Leaching Mechanism And Conditions Of Extractants On Mobile Forms Of Elements In Soils

Reasearch is focused on developemt of exploration techniques for covered terranes to find new mineral deposits. Although great efforts had been paid by scientists to develop new geochemical exploration techniques for deeply buried deposit, it’s still the one of major challenge. In the past two decads, international mineral exploration enterprises and commercial chemical laboratories have reinforced their research activities on the leaching techniques and taken strict patent protection on their kernel methods.The leaching mechanisms of extractants on metal mobile forms are discribed. The specified extractants for copper, uranium and gold concealed deposits are developed respectively. Experiments on various analytical conditions are conducted to find out its effects on the leaching results. The new leaching methods had been successfully applied in three-type concealed deposits.(1) Occurrences of mobile forms of elements in soils are classified into three categories:(a) Mobile Precursor Form; (b) Loosely Bounded Form; and (c) Terminated Chemical combination Form. The development of leaching method for Mobile Precursor Phase should be emphasized for further development.(2) Mechanisms of selective leaching techniques for mobile form of elements are discussed. The nonlinear kinetic model is established to simulate the leaching course for mobile precursor phase elements. The leaching kinetic model initiatively realizes the mathematic analogy and quantitative analysis of the leaching course.(3) Based on the metal ion diffusion and ligand theory, specific extractants (MML-Cu MML-U and MML-Au) suitable for base, gold and uranium mobile forms respectively. The comparison experiments for the new extractants with the novel digests were conducted to justify its specialization for the target elements.(4) A leaching procedure for mobile forms of elements is established. The large volume circulating shaker with auto temperature control system and solid-solution separation equipment are developed. The experimental conditions, such as temperature, acidity, sample and solution ratio etc., are improved for the standardization of the leaching procedures.(5) A pilot regional geochemical survey for sandstone-type uranium deposits at a sampling density of 1 sample per 4km2 was firstly conducted across a area of 2000 km2 at Dongshang area, Ordos basin. The separation of -200 mesh soil grains can be effecitive to delineate geochemical anomalies both in outcropping and concealed areas. Application of the extractant of MML-U to selective leaching of mobile uraium from soils along four traverses over the uranium deposit indicates U, Mo, V anomalies over the deposit. The MML-Cu leaching method has been conducted at Zhouan concealed copper-nickel deposit at a depth of 400-700 metres. Anomalies of Cu, Ni, Cr, Fe and Mg were delineated around the concealed ultramafic intrusion containing Cu-Ni ore bodies...