All funds received as rent in connection with the leasing of public lands under §§ 4510 and 4511 of this title shall be payable to the State Treasurer and kept by him or her in a special account known as the “Department of Natural Resources and Environmental Control Public Lands Account,” and such funds shall not become a part of the General Fund of the State except as hereinafter provided. The Department may expend money payable out of the special account for the protection, improvement or restoration of lands demised or of lands adjacent to any public lands demised. Any balance remaining from the rentals of any public land in the special account and unencumbered at the end of any fiscal year reverts to the General Fund. Such funds shall not be encumbered for any purpose whatsoever except for the purposes hereinabove provided.