Sciencemadness Discussion Board

Ferric Ammonium Citrate Disposal

Spock - 12-1-2019 at 18:17

I have 150 ml of ferric ammonium citrate solution that I need to dispose of. It's grown mold and I need to head back to school for the semester. I'd prefer to avoid dumping it straight down a drain as it's toxic to fish. I'm thinking to add sufficient sodium hydroxide to precipitate all the iron out as Fe(OH)3, which being rust, shouldn't be any issue to dispose of. Does this seem like a reasonable disposal method?

phlogiston - 13-1-2019 at 09:10

You don't mention the concentration.

I don't think you need to be overly worried about its toxicity to aquatic life. All of the ions in solution are common in the environment already, except citrate, but that too will be easily and quickly broken down by microorganisms in the environment. Iron salts are used on a large scale to fertilise plants. Our local gardening store sells multi-kilogram bags of iron salts for the garden.

If you really want, you could do as you propose, but you should expect some ammonia gas to evolve as well, especially if you add an excess of hydroxide. Do it outside when there is some wind.
Furthermore, the iron hydroxide precipitate will form a gel, not a clean powder. If you were planning to remove it by filtration, it will take very long.



[Edited on 13-1-2019 by phlogiston]

unionised - 13-1-2019 at 13:18

The purpose of the citrate in the compound is to keep the iron in solution as a complex.

One way to dispose of it would be to put it into a soft drink.
https://en.wikipedia.org/wiki/Irn-Bru

The mold might be a bigger hazard than the ferric ammonium citrate.

CharlieA - 13-1-2019 at 17:12

Isn't rust ferric oxide, not ferric hydroxide?

j_sum1 - 13-1-2019 at 18:16

Rust is a pretty generic term for mixed iron oxides and hydroxides and complexes.

DavidJR - 13-1-2019 at 18:39

Just pour it down the drain. Honestly, it's pretty innocuous stuff.

woelen - 14-1-2019 at 02:06

Indeed, just down the drain with it, or flush it away in the toilet.
Iron(III) is not an issue at all, it is a very common ion in nature.
Citrate also is common, in tropical regions it is present in all kinds of fruits.

MrHomeScientist - 14-1-2019 at 06:44

I usually take "rust" to mean red iron oxide, Fe2O3. But actual rust is probably a complex mixture of oxides, hydroxides, and carbonates.

The way I think about disposal is get your chemicals into the least soluble form possible, then dispose in regular trash. This goes to an incinerator, which will calcine everything into even less soluble forms. So your iron hydroxide, for example, would burn into iron oxide anyway.

There are exceptions, of course. Don't throw away arsenic or mercury :D

DavidJR - 14-1-2019 at 07:25

Quote: Originally posted by MrHomeScientist  
I usually take "rust" to mean red iron oxide, Fe2O3. But actual rust is probably a complex mixture of oxides, hydroxides, and carbonates.

The way I think about disposal is get your chemicals into the least soluble form possible, then dispose in regular trash. This goes to an incinerator, which will calcine everything into even less soluble forms. So your iron hydroxide, for example, would burn into iron oxide anyway.

There are exceptions, of course. Don't throw away arsenic or mercury :D


Since when is 'regular trash' incinerated?

fusso - 14-1-2019 at 07:55

I had threw some solution containing Fe3+ and oxalate down the drain too, no worries.

MrHomeScientist - 14-1-2019 at 10:56

Quote: Originally posted by DavidJR  
Quote: Originally posted by MrHomeScientist  
I usually take "rust" to mean red iron oxide, Fe2O3. But actual rust is probably a complex mixture of oxides, hydroxides, and carbonates.

The way I think about disposal is get your chemicals into the least soluble form possible, then dispose in regular trash. This goes to an incinerator, which will calcine everything into even less soluble forms. So your iron hydroxide, for example, would burn into iron oxide anyway.

There are exceptions, of course. Don't throw away arsenic or mercury :D


Since when is 'regular trash' incinerated?

It is here. It's how our area handles "recycling," through a Waste-To-Energy (WTE) facility. An excerpt from one of their emails:
Quote:
A WTE facility, unlike an incinerator which just burns waste, extracts energy from the waste. A WTE facility is basically an electrical power plant that utilizes waste as a fuel source, versus coal or natural gas. With over 500 facilities, WTE facilities are fairly common in Europe. In the United States, which only has 71 WTE facilities, they are still somewhat of a rarity. In the County, almost all of the combustible household and commercial waste is processed at the WTE facility and is converted into electrical energy.

In addition to the electrical power generated from the combustion process, all of the metals, both ferrous and non-ferrous, are extracted from the ash residue and recycled.

As a general rule, unless the WTE facility is inoperable or is operating above rated capacity, the County landfill is only used as a repository for the ash residue left over from the combustion process or for the disposal of non-burnable materials that cannot be processed at the WTE. This dramatically increases the life of the landfill. The County landfill was opened in 1987 and was expected to reach capacity in 2019. Because of the operation of the WTE facility, the last landfill life estimate extends the date that the landfill is expected to reach capacity out to 2047.

Pretty cool stuff, really. I assumed that other areas had incinerators at least, if not WTE facilities. You should of course consider your own area's local waste handling procedures to inform your own personal ones.

[Edited on 1-15-2019 by MrHomeScientist]

fusso - 14-1-2019 at 16:14

Oops sorry, deleted.

j_sum1 - 14-1-2019 at 16:17

Quote: Originally posted by fusso  
Oops sorry, deleted.


Thanks for looking after that, fusso. Gracious of you.