How to restore color of brick floor?

I have a brick floor area leading to my rear door and it has a chalky appearance and not much of the color shows. Prevoius owner kept a cat littler box in the area, and abused it, I tried to scrub with soap solution and push broom with little effect. How should I go about cleaning it? Any particular chemicals? I even thought about wire brush...and then maybe sealing it somehow. Any ideas would be helpful.