物表面作用时,它的极性部分—OCSS-固着在矿物表面,而将非极性基R朝外定向排列。由于非极性基的疏水作用,从而提高了矿粒表面的疏水性。当这种附着有黄药阴离子的矿粒与气泡接触时,矿粒表面的黄药非极性基插入气泡,并随着气泡上浮到矿浆表面(下图)。这就是黄药捕收硫化矿基本原理。
对于黄药如何附着于硫化矿物表面,有两种假说,即“化学假说”和“半氧化假说”。化学假说认为,黄药附着于矿物表面是由于黄药与矿物表面发生普通的化学反应所致。同一金属的黄原酸盐溶度积因黄原酸盐非极性基烃链长度和结构变化而不同,烃链长,溶度积不,而溶度积越小的黄原酸盐则浮选效果越好。
从下表可以看出,金属硫化和的溶度积远较相对应的黄原酸盐的溶度积为小,因此,要生成黄原酸盐的沉淀是不可能的。化学假说解释这个问题是极为困难的。
normal style="MARGIN: 0cm 0cm 0pt; TEXT-ALIGN: center" align=center>金属硫化物、黄原酸盐、二硫代磷酸盐的溶度积(
normal style="MARGIN: 0cm 0cm 0pt; LINE-HEIGHT: 11pt; TEXT-ALIGN: center; mso-line-height-rule: exactly" align=center>金属阳离子 | normal style="MARGIN: 0cm 0cm 0pt; LINE-HEIGHT: 11pt; TEXT-ALIGN: center; mso-line-height-rule: exactly" align=center>乙基黄药 | normal style="MARGIN: 0cm 0cm 0pt; LINE-HEIGHT: 11pt; TEXT-ALIGN: center; mso-line-height-rule: exactly" align=center>二 硫 代 磷 酸 盐(黑药) | normal style="MARGIN: 0cm 0cm 0pt; LINE-HEIGHT: 11pt; TEXT-ALIGN: center; mso-line-height-rule: exactly" align=center>硫 化 物 | ||
normal style="MARGIN: 0cm 0cm 0pt; LINE-HEIGHT: 11pt; TEXT-ALIGN: center; mso-line-height-rule: exactly" align=center>二乙基 | normal style="MARGIN: 0cm 0cm 0pt; LINE-HEIGHT: 11pt; TEXT-ALIGN: center; mso-line-height-rule: exactly" align=center>二丁基 | normal style="MARGIN: 0cm 0cm 0pt; LINE-HEIGHT: 11pt; TEXT-ALIGN: center; mso-line-height-rule: exactly" align=center>二甲酚基 | |||
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半氧化假说认为,黄药不是与表面完全氧化的产物起反应,而是与表面经过轻微氧化生成与晶格紧密结合的硫化物——硫酸盐结合体起反应:
这样形成的不溶性黄原酸铅与晶格中的PbS相结合,形成稳固的薄膜罩盖在矿粒表面,使矿粒疏水易浮。而铅钒或过度氧化的方铅矿表面之所以难溶,是由于完全氧化物(如PbSO4)易溶于水,它于黄药反应生成的黄原酸铅薄膜不可能与矿粒牢固结合,因此不易浮游。实验表明,表面纯净的方铅矿,在无氧气存在时,不能用黄药浮选,但只要有少量的氧气存在便能进行浮选。由此说明,半氧化假说释黄药捕集机理是比较正确的。