Method for recovering germanium

A method for recovering germanium from exhaust gas exhausted during manufacturing of a preform for an optical fiber,

• the exhaust gas including acidic exhaust gas, and
• the method comprising:
• a first step of bringing the exhaust gas into contact with circulating water of a cooling tower to move germanium in the exhaust gas into the circulating water;
• a second step of supplying the circulating water and a soluble iron salt to a reception tank after the first step;
• a third step of neutralizing the circulating water after the second step;
• and
• a fourth step of settling a precipitate in the circulating water after the third step,
• wherein the first step to the fourth step are set as one cycle and are repeatedly executed in two or more cycles,
• in the second step of a second or subsequent cycle, at least a part of the precipitate obtained as the soluble iron salt in the fourth step is injected into the reception tank, and
• the precipitate is taken out after executing the first step to the fourth step in a predetermined number of cycles.