Extraction system

An extraction system that causes an extraction liquid to extract metal ions from a raw material liquid that is an aqueous solution containing the metal ions, the extraction system comprising:

• a raw material liquid tank holding the raw material liquid;
• an extraction liquid tank holding the extraction liquid;
• an extractor that is connected to the raw material liquid tank to allow the raw material liquid to be led from the raw material liquid tank into the extractor and that is connected to the extraction liquid tank to allow the extraction liquid to be led from the extraction liquid tank into the extractor, the extractor carrying out an extraction treatment of bringing the raw material liquid led in from the raw material liquid tank into contact with the extraction liquid led in from the extraction liquid tank so that the metal ions are extracted from the raw material liquid to migrate to the extraction liquid;
• a separator connected to the extractor so as to receive, from the extractor, a mixture liquid of the raw material liquid and the extraction liquid that have been subjected to the extraction treatment, the separator separating the received mixture liquid into the raw material liquid and the extraction liquid;
• a raw material liquid return path that connects the separator to the raw material liquid tank so as to lead the separated raw material liquid from the separator to the raw material liquid tank, the separated raw material liquid being the raw material liquid separated by the separator;
• an extraction liquid return path that connects the separator to the extraction liquid tank so as to lead the separated extraction liquid from the separator to the extraction liquid tank, the separated extraction liquid being the extraction liquid separated by the separator;
• and
• a raw material liquid pH regulator addition apparatus connected to a raw material liquid pH adjustment place that is one of the raw material liquid tank and the raw material liquid return path, the raw material liquid pH regulator addition apparatus configured to add a raw material liquid pH regulator to the raw material liquid in the raw material liquid pH adjustment place, the raw material liquid pH regulator being a pH regulator that increases pH of the raw material liquid, the pH having been decreased by the extraction treatment.