按列内容匹配的字符串

I have a huge data frame and several key words (all non numeric). I want to write R code to go over the whole data frame and look for the columns where the sentences contain one or more of these key words. Then if there was a match to put the key words in the same row in a new column (if more than one matching put them both separated by a comma or in a new column as well).I have a huge data frame and several key words