I don't think there is anyway to save your futon mattress. If it's soaked with urine, no amount of cleaning is going to get it out. If you go buy a new one, chances are the cat will use that as a litter box too. You should probably take the cat to the vet. It could be a UTI or some other medical issue. I had to get rid of a cat that I had for over 10 years after our daughter was born. He was peeing in the corners and nothing I did would make him stop., I tried literally everything. Take her to the vet, but you may have to get rid of her :(
mattress cleaning urine cat - Pain In The Glass
Cushions and mattresses can be cleaned in a fashion similar to carpets. Soak the affected area of the cushion with water. Blot up as much of the cat urine as possible with a towel, then soak the cushion by very slowly pouring the enzyme cleaner on and around the affected area. Let it sit for 15 minutes, then squish out as much of the excess enzyme cleaner as possible before blotting with towels. If possible, leave the cushion outside as long as possible while it dries. Since cushions take days to dry, lay aluminum foil down before putting the cushion back, then put a second layer of foil over the top of the cushion to discourage your cat from peeing on the cushion again.
Feb 28, 2017 - Clean Cat Urine Mattress
However, a few days after cleaning, the smell of cat urine returned. The smell kept coming back after every cleaning so we decided to switch mattresses with an older one we had on a guest bed. It has been several months now and there is still a smell of cat urine that lingers on the mattress. We have kept the cats out of the guest bedroom so there have not been any additional accidents. We would like to get the smell out and buying a new mattress is not an option.
How can I get old cat urine smell out of a mattress