Metal-filtering sponge removes lead from water | Hacker News Reader

Metal-filtering sponge removes lead from water

news.northwestern.edu

94 pointsclouddrover13 comments

I didn't see in the article the volume of water it can filter before the sponge is saturated, and the volume of acidic water it takes to then rinse the sponge of the metals.

Also, after rinsing, how easy is it to recover the rinsed metal from the acidic solution if they want to gather something like cobalt for re-use, which they imply might be something they'd want to do?

Hey! Author from the paper here. The volume of water is dependent on the mass of adsorbent used and the concentration of Pb or other metal in the water. The mg/g values given in a few of the figures/tables for each of the nanomaterial-coated sponges gives the mass of Pb per mass of adsorbent that is the "maximum capacity" for the given adsorbent. So, if there's a 20mg/g capacity, that would imply 1 gram of sponge can remediate 20mg of metal ion in water, which would be, say, 20 Liters of water at 1ppm concentration of the metal ion.

It was slightly outside the scope of our research to discuss utilization of that metal ion, but it is a mostly solved engineering problem. Ideally, the sponge would be regenerated after it was full/at capacity with a metal like Co, with a small volume of water, to generate a high concentration solution of Cobalt, which could then be precipitated out as a metal or Cobalt salt using a strong base, or utilized in applications that require Cobalt in solution, or, with certain metals, incorporated into another mineral straight from solution for use in, say, a battery cathode or other material.

This is why I come to HN. People are already asking the hard questions before I’ve even completed the article. Can anyone answer the OP’s questions? Anyone from the study here?

Lead and other heavy metals, including cobalt. It allows water to be made potable and also effectively mines the water for metals that are in short supply.

Cobalt is toxic to humans. It's also used in the production of lithium-ion batteries and in short supply:

A common ingredient in lithium-ion batteries, cobalt is energetically expensive to mine and accompanied by a laundry list of environmental and human costs.

Probably a dumb question, but could this somehow be integrated into a dialysis process to treat lead poisoning?

Well, if you really want to treat lead poisoning, you need a way to get it out of people's bones and organs. It doesn't stick around in the blood long term. And we already have chelation therapy for getting heavy metals out of blood.

Yeah, I wondered about that. Blood lead levels remain high, though, correct? Seems like an alternative to the significant risks of chelation could be useful?

Given that it is all metals including heavy ones I suspect these sponges would be even worse than chelation, even if it left calcium alone. Hello anemia.

Hey! Author from the paper here! This is not a dumb question at all. There are already pretty good processes for treating lead poisoning, such as chelating agents. These nanomaterials, while not terrible for the body, are probably not the best things to ingest to treat Pb poisoning.

Probably not, lead ions are problematic because of the absorption of lead ions as if they were calcium ions at the cellular level.

This clarified the issue to me. Thanks!

How does the sponge chemically work?

Hey! Author from the paper here! Nanomaterial coatings are applied to the sponges (and could be applied to other membranes, filters, or adsorbents as well) to tailor their surfaces for the adsorption of particular metal ions. These nanomaterials physisorb metal ions with high capacity and specificity due to high surface area and abundant surface sites for adsorption (and desorption for regeneration under acidic conditions).

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