石灰石对低品位铜矿生物堆浸过程中黄铁矿的抑制作用

Inhibitory effect of limestone on pyrite during bio-heap leaching of low-grade copper ore

福建某企业采用“生物堆浸-萃取-电积”的方式处理低品位硫化铜矿,生产阴极铜。该堆浸工艺为永久堆作业方式,存在酸、铁过剩问题,通用的做法是通过末端中和的方式,将二级萃取后的低铜萃余液中和至pH值7~8,但该方法因电积液中夹带铁离子浓度较高而降低了电流效率,而且还存在中和成本高和中和渣堆存的问题。本文为了从源头解决生物堆浸酸、铁过剩问题,提出在堆浸矿石中混入石灰石矿粒、增加耗酸脉石含量的思路,并采用不同批次矿石进行了试验,考察了石灰石配比及喷淋强度对矿石中铜、铁浸出率以及酸耗的影响,得出以下结论:随着石灰石配矿比例升高,吨矿酸耗以及浸渣中黄铁矿含量均依次递增,表明石灰石配矿可以抑制黄铁矿浸出,减少体系对外产酸产铁;增大喷淋强度,有助于避免pH值剧烈变化,因而可以减少铜、铁离子的水解沉淀,促进铜、铁的浸出;石灰石配矿可将浸出体系电位在较长时间内维持在较低区间(450~550 mV vs.Ag/AgCl),而较低的电位有助于抑制黄铁矿氧化,减少对外产酸产铁。

A low-grade copper sulfide ore was treated by bio-heap leaching-extraction-electrowinning method to produce cathode copper in a Fujian enterprise.The heap leaching process applies a permanent heap operation mode,generating a problem of excess acid and iron.The common practice is to neutralize the low copper raffinate after secondary extraction to a pH 7-8,however,this method reduces the current efficiency due to the high carry-over iron ions in the electrowinning solution,and also generates problems of high neutralization cost and neutralization residue storage.In order to solve the problem of excess acid and iron in bio-heap leaching at source,this paper puts forward the idea of mixing limestone particles into heap leaching ores to increase the content of acid-consuming gangue,and carries out test work with different batches of ores.The effects of limestone content ratio and spray intensity on the extractions of copper and iron,and other parameters were investigated,and the following conclusions were drawn.With the increase of the proportion of limestone ore blending,the acid consumption and the pyrite content in the leaching residue increase,indicating that the limestone can inhibit the leaching of pyrite and reduce the system's external acid production and iron production;increasing the spray intensity is helpful to avoid the drastic change of pH value,thus reducing the hydrolysis precipitation of copper and iron ions and promoting the leaching of copper and iron;limestone blending can maintain the low potential(450~550 mV vs.Ag/AgCl)of the leaching system for a long time,and the lower potential helps to inhibit the oxidation of pyrite and reduce the production of external acid and iron.