A question for context:
What is this website used for? It sounds like ecommerce of some sort.
Filters are often placed at the top of the screen, often as a drilldown to a refined search. You'll find a common ecommerce pattern on desktop of left hand filter areas, but look at what amazon does on mobile. They have a sliding right panel, then give an indication of a filter count (2 in this screenshot).
Filters provide users additional constraints on a general search term. Using a top to bottom model, take a look at this screen, as it goes from the general to the specific:
The one drawback in this design (just my opinion) is that the filters could be a little more prominent, and perhaps sticky. But that's just an opinion, and I doubt amazon has released this without extensive testing.
Having the filter button at the bottom of the screen can be confusing for several reasons:
Your sites controls are competing (on safari web) with a bottom navigation bar and other controls. Have a filter button stack on top of this would add more visual noise. The filter button seems like it would need to be sticky as well, otherwise there needs to be a scroll down to get to it.
If users do need to scroll to some fixed page bottom, you'll need to apply finite results so I don't have to endlessly scroll. Then you have another problem: How do I even know what's below? My assumption is just a list of products. It's not discoverable.
Filter is an aspect of search (and categories). Since you list the category, or the search results at top, my expectation is to augment the category or search close to where it's located.
See another example from Yelp. There's some toggles to scope your results close to the search, and there's a prominent Filter button right there.