Systems and methods for recycling waste plastic can convert the waste plastic into a form of purified crude oil that includes one or more organic molecular species and that is free, or substantially free, of impurities such as acids and metals. In some systems and methods, the plastic is heated under vacuum conditions to effect depolymerization of the plastic, which yields a vapor, and the vapor is then directly contacted with a pH adjusted solution in a vapor treatment system. In some systems and methods, a continuous batch process is employed.