Can I use knitting wool for crochet

Yes, you can use knitting yarn and wool for crochet. There are so many different types of yarn and knitting wool and all of them can be used one way or other. More challenging is to match the yarn with the project and choose the right size crochet hook to go with the yarn. The only yarns which I personally would consider more carefully will be mohair / kid silk type, what I call "fluffy" yarns, as they can present challenge in tight tension projects. However, if you are crocheting loose and airy shawl, the mohair type yarns will work  beautifully.