Is a semi-colon used to separate a dependent clause from an independent clause?

Not usually. It's more common to use a comma. For example, in the sentence:

"If I have time, I'll go to the store." the "If I have time" phrase is the dependent clause as it cannot stand on its own and be a complete sentence. The independent clause is "I'll go to the store" as it's a complete sentence in its own right. Typically the two sentences are joined by a comma, although the Word "then" can also be used (e.g., If I have time then I'll go to the store).