Add-PSSnapin Microsoft.SharePoint.PowerShell

# Connect to sharepoint and site
$web = Get-SPWeb "*full link to site"
$list = $web.Lists["*name of library*"]
$time = Get-Date -Format g

# Get all folders in library which aren't approved
Write-Host -f white "Retrieving all folders not set to Approved Status in"$list.Title"library..."
$folders = $list.RootFolder.subFolders | where {$_.Item.ModerationInformation.Status -ne "Approved"} | select *

# Loop through the folders
foreach($folder in $folders) {
    Write-Host -f white "Attempting to update"$folder.Name

    # Update the status to approved and set a comment
    $folder.Item.ModerationInformation.Status = "Approved"
    $folder.Item.ModerationInformation.Comment = "Bulk Approved folder - " + $time

    # Try to update the folder in SP and notify user
    try {
        $folder.Item.Update()
        Write-Host -f green $folder.Name"in"$list.Title"library updated succesfully"
    } catch {
        Write-Host -f yellow "Failed to update"$folder.Name"folder in"$list.Title"library"
    }
}