pharmaceutical production. In this deep-dive article, we’ll unpack the aluminium potassium sulfate formula, compare it with pure potassium sulfate, and equip you with the technical and commercial knowledge to make a confident purchasing decision.
What Is Aluminium Potassium Sulfate? Decoding the Formula
The aluminium potassium sulfate formula is KAl(SO4)2·12H2O, representing a hydrated double sulfate of aluminium and potassium. It crystallizes as a dodecahydrate, meaning each formula unit incorporates twelve water molecules. This chemical is widely known as potash alum, potassium alum, or simply alum. Industrially, it is produced by combining aluminum hydroxide with sulfuric acid and potassium sulfate, then crystallizing the product.
Its key characteristics include a molecular weight of 474.39 g/mol (as the dodecahydrate), excellent water solubility, and an acidic pH in solution. The aluminium content (as Al2O3) is typically around 10.7%, and the potassium (as K2O) is approximately 9.9%. However, because of the high water of crystallization, the effective potassium concentration is much lower than that of dedicated potassium fertilizers like potassium sulfate (K2SO4).
The aluminium potassium sulfate formula finds principal use in water treatment as a flocculant, in papermaking as a sizing agent, in dyeing as a mordant, and in certain food applications (E number E522). While it does supply potassium, its aluminium component can be phytotoxic to sensitive crops, making it unsuitable for direct agricultural potassium fertilization.
What Is Potassium Sulfate (K2SO4) Fertilizer?
Potassium sulfate, or sulfate of potash (SOP), has the simple chemical formula K2SO4. Unlike the aluminium potassium sulfate formula which contains aluminium and crystallized water, pure potassium sulfate delivers only potassium and sulfur—two essential plant macronutrients—without chlorine, nitrogen, or heavy metals.
Commercial-grade potassium sulfate for agriculture typically guarantees a minimum 50% K2O (equivalent to ~41.5% K) and 18% sulfur. For technical- and pharmaceutical-grade premium chlorine-free potassium sulfate, purity exceeds 99%, with heavy metal residues controlled below 5 ppm. It is produced via the Mannheim process (reacting potassium chloride with sulfuric acid at high temperatures) or from natural brine sources such as the Great Salt Lake in the USA and the Lop Nur region in China.
Because it contains no chlorides, SOP is the fertilizer of choice for chloride-sensitive high-value crops: tobacco, potatoes, grapes, citrus, avocados, and many vegetables. Its low salt index minimizes osmotic stress, making it safer for delicate root systems.
Aluminium Potassium Sulfate vs. Potassium Sulfate: Key Differences at a Glance
For procurement professionals, comparing the aluminium potassium sulfate formula with K2SO4 is essential. The table below highlights the critical divergences.
| Parameter | Aluminium Potassium Sulfate (Alum) | Potassium Sulfate (SOP) |
|---|---|---|
| Chemical formula | KAl(SO4)2·12H2O | K2SO4 |
| K2O content | ~9.9% (hydrated basis) | ≥50% |
| Sulfur content | ~13% | ~18% |
| Aluminium content | ~10.7% as Al2O3 | None |
| Primary uses | Water treatment, paper, dyeing | Fertilizer, glass, pharma, alum recycling |
| Suitability for crops | Not recommended (phytotoxic Al) | Ideal for chloride-sensitive crops |
| Typical bulk price | $250–$400/MT | $600–$900/MT (agricultural grade); higher for pharma |
| CAS number | 7784-24-9 | 7778-80-5 |
How Is Potassium Supplied? The Potassium Supply Chain Explained
When asking “how is potassium supplied” to global markets, one must understand that potassium—the seventh most abundant element in the earth’s crust—is primarily produced in the form of potash salts. The main ores are sylvite (KCl), sylvinite (KCl·NaCl), langbeinite (K2SO4·2MgSO4), and carnallite (KCl·MgCl2·6H2O).
Potassium chloride (MOP) dominates global potash production (over 95%), but its high chloride content limits its use in salt-sensitive agriculture. Sulfate of potash (K2SO4) is produced mainly through three routes:
- Mannheim process: Reaction of KCl with H2SO4 in a high-temperature furnace, yielding SOP and hydrochloric acid. This method accounts for ~50% of global SOP capacity and delivers a high-purity (>50% K2O) product ideal for soluble fertilizer blends.
- Natural brine processing: Solar evaporation and selective crystallization from saline lakes produce SOP with a smaller carbon footprint. China’s Lop Nur basin and Chile’s Atacama are key sources.
- Langbeinite processing: The mineral langbeinite (K2Mg2(SO4)3) is crushed and screened to produce K-Mag, a low-chloride potassium magnesium sulfate product.
At Hailei Chemical, we source potassium sulfate from state-of-the-art Mannheim facilities, ensuring consistent quality with K2O content never below 50% and chloride <1%. Bulk shipments are available in 25 kg, 50 kg, 1000 kg big bags, and loose bulk.
Understanding the Price Potassium Sulfate Market and Key Factors
Procurement managers frequently search “price potassium sulfate” to benchmark budgets. As of early 2025, agricultural-grade SOP FOB China ranges from $600 to $850 per metric tonne, while pharmaceutical/food-grade SOP commands a premium of $900–$1,200 per metric tonne. Several variables determine the final price potassium sulfate buyers pay:
- Feedstock costs: Potassium chloride (MOP) and sulfuric acid are the main raw materials. MOP prices (typically $300–$400/MT) directly influence SOP production economics.
- Energy: The Mannheim process is energy-intensive, so natural gas and electricity prices significantly impact manufacturing costs.
- Purity requirements: Technical grades (99%+ purity) for glass or pharma require additional refining, filtration, and testing, adding $100–$200/MT.
- Logistics: SOP is often shipped in containers or bulk vessels. Ocean freight rates from China to Latin America or Europe can swing by 30% within a quarter, affecting delivered price.
- Seasonality: Pre-planting fertilizer demand spikes (Q4–Q1) often firm prices.
When comparing quotes, always confirm whether the price is FOB, CIF, or delivered duty paid (DDP), and verify the K2O guarantee, moisture content (typically <0.5%), and particle size distribution. Our potassium sulfate product page provides detailed technical specifications to support your budgeting.
Aluminum Potassium Sulfate SDS and the Safety Profile of Potassium Sulfate
While the aluminum potassium sulfate SDS lists hazards related to aluminium sulfate (irritant, possible respiratory sensitizer), potassium sulfate (K2SO4) is notably different. According to the Safety Data Sheet for typical potassium sulfate, it is not classified as hazardous under GHS. It is a white crystalline powder with low acute oral toxicity (LD50 oral rat > 2000 mg/kg) and no significant ecotoxicity.
However, standard industrial hygiene applies: avoid dust generation, use mechanical ventilation, and wear protective gloves and safety glasses. In manufacturing environments, any spillage should be swept up to prevent slip hazards. Unlike alum, potassium sulfate does not release aluminium ions, making it safer for agrochemical blending and pharmaceutical use.
For buyers requiring an aluminum potassium sulfate SDS for their alum-based processes, it’s critical to understand that the same safety considerations do not carry over when procuring potassium sulfate. Request the specific SDS from your supplier—our commercial team provides up-to-date documentation compliant with REACH, EC 1907/2006, and other regional regulations.
High-Value Agricultural Use: What Is Potassium Sulfate Fertilizer, and Why Does Chlorine-Free Matter?
This section answers the common search “what is potassium sulfate fertilizer” while underscoring its role in modern agriculture. Potassium sulfate fertilizer is a water-soluble potassium source containing no nitrogen or phosphorus, allowing growers to precisely manage K nutrition without altering nitrogen schedules. The sulfate sulfur (SO4-S) it provides is immediately plant-available, unlike elemental sulfur which must be oxidized by soil bacteria.
Chloride toxicity causes leaf margin burn, reduced fruit quality, and lower starch content in tubers. Crops such as tobacco, where chloride can reduce leaf burn quality, and grapes, where excess salt can stunt vine growth, demand K2SO4. In high-tunnel vegetable production, SOP’s low salt index helps maintain soil electrical conductivity within safe limits.
Agronomic field trials consistently show that SOP-applied potato crops achieve higher dry matter content and better storage quality than those fertilized with MOP. For avocado and citrus, SOP applications improve fruit size and oil content. Hailei Chemical’s SOP dissolves quickly, making it ideal for fertigation systems and foliar sprays after appropriate filtration.
Industrial Applications Beyond Agriculture: Glass, Aluminum Recycling, and Pharma
Beyond its agricultural value, potassium sulfate is indispensable in several industrial segments where the aluminium potassium sulfate formula cannot substitute because of aluminium cross-contamination.
Glass Manufacturing
In specialty glass production, potassium sulfate serves as a refining agent. It lowers the melt viscosity, helping to release bubbles and create a homogeneous glass matrix. The potassium ion imparts a higher thermal expansion coefficient, crucial for glass-to-metal seals in electronic packaging. Optical glasses also benefit from potassium’s ability to increase refractive index. Our SOP grade for glass guarantees sulphate purity >99.2% and minimal iron content (<5 ppm Fe2O3) to prevent unwanted coloration.
Aluminum Recycling
Secondary aluminum smelters use potassium sulfate as a fluxing salt in rotary furnaces. Under the salt flux cover, K2SO4 reduces metal oxidation, absorbs non-metallic impurities, and improves the recovery rate of aluminum. The chlorine-free nature of SOP is critical here—chlorine-containing fluxes can release corrosive HCl gas. Hailei Chemical supplies a customized granulated (0.2–2 mm) SOP to smelters, ensuring optimal dispersion and melting behavior.
Pharmaceutical Excipient
Pharmaceutical-grade potassium sulfate meets USP-NF, EP, and JP monographs. It is used in tablet formulations, dialysis solutions, and as a source of potassium and sulfate ions in parenteral nutrition. The manufacturing process at our facility operates under strict GMP, with a dedicated clean room packaging line. Aluminium, arsenic, and lead limits are monitored batch-wise, and we provide full certificates of analysis.
Gypsum Board Additive
In gypsum wallboard production, a small addition of potassium sulfate accelerates the setting time of stucco (calcium sulfate hemihydrate). The sulfate ions promote nucleation of gypsum crystals, increasing production line speed. Our fine powder SOP (<100 µm) blends evenly and complies with ASTM C1396 requirements for wallboard additives.
Sourcing Premium Potassium Sulfate: Why Hailei Chemical Stands Out
With hundreds of suppliers worldwide, industrial buyers must evaluate reliability, certification, and logistics capability. Hailei Chemical has exported K2SO4 to over 30 countries for more than a decade. We offer:
- Vertically integrated production: We control the full Mannheim line, ensuring stable cost and consistent quality.
- Multiple grades: Agricultural, industrial, and pharmaceutical grade—all from one source, simplifying vendor qualification.
- Customization: Particle size grinding, anti-caking treatment, and private labeling possibilities.
- Regulatory compliance: Our products are pre-registered with REACH, and we supply SDS, COA, and phytosanitary certificates as needed.
- Reliable logistics: Direct loading in Qingdao port with 15–25 day vessel transit to major destinations.
Don’t settle for a generic potassium source that may compromise your process. Whether you need K2SO4 for a sensitive vineyard, a medical device, or an aluminum smelter, contact us today for a competitive CIF or DDP quotation.
Ready to secure a consistent supply of high-purity potassium sulfate? Request your personalized quote now and discover why leading importers trust Hailei Chemical.