He wanted to blow up the suits. Tony later has surgery to have the shrapnel removed from his chest with an arc reactor powered electromagnet catching the broken pieces once theyre removed. Later Tony doesn’t need the arc reactor and tosses it into the sea.

He does not need the one in his chest to stop the shrapnel, apparently they were able to remove it at the end of Iron Man 3, but his suits still need to be powered so there is new arc reactor which only powers suits.
Each suit has its own reactor. This was demonstrated in Iron Man 2 and 3 as the suits in the armory all had arc reactors.

He used the arc reactor to remove the bomb pieces which were struck in his heart later removing those particles he doesn’t needed it so he threw it but the arm ours used by tony are powered by arc reactor so he thought there is a lot of things to do with this arc reactor and he made one

He want to remove the some bomb pieces he remove arc reactor

Maybe because he wanted to get rid of the particles in his body