zìcóng wánjù xiāodú yǐhòu, jiù kěyǐ zàilìyòng le.

Chinese very often puts the time, condition, or background first, and then gives the main result.

So the structure is:

• 自从玩具消毒以后 = after/since the toys were disinfected
• 就可以再利用了 = then they can be reused

This is similar to English patterns like:

• After the toys are disinfected, they can be reused.
• Once the toys have been disinfected, they can be reused.

Putting the time/background first makes the logic very clear.

自从 usually means since or ever since. It introduces a starting point in time.

Examples:

• 自从去年开始，我一直很忙。
  Ever since last year, I’ve been very busy.
• 自从搬家以后，他很少来了。
  Since moving house, he rarely comes.

In your sentence, 自从 points to the moment when the toys were disinfected, and the rest of the sentence tells what becomes true from that point.

以后 means after. It turns the action before it into a time expression.

So:

• 消毒以后 = after disinfecting / after being disinfected

In this sentence:

• 玩具消毒以后 = after the toys are disinfected / after disinfecting the toys

A very common pattern in Chinese is:

• verb/action + 以后, then the main clause

For example:

• 吃饭以后，我们去散步。
  After eating, we go for a walk.

They can appear together, and native speakers do say things like this, but it can feel a little stacked because both relate to time.

Broadly:

• 自从 = since, from the point when
• 以后 = after

So 自从……以后 means something like ever since after... or from the time after...

In many cases, learners will more often see:

• 玩具消毒以后，就可以再利用了。
• 自从玩具消毒以后，就可以再利用了。

Both are understandable, but the first is a bit simpler and more straightforward if you just mean after or once.

就 often marks a result that follows naturally, quickly, or directly from what came before.

Here it links the first part and the second part:

• 自从/以后...，就...

So the idea is:

• Once/after the toys are disinfected, then they can be reused.

It gives a sense of then, thereupon, or as a result.

Without 就, the sentence could still be understood, but 就 makes the connection tighter and more natural.

Chinese often omits subjects when they are already clear from context.

Here, 玩具 has already been mentioned, so in the second clause it is understood that we are still talking about the toys.

So:

• 自从玩具消毒以后，就可以再利用了。

means roughly:

• After the toys are disinfected, (they) can be reused.

If you wanted to make it more explicit, you could say:

• 玩具消毒以后，它们就可以再利用了。

But very often Chinese leaves that pronoun out because it is unnecessary.

In context, it means the toys are disinfected or the toys undergo disinfection.

Chinese often leaves the agent unstated if it is not important. So it does not need a passive marker every time.

That means:

• 玩具消毒以后 can be understood as
  after the toys have been disinfected

If you wanted to make the passive idea completely explicit, you could say:

• 玩具被消毒以后

But Chinese frequently avoids 被 when the passive meaning is obvious from context.

Because Chinese does not use the passive marker 被 as often as English uses be + past participle.

English says:

• the toys are disinfected

Chinese can simply say:

• 玩具消毒以后

when the meaning is obvious.

Using 被 is possible:

• 玩具被消毒以后，就可以再利用了。

But it is not required. In many practical or instructional sentences, Chinese prefers the shorter form unless the doer needs to be highlighted.

The final 了 is a sentence-final particle, not the same as the 了 that marks a completed action after a verb.

Here, it signals a new situation or change of state:

• before disinfection: reusing the toys is not okay / not possible yet
• after disinfection: now reusing them becomes possible

So 可以再利用了 means something like:

• can now be reused
• are reusable now

This 了 often appears when something has become true.

Compare:

• 可以再利用。 = can be reused
• 可以再利用了。 = can now be reused / are reusable now

Yes. 可以 is a modal verb, and modal verbs are commonly followed directly by another verb or verb phrase.

So:

• 可以 + 再利用
• 可以 + 去
• 可以 + 看
• 可以 + 说

Examples:

• 你可以进去。
  You may go in.
• 这个可以吃。
  This can be eaten.
• 这些材料可以再利用。
  These materials can be reused.

So 可以再利用 is a perfectly normal structure.

Historically it is 再 + 利用, but in modern Chinese 再利用 is very commonly treated as a set expression meaning reuse or reutilize.

• 再 = again
• 利用 = make use of / utilize

Together:

• 再利用 = use again, reuse

It is more formal than simply saying 再用.

Compare:

• 再用 = use again
• 再利用 = reuse, often in technical, environmental, or formal contexts

So in a sentence about disinfecting toys, 再利用 sounds quite natural if the context is about reusing items safely.

Yes, slightly.

• 再用 is more everyday and conversational: use again
• 再利用 is a bit more formal and often sounds like reuse in a practical or environmental sense

So:

• 玩具消毒以后，就可以再用了。
  After the toys are disinfected, they can be used again.

This sounds more casual and natural in daily speech.

• 玩具消毒以后，就可以再利用了。
  After the toys are disinfected, they can be reused.

This sounds a bit more formal or written.

Yes. Some common alternatives are:

• 玩具消毒以后，就可以再利用了。
• 玩具消毒后，就可以再利用了。
• 消毒以后，玩具就可以再利用了。
• 玩具消毒以后，就可以再用了。

These all keep the same basic meaning, but they vary slightly in style:

• 以后 = neutral, common
• 后 = shorter, a little more concise
• 再用 = more conversational
• 再利用 = more formal

A useful way to see it is:

• 时间/条件 + 以后，(就) + 可以 + 动词 + 了

Applied to this sentence:

• 玩具消毒以后 = after the toys are disinfected
• 就 = then/as a result
• 可以 = can
• 再利用 = reuse
• 了 = now, indicating a new state

So the full pattern means:

• After X happens, then Y becomes possible now.

This is a very common Chinese sentence pattern.