Polyaluminium Chloride, often recognized by the abbreviation PAC, works as a chemical coagulant with a broad footprint across water treatment and various industrial processes. The substance appears in several forms, including powders, granules, flakes, pearls, and liquid concentrations. The core element in PAC's efficiency comes from its complex polymeric structure, which taps into both aluminum and chloride ions. As an environmental engineer, I have watched PAC dethrone older coagulants—like aluminum sulfate—due to its better performance and straightforward dosing. This chemical sits with the HS Code 28273200, placing it within the group of inorganic chemicals used for surface and ground water purification or as a paper industry additive. Its molecular formula reads Aln(OH)mCl3n−m, meaning the ratios shift based on manufacturing method and final application. Density plays a key role in its handling and application: powders reach nearly 1.15-1.20 g/cm3, while liquid suspensions push close to 1.3 g/cm3.
Polyaluminium Chloride stands out for its strong coagulation power, and it acts quickly in clarifying water. Its performance can be traced to its high positive charge, making it far more potent at destabilizing suspended particles compared to simple alum or ferric salts. This property also means using less of it to achieve the same cleanliness, which matters deeply in real-world operations where cost and efficiency mean survival for many water plants. PAC’s solubility remains high in water, so it dissolves fast when blended as either a concentrated solution or as a powder poured straight into a dosing tank. In practical settings, I have witnessed PAC cut sludge generation downstream of the purification process, easing both disposal headaches and environmental reporting. Crystalline forms and pearls offer slower dissolution, which works well in big batch reactors or in places needing a long release rate.
The internal structure of PAC relies on a web of aluminum hydroxyl and chloride complexes. Each manufacturer tailors the blend slightly, affecting everything from basicity (the ratio of hydroxyl to aluminum ions) to the final pH impact during use. Low-basicity PAC finds use in pools and textile work, where delicate balance of ions means no room for error; higher-basicity compounds tackle municipal water full of organic material or cloudy rivers. Solutions can range in active content—typical liquid PAC runs at 10-18% Al2O3 by mass, while solid powders rise as high as 30%. Effective dosing rides on tight control of these specifications, so trusted suppliers always share batch certificates showing values for pH, basicity, water insolubles, and iron content. Good quality PAC keeps iron and heavy metals well below drinking water safety limits.
PAC enters the market as pale yellow to deep yellow powders, brittle flakes, crystalline pearls, and concentrated aqueous solutions. Powdered PAC tends to work best for easy transportation and long-term storage—no caking, less moisture uptake, and a shelf life pushing past two years if containers stay sealed and dry. In hotter climates or sites dependent on rapid solubilization, flakes and pearls win out because they avoid airborne dust and dissolve more gradually. Liquid PAC brings a speedy solution to continuous dosing rigs, favored at large waterworks and paper mills, but it asks for corrosion-proof tankage and careful monitoring to avoid algal growth during weeks of summer heat. All forms demand secure storage away from strong acids, alkalis, and reactive metals. No one in the field enjoys cleaning up a chemical spill, and PAC’s high chloride load can mean corrosion in pumps or fittings if leaks go unnoticed.
Densities swing depending on the PAC’s concentration and form. Solid forms pack as dense powders or brittle fragments, typically hovering around 1.15 to 1.20 g/cm3. Liquid PAC presents with densities in the 1.2-1.3 g/cm3 range, varying by the percent of active Al2O3. Accurate dosing relies on knowing these figures—a mistake here risks underdosing or overdosing, impacting operating costs and quality. Most solid PAC arrives in double-layer plastic woven sacks, weighing in at 25 kg per bag for safe manual handling; liquid PAC often ships in 1,000-liter IBC tanks or smaller drums for sites using small batches. Shelf life stretches long if conditions stay cool and dry, but the minute humidity creeps in, cake formation and loss of activity become real threats. Keeping bags off warehouse floors and away from direct heat reduces losses in storage.
Manufacturing PAC calls for aluminum hydroxide, hydrochloric acid, and water as the core raw materials. The recipe brings these together under controlled temperatures to yield the finished product, with extra attention on purification. Impurities like iron, heavy metals, or residual organics can cause big troubles once the final product enters municipal water lines or food-contact industries. Handling PAC goes smoothly if the right gear gets used: gloves, goggles, and a dust mask work for powders and flakes; eye and skin protection plus spill containment pans help with liquid drums. In my time on plant floors, I have watched complacency lead to mild chemical burns or corrosion patches on stainless steel pipes where minor leaks went unreported for months. PAC irritates skin, eyes, and mucous membranes—nobody likes a splash to the face—so working under local chemical safety rules is non-negotiable. Proper ventilation, steady training, and keeping a clean-up kit nearby stand as easy ways to stay ahead. Storage away from acids, food, or animal feed avoids contamination risks.
PAC draws its hazard profile mostly from its corrosiveness at high concentrations and potential for aluminum exposure if misapplied or overdosed. The risk rises in poorly-ventilated rooms or from uncontrolled powder handling, where inhalation may lead to coughing and minor inflammation. Spilled product, if not swept up at once, attracts moisture and cakes fast, which invites slip hazards and tracking outside containment zones. Some older reports have raised concerns about long-term aluminum exposure via drinking water, though frequent regulatory reviews keep PAC within strict use limits for potable water plants. It stands as non-flammable and not reactive under normal use, so its main threat comes from negligence or improper handling. In environmental terms, PAC proves less harmful than older coagulants since it keeps dose rates low, reduces residuals post-treatment, and avoids adding large quantities of sulfate or iron to finished water. Any leftover from treatment processes must be responsibly collected and disposed of, following local hazardous waste protocols.
Experience in both industrial and municipal treatment sites shows PAC helps streamline water purification, trim chemical use, and cut long-term waste. Each form—powder, flakes, pearls, crystal, and liquid—serves a unique setting, but every operator must take storage, handling, and dosing seriously. Working directly with measurable properties like density, solubility, and purity can prevent both health risks and costly process errors. Safe, responsible use always rides above convenience. By respecting the chemical's strengths , people keep their teams healthy, their factories running, and their products or communities safe.
