Rate of Leaching from Rare Metal Ore

在搅拌槽中进行了焙烧锌矿和氧化镍矿的硫酸浸出试验。锌矿石的浸出分为两个阶段：第一阶段是氧化锌的浸出，第二阶段是锌铁氧体的浸出。第一阶段速度非常快，因为锌、铜和镉在100秒时的浸出率分别达到94%、60%和77%。浸出速率依次为镉、铜、锌，受温度和矿石粒度的影响较大。在第二阶段，镉、铜、铁和锌的浸出率几乎相同，浸出率很低，需要大约12小时才能完全浸出。在氧化镍矿石的浸出中，镍、钴、镁和铁的浸出率相似，但铬的浸出率很低。在60min时，镍和镁的浸出程度为90%，钴和铁的浸出程度为80%，铬的浸出程度为17%。浸出速率受温度和酸浓度的影响较大，但受矿石颗粒大小的影响不大。未反应核模型适用于焙烧锌矿第一阶段“浸出A”阶段的锌浸出，而不适用于铜和镉的浸出。事实表明，铜和镉与锌不同，它们在矿石中的分布并不均匀。对于锌矿石和氧化镍矿浸出的第二阶段“浸出B”的解释，可采用体积反应模型：浸出活化能在17.4~23.1kcal/mol之间，表明浸出的一个速率控制步骤是化学反应。

Experiment has been conducted for the leaching from roasted zinc ore and nickel oxide ore by sulfuric acid in a stirred tank. Kinetics for the leaching has been discussed on the basis of observed results.The leaching from zinc ore is characterized by two stages: the first stage "leaching A" resulting from the leaching of zinc oxide; the second, "leaching B"from the leaching of zinc-ferrite. The first stage is very rapid, since the extent of leaching of zince, copper, and cadmium at 100 sec attains to 94, 60, and 77 %, respectively. The rate of leaching is higher in the order, cadmium, copper, and zinc, being affected more by temperature and the size of ore particle. In the second stage, cadmium, copper, iron, and zinc are leached at almost the same rate which is so low that complete leaching requires about 12 hr.In the leaching from nicked oxide ore, nickel, cobalt, magnesium, and iron are leached at similar rate, though chromium at very low rate. The extent of leaching at 60 min, almost at a terminal stage, is 90 % for nickel and magnesium, 80 % for cobalt and iron, and 17 % for chromium. The leaching rate is influenced much by temperature and acid concentration, but not so much by the size of ore particle.The unreacted-core model can be applied to the leaching of zinc in the first stage "leaching A" for the roasted zinc ore, but not to those of copper and cadmium. The fact suggests that copper and cadmium, unlike zinc, are nonuniformly distributed in the ore. As for the explanation of the second stage "leaching B" for the zinc ore and the leaching from nickel oxide ore, the volume reaction model can be adopted: Activation energy for the leaching ranges from 17.4 to 23.1 kcal/mol, which implies that a rate-determing step in the leaching is chemical reaction.