Short tips: when a drive has been formatted for Linux (like a SDCard for a RPI) and you want to clean it ans reuse it as a normal (Fat32) drive, you can’t do it from Diskutil graphical tool.
Here are the way to make it with the command line. Assuming your drive is /dev/diskX and the drive is unmounted.
# get the list of partitions [~] sudo diskutil list ... /dev/diskX (external, physical): #: TYPE NAME SIZE IDENTIFIER 0: FDisk_partition_scheme *4.0 GB diskX 1: Windows_FAT_32 boot 58.7 MB diskXs1 2: Linux 3.9 GB diskXs2
Here we have 2 partitions to remove
[~] sudo diskutil eraseVolume free none diskXs1 [~] sudo diskutil eraseVolume free none diskXs2
Now we can create a new one:
[~] sudo newfs_msdos -F 32 /dev/diskX
The created partition will get the full disk size.