How Does Polyaluminum Chloride Work

If you've ever seen dirty water get clear after some treatment, polyaluminum chloride, or PAC, was likely the main player working hard in the background. It's one of those smart chemical helpers that help make clean water happen in places like city water stations and paper factories. But how does this stuff really do its job? 

PAC stands as a key coagulant in water cleaning for towns and factories. It gets the work done well, fits different needs, and saves money in the long run. Before we get into how it works, it's good to note that companies such as Hainan Horizon Import and Export Co., Ltd. have led the way in making and shipping top-notch PAC and other water cleaning chemicals for many years. With over 30 years of know-how, Horizon's factories put out hundreds of thousands of tons of solid and liquid water treatment stuff each year. They supply projects in more than 30 countries around the world.

Their skills go beyond just big numbers. It's about getting things just right. Each batch gets checked for things like alumina amount, pH level, and dirt traces. This makes sure everything stays steady and dependable, which is what engineers count on day after day. 

What Is Polyaluminum Chloride?

Polyaluminum chloride is a kind of inorganic polymer coagulant. It comes from a careful process of breaking down aluminum salts through hydrolysis. In chemical terms, it's usually written as Al₂(OH)ₙCl₆₋ₙ. That formula shows it has lots of positive charges. These charges pull in and stick to negatively charged bits in the water. Put simply, PAC works like a magnet for grime and floating solids.

It shows up as a light yellow powder or a see-through liquid. The exact shade and feel often tell you about its quality and cleanliness. For example, Industrial Grade Polyaluminium Chloride tends to look a bit darker. People use it for cleaning waste water in spots like paper mills, cloth factories, or mining sites. On the other hand, Drinking Water Grade Polyaluminium Chloride is much lighter. It follows country rules like GB15892-2020 for water you can drink.

Both kinds get made with modern spray-drying methods. This gives them small grains, good mixing in water, and solid results over a broad set of pH levels. PAC steps in, grabs those bits, and pulls them out fast. In one case from a textile plant in southern China, workers switched to this grade and saw the water clear up in half the time compared to before. That's the kind of practical win that keeps it popular.

How Does PAC Work in Water Treatment?

When PAC hits the water, a bunch of reactions start up right away. It's not only about the science. Timing and a touch of skill play a part too.

Step 1: Hydrolysis Reaction

Right after you add it, PAC breaks down through hydrolysis. This happens super quick. It forms positive aluminum pieces like Al(OH)²⁺ and Al₂(OH)₂⁴⁺. These are the main workers that will link up with junk later on. The whole thing depends on warmth and pH a lot. PAC does its best job in the range of 5 to 9. 

Step 2: Charge Neutralization

A lot of the bad stuff in water, such as clay bits, mud, or plant scraps, has negative charges on their outsides. That's what keeps them floating apart. They push each other away. The positive aluminum groups from PAC cancel out those negative charges. This stops the pushing. Now the particles can get close without a fight. In a real setup, like at a small town filtration plant, operators notice the water stops looking so cloudy almost as soon as they mix it in. It's a small but satisfying shift.

Step 3: Adsorption and Bridging

Once the charges balance out, the OH groups in PAC begin to connect the particles. These are big clumps you can see with your eyes. They drop down easy. Sometimes, if the water has extra oils from machinery runoff, the bridging takes a tad longer. But with a quick stir, it all comes together. One engineer from a Midwest U.S. mill shared how they adjusted the mix speed here, and flocs formed twice as fast.

Step 4: Floc Formation and Sedimentation

In the last part, the flocs keep growing. They get thicker and sink to the bottom. What you end up with is water that's much clearer. And it makes way less gunk at the bottom than with old alum. Places that change over to PAC say they cut water cleaning costs by 15 to 30 percent. Plus, things settle quicker. Take a paper factory in Europe. They used to deal with thick sludge piles every week. After PAC, those piles shrank, and cleanup took half the crew time.

What Factors Affect PAC Performance?

Even a solid coagulant like PAC can go wrong if the setup isn't spot on. 

Water Quality

The makeup of the starting water counts a ton. Lots of cloudiness can help the clumps form better. But too much plant junk or greasy stuff might call for extra PAC. Or even a helper chemical. In river water fed to city plants, seasonal algae blooms throw things off. Back in 2022, one facility near the Great Lakes upped their dose by 20 percent during a bad bloom. That kept everything running smooth.

pH Range

PAC handles changes better than most old coagulants. Still, it likes things neutral or a smidge basic. If the pH gets too low, the aluminum shapes change. And that cuts down on how well it works. Lab tests show a drop from 7 to 4 can halve the floc size. So, operators check meters often, especially after rain that acidifies runoff.

Dosage

Piling on more PAC isn't always the fix. A small amount might miss some charges. Too much can make particles push apart again. Most teams do a jar test first. It's like a mini trial in glass jars. They shake, watch, and pick the right scoop for that day's water. In practice, doses run from 10 to 50 mg per liter, depending on the mess level.

Mixing and Stirring

After you put it in, fast mixing spreads it even. Then slow stirring lets the clumps build without smashing. The usual steps are quick blend, easy swirl, and let it sit to settle. Skip the fast part, and you get uneven spots. 

Temperature and Storage

Cool water makes the breakdown and clump growth drag. In winter, you might need a bigger dose. Say 10 to 15 percent more in freezing temps. For keeping PAC, store it shut tight and dry. Keep it out of the sun. Liquid kinds might split a bit over time. Just give it a quick shake, and it's good. Oh, and don't stack bags too high in a humid shed. Moisture sneaks in and ruins batches faster than you'd think.

For steady results over time, outfits like Hainan Horizon Import and Export Co., Ltd. watch every load close. They test for alumina at least 29 percent, pH from 3.5 to 5.0, and iron under 0.2 percent. These checks aren't just checkboxes. They tie straight to how well flocs hold and how clean the final water turns out.

What Should You Keep in Mind When Using PAC?

Picking PAC is just the start. The real trick is using it right for steady outcomes.

Start by tweaking the amount based on the water type and time of year. Next, keep it in a cool, dry spot. Sealed bags or drums stop water from soaking in. Powder lasts about 12 months that way. Liquid ones? Use them in 6 to 9 months to stay sharp.

Safety matters a bunch. PAC isn't as harsh as some tougher chemicals. But it can still sting skin or eyes. Wear gloves and glasses as basics. Especially when mixing strong batches. Big setups often use auto-feeders now. These keep workers safe and hit the mark on amounts every time.

You can grab full tips on handling and tech sheets on the manufacturer's resource page. Plus, there are stories from real jobs, like cleaning petrochemical waste or making paper whiter. One standout was a brewery in Australia. They used PAC to handle beer rinse water loaded with yeast bits. Flocs dropped clean, and they saved on filter changes.

Why Choose PAC for Your Water System?

PAC's all-around usefulness is why so many go for it. It handles drinking water and factory runoff alike. It deals with big swings in pH and heat without fuss. And it leaves behind less mess to haul away. Pair it with a few easy changes in your setup, and you trim down running costs plus fix-up troubles.

If you're after dependable supplies, Hainan Horizon Import and Export Co., Ltd. gives hands-on help, custom mixes, and shipping worldwide. Their style isn't only about moving product. It's about handing over a full plan for clean water, backed by facts, checks, and what works in the field. Consider a mining operation in Africa. They faced muddy tailings water that clogged pipes yearly. PAC cleared it up, cut downtime, and even helped local streams recover a bit. Small wins like that make the choice feel right.

FAQ

Q1: Can PAC be used for drinking water?
A: Sure. The drinking-water-grade version hits GB15892-2020 rules. With the right amount, leftover aluminum stays low, under WHO and EPA safe marks.

Q2: How should PAC be stored?
A: Seal it up, keep it dry, and hide it from the sun. Liquid PAC might split a touch after sitting long. A fast stir fixes it right up.

Q3: What’s the ideal pH range for PAC?
A: It shines between pH 5 and 9. Go outside that, and the breakdown slows. Coagulation just doesn't pack the same punch.