I believe the association of fire with purification in both Old and New Testaments is easily traceable. I won't list proof texts, but they do abound, and probably others will take the time to present those in detail. In the Old Testament the prophetic analogy of silver being purified by fire is classically representative of the purification theme of the Bible.

I would say that, typically true of him, Paul, gets to the heart of the matter when he writes about every man's work being tried by fire, yet the man, himself, being saved. John, whose theology parallels Paul's more explicit style, with a more implicit style of his own, makes it a point to call the lake in question not only the lake of fire, but also of brimstone, which is an old word for sulfur. With sulfur being a common agent of ceremonial purification in temples of worship in ancient times, I think the association is obvious in the Book of Revelation.

Now, to specifically address the possibility that John means to convey destruction rather than purification, let me say that neither scripture nor science recognizes the destruction of anything in the sense of annihilation, that is, of anything being reduced to a state of absolute nothingness. Destruction does not render anything nonexistent, but rather incapable of carrying out its function, as in the destruction of a tank in warfare. The mass of metal is still there, but it can't function as a tank any longer.

Even if you were to vaporize the tank completely, yet, it's intrinsic elements would still exist in other forms. Contrary to conventional theology, all things were not created from nothing.  And none of the things that have been created will ever face nonexistence -- by that I mean nonexistence in any form. All created things are subject to change, change in form, but not subject to losing their intrinsic existence.

So, what we have in the process of purification by fire is, first, a separation of the object of purification from all that defiles it, all that is foreign to it's intrinsic constitution, and then the removal of the corrupting element(s). But, as all analogies and parables fall short, in some way, of fully representing the truth they are meant to convey, so is the case here.

In the case of death and Hades being cast into the lake of fire and a separating of these foreign elements of corruption from the persons who are subjected to the divine flame, it is clear that the persons are saved. They are delivered from the corruption to which they were subjected, but other scripture indicates that death, that last (ultimate) enemy is not merely discarded, but is swallowed up in victory.  I think the Holy Spirit very specifically inspired Paul to write of swallowing up and not mere discarding and certainly not annihilation.

When something is swallowed it undergoes a quite remarkable process whereby it becomes, physically speaking, part and parcel of the swallower himself. It is transformed into blood, bone and tissue and has become integral to the person's body. The Book of Hebrews uses the analogy of shaking. Everything that can be shaken will be removed by that shaking, but what then?

This brings us to the depth and extent of reconciliation in the economy of God. Certainly, God has reconciled the alienated person to Himself in Christ, that is undeniable in the scripture, but beyond that, God does not defeat death and the place/Hades [the capacity and potential] of death, by merely removing them. He takes alienation, enmity and hostility themselves and reconstitutes them back into the grace out of which they first proceeded. In a word, God defeats his enemies by transforming them into friends.

At the heart of the message of the Book of Revelation is majestic statement of Him who sits upon the throne, "Behold, I make ALL THINGS new." God loses nothing. The loss of anything does not compute when it comes to God. He created good and evil, the prophet said, and in the end, all things return to God that "He might be all in all."