From 37d38261e41cea79d67d33f3cd833181bafd41a3 Mon Sep 17 00:00:00 2001 From: Mark van Renswoude Date: Thu, 8 Nov 2018 21:17:04 +0100 Subject: [PATCH] Updated disposal (markdown) --- electronics/disposal.md | 54 ++++++++++++++++++++++++++++++++++++++++- 1 file changed, 53 insertions(+), 1 deletion(-) diff --git a/electronics/disposal.md b/electronics/disposal.md index 949f119..0cbd332 100644 --- a/electronics/disposal.md +++ b/electronics/disposal.md @@ -6,8 +6,60 @@ ___ [[_TOC_]] +## Disclaimer +I am no where near qualified enough to claim these notes are accurate. When in doubt, take the waste material to your local disposal. + ### Sodium metasilicate +Safe to mix with water and pour down the drain as far as I can find. + +### Sodium hydroxide +Can be neutralised with an acid, which we should have: ### Ferric chloride +Besides deactivating the acid, there's also the issue of the copper dissolved in the spent ferric chloride which is detrimental to the environment. -### Sodium hydroxide \ No newline at end of file +These instructions were found on [[https://wiki.london.hackspace.org.uk/w/index.php?title=Project:Deactivating_a_ferric_chloride_solution&redirect=no]]. I've copied them here in case the site goes down: + +> **Example** +> +> A solution that was made with a packet of ferric chloride (FeCl3) crystals weighing 300 grams requires 222 grams of sodium hydroxide (NaOH) to be deactivated. +> +> After deactivation, the neutralised solution will contain iron hydroxide (Fe(OH)3) which is rust and sodium chloride (NaCl) which is common table salt. +> +> Both are innocuous and can be poured down the drain. +> +> **Method** +> +> Pour the spent ferric chloride solution in a plastic bucket - do not use metal buckets, add about 5 times its volume of water. Dissolve 222 grams of sodium hydroxide in about 3 litres of water. +> +> In a thin stream, add the sodium hydroxide solution to the ferric chloride and stir. Once it turns rust coloured it is ready to be discarded. +> +> If not discarded, on standing, the iron hydroxide will separate out at the bottom, while at the top, a crust of copper carbonate (CuCO3) will form due to the copper from etched circuits. +> +> The iron hydroxide at the bottom is a standard commercial pigment and can be separated off the solution and added to latex paint. +> +> **In Theory** +> +> Ferric chloride reacts with sodium hydroxide turning into ferric hydroxide and sodium chloride. +> +> FeCl3 + 3 NaOH → Fe(OH)3 + 3 NaCl +> +> The proportions are: +> +> 1 mole of FeCl3 which is 91,3g reacting with 3 moles of NaOH which is 120g. +> +> The mass of 1 mole is obtained by adding together the atomic masses obtained from the periodic table of elements: +> +> Iron (Fe) has the atomic mass of 55.8 (grams/mole) and Chlorine (Cl) has the atomic mass of 35,5 (grams/mole). +> +> Ferric chloride (FeCl3) will then have the molecular mass of 55.8 * 1 + 35.5 * 3 = 162.3 g/mole. +> +> To find how many moles are contained in 300 grams of ferric chloride the calculation is 300/162.3 = 1.85 moles of ferric chloride. +> +> Conversely; Sodium (Na) ~ 23 g/mole, Oxygen (0) ~ 16 g/mole and Hydrogen (H) 1 g/mole totalling 40 grams per mole. +> +> Each mole of FeCl3 requires 3 moles of NaOH (sodium hydroxide) at 40 grams per mole. +> +> The weight of Na0H required to deactivate the spent FeCl3 solution is obtained thus: +> +> 1.85 * 3 = 5.55 moles of NaOH, at 40 g/mole that will be 5.55 * 40 = 222 grams NaOH. \ No newline at end of file