You can use this method.
$fileUrl = url for file on sharepoint
$destinationfolder = destinationFolder
function ProcessURL {
param($fileUrl,$destinationfolder)
$file = $web.GetFile($fileUrl)
$destinationfolder = $destination + "/" + $folder.Url
if (!(Test-Path -path $destinationfolder))
{
$dest = New-Item $destinationfolder -type directory
}
#Download file
$binary = $file.OpenBinary()
$stream = New-Object System.IO.FileStream($destinationfolder + "/" + $file.Name), Create
$writer = New-Object System.IO.BinaryWriter($stream)
$writer.write($binary)
$writer.Close()
#Delete file by deleting parent SPListItem
$list.Items.DeleteItemById($file.Item.Id)
}