Read the documentation again : setTexture takes a Texture*, that is, a pointer to a texture.
So you'd need to do :
rect.setTexture(&rectTexture);
But that's not the only problem here.
First, you shouldn't load the texture
every time you're drawing the tile. Rather, you should keep the texture alive somewhere else (it's easier if you use OOP with classes and all, you could put the texture as a class member).
If you want to draw a tile map, there's a better solution : VertexArray.
First, you'll need to have only
one image file containing all your possible tiles. Then, you'll tell the VertexArray which part of that texture you want to use for each tile.
The VertexArray is not trivial to use, so you'll need to read the doc carefully.
Now, some people have done it before you, and you may want to make use of that :
Thor is a helper library for SFML that makes many tasks easier, including tilemaps.