There are different methods of purification for different things:

One method of purification is washing.  The substances, which can be used for washing are the following:

Pure water, everything which is pure and flows, Rose water, vinegar, the water of coconut and watermelon.

On the contrary, impurity (Najaasat) cannot be removed with milk, oil, etc. because oiliness is found in these.

Things which have any impurity on them can be purified through washing and those things which are themselves impure e.g. urine, stools cannot be purified.  (But if their inherent nature is changed, then they may become pure)

The second method of purification is changing of its state or if it is changed by mixing anything like drug/medicine in it.  By this every impure thing becomes pure and clean regardless of whether their impurity is inherent or temporary.

The third method of purification is wiping with wet hands or wet cloth or any wet thing.  Those substances which do not absorb water can be purified with this method e.g. mirror, sword, knife, iron and any such thing.  If they have any impurity on then, by wiping with a wet cloth the impurity can be removed.

The fourth method is burning it completely.  Stone, soil and those things which cannot absorb water can be purified by burning also.  In this way their impurity is removed.

The fifth method is to remove the impurity by rubbing, scratching, scraping or any such method.  This method is only for purifying the body and cloth on which the semen is there.  The condition is that the semen should be dried and should come off.  If the semen is not dried up then the cloth or the body part cannot be purified until it is washed.

The sixth method is peel off and rub using knife or nails or any such thing or rubbing on the ground.   Things which are made from leather/hide, etc. are purified with this method like shoes, socks, gloves, etc.

The seventh method is to dig or turn over, i.e. digging the land and turning it over completely in a way that the impurity and/or effects should not be felt in the bottom layer.

The eighth method is to dry.  Those things which grow on land can be purified by drying them in sunlight, fire or air provide it should still be attached to the land e.g., trees, grass, wooden pillars, door, threshold of the door.

The ninth method is to draw water from a well or tank, etc.  If any impurity, human being, animal or bird falls in a well and dies than first the impurity or dead body should be removed.  Then after drawing the required quantity of water from the well or tank, its water, its walls and even the soil/mud in it is purified.

And Allah (Subhanahu Wa Ta’ala) knows best.