Sorry we didn’t get around to answering your question in the chat.
It’s because it needs a big long answer!
Neutralisation is the act of adjusting the pH of waste water so that it is safe to introduce back into our water supply. This could be waste water from sewage or industrial waste. There’s a couple of different things the can do to neutralise the water. In most cases the problem with the water is that it is acidic, so the use sodium carbonate to neutralise it. here is how sodium carbonate would neutralise hydrochloric acid:
2HCl + Na2CO3 = 2NaCl + H20 + CO2
This neatly solves the problem of acidic water, however, can you see another harmful by-product of this reaction? It’s CO2, carbon dioxide. Excess carbon dioxide entering the atmosphere is a major contributing factor to global warming. It is one of the greenhouse gases. This means that neutralisation has both positive and negative outcomes for the environment.
Lets look at it from a completely different point of view. Sodium carbonate is preferred over other reagents for neutralisation because it’s safe to use and is not toxic or corrosive like some of the alternatives. However, it is quite a heavy solid and vast quantities of it are required to neutralise lots of waste waters. Where does it come from? Sodium carbonate has to be mined and then shipped across the world for useage. And what does transport mean? Yes – more pollution going into the atmosphere! What a catch 22!