Science Buddies: "Ask an Expert"

am trying to remove the microplastics using various coagulants in order to increase the size of the microplastics by making the floc. I will use these coagulants:

Al2(SO4)3 . 18H2O
AlCl3
FeCl3
Fe2(SO4)3
FeSO4

So the experiment will be simple: mix microplastics+each coagulants+water and compare the result.
I am going to use five different types of plastics to make microplastics (thinking of 3mm so I can actually see them). For the water, I might use seawater. It depends on what's more alike with dosed water in wastewater treatment plant... I need to do more research.

However, I have no idea how to use coagulants.
1) Do I have to use the actual solid coagulants? Or should I use solution(if so, what %??)?
2) How much coagulants should I put??
3) I also want to find out the temperature of water that each coagulants best work. Is the jar test only way?

Additionally, what would you recommend more? Just pure water or seawater? I want to make sure that my experiment is similar with wastewater treatment system..

Hi,
This is a cool project idea! However, like many novel projects, its going to require some optimization before the actual experiment can begin.

Regarding temperature and composition of the water, I think you should contact a waste treatment plant and ask about treatment temperature, and a feasible water substitute. I think what you really want is 'gray' fresh water, defined as "the relatively clean waste water from baths, sinks, washing machines, and other kitchen appliances." Maybe someone else will have an idea of how to mimic that.

Importantly: unless your treatment plant incorporates sea water into its system, I think you should stay away from anything with high salt content. Your coagulants are salts, and could react with ions already in the sea water, forming solid particles that precipitate out of solution. This won't help you find a good plastic coagulant.

You have some good variables - different plastics, different coagulants. But the question of coagulant concentration needs to be incorporated into your experiment. This is going to be an important aspect, because if a coagulant works only at a very high concentration, its not likely to be that feasible on a real-world scale.

Regarding using solid or already dissolved coagulants, you'll just have to try them both and see what works better. Just be sure you know the final concentrations in each of your test conditions.



I hope this helps get your started! Let us know when you have more questions.

I am working on the coagulation of the Microplastics. I want to use Aluminum Chloride, Aluminium Sulphate, Ferric Chloride, Ferric Sulfate, and Ferrous Sulfate as my coagulants. However, I can only find the Heptahydrate form of Ferric Sulfate,Ferrous Sulfate, and Aluminium Sulphate. Is it okay to just use them? If not, where can I get those chemical with cheap price? (Max budget is $80 for 3 chemicals). Can I email bio(?) professors to get the chemicals? Thank you.



Moderator note: I've merged this post with your previous post on the same topic. Please keep your posts together so the expert who has been helping you can see that you have a follow-up question. Thanks!