STUDY ON LEACHING CHARACTERISTICS OF HEAVY METALS IN TITANIUM GYPSUM

The content and leaching characteristics with different leaching conditions of heavy metals in titanium gypsum were studied． The results indicated that the content of main trace elements of titanium gypsum such as Mn，Hg，Zn，Cr，As，were relatively high，showing the potential risk to the surrounding environment． The leaching under different extracting agents showed that the highest leaching concentration of heavy metals occurred in the seawater with the exception of Zn，and then H2 SO4 /HNO3 and deionized water，even the seawater concentration of Hg exceded standard limit． In the test of continuous static leaching，the leaching concentration of heavy metals continued to decrease both in saline and acid mixture，whereas the leaching amount in seawater was always higher，meaning that the promotion of salinity on heavy metals leaching could continue with time and a strong acid buffer capacity of titanium gypsum was observed． Simultaneously，with the continuous leaching process，the cumulative leaching rate of heavy metals increased significantly both in two agents，indicating a strong heavy metal release capability still in the liquid-solid leaching system of titanium gypsum in addition to the standard accelerated leaching time，and the pollution control measures should be taken for the titanium gypsum of simple stockpiling because of its potential environmental risk．