Disposal of hydrochloric acid
You can neutralise the acid by mixing with alkali.  However, be careful.

You will need quite a lot of something like baking powder.  Or if you have any left over - cement powder.

Add a small amount to the acid - it will foam and release gas (Carbon Dioxide).  Don't add too much at once or the bucket will overflow and you will get acid everywhere.

Keep going, small amount at a time until it no longer foams when you add more.  You now have salty water that can be poured down the drain.

I repeat, be careful because of the foaming and you will need a lot of powder.