US Patent 7998240 Process of preventing as elution from copper slag

A process of water-granulating copper smelting slag can readily suppress elution of As from the copper smelting slag. A process of water-granulating a copper smelting slag with granulation water in a circulating system, includes granulating the copper smelting slag with the granulation water; settling suspended solids from the granulation water circulating in the system in a settling tank followed by discharging part of the granulation water through the settling tank from the system; and feeding supplementary water having a concentration of As of 0.01 mg/L or less into the system in such an amount that the total amount of the granulation water circulating in the system is kept constant; wherein the amount of granulation water discharged through the settling tank is such that As eluted from the copper smelting slag after water granulation is 0.01 mg/L or less.