灰岩溶解对锑静态吸附与界面固定的影响

Effects of Limestone Dissolution on Static Adsorption and Interfacial Fixation of Antimony

摘要: 研究选取广西阳朔典型铅锌矿流域土壤和灰岩，采用静态批实验，结合XRD和FTIR表征，探究了Sb (III)和Sb (V)在土壤–灰岩混合介质中的吸附行为与固定机制。结果表明：灰岩掺入对Sb (III)和Sb (V)的固定能力存在明显的比例效应，90%土壤 + 10%灰岩混合介质对两种价态锑的吸附容量最高，其固定优势并非随灰岩比例增加而持续增强。适量灰岩(10%)的掺入能通过增强碳酸盐缓冲、提供Ca²⁺并扩展反应界面以促进固定；而过量掺入(30%)则会稀释土壤中铁锰氧化物等高活性组分，且高浓度$HC{O}_3^{-}$ 与$Sb{\left(OH\right)}_6^{-}$ 发生竞争吸附，导致固定能力下降。环境因子(pH、Ca²⁺和富里酸)显著调控Sb的界面分配，且Sb (V)与Sb (III)的响应行为因形态差异而不同。XRD和FTIR表征表明，吸附后主体矿物相稳定，未生成新生含Sb晶相，固定机制以表面作用为主导，主要涉及方解石及低结晶Fe/Mn活性组分表面络合、配体交换及界面低结晶沉积。本研究为认识岩溶区土壤中不同价态Sb的吸附差异及其固定机制提供了实验依据。

Abstract: This study selected soils and limestone from a typical lead-zinc mining watershed in Yangshuo, Guangxi, and employed static batch experiments combined with X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR) to investigate the adsorption behavior and fixation mechanisms of Sb (III) and Sb (V) in a soil-limestone mixed medium. The results showed a clear proportion-dependent effect of limestone amendment on Sb (III) and Sb (V) immobilization, with the 90% soil + 10% limestone mixture exhibiting the highest adsorption capacity for both valence states; this advantage did not increase continuously with limestone proportion. An appropriate addition (10%) promoted immobilization by enhancing carbonate buffering, supplying Ca²⁺, and expanding the reactive interfacial area. In contrast, excessive addition (30%) diluted highly reactive soil components such as Fe/Mn oxides and induced competitive adsorption between elevated $HC{O}_3^{-}$ and $Sb{\left(OH\right)}_6^{-}$ , thereby reducing immobilization capacity. Environmental factors (pH, Ca²⁺, fulvic acid) significantly regulated Sb interfacial partitioning, with Sb (V) and Sb (III) responding differently due to speciation differences. XRD and FTIR analyses indicated that major mineral phases remained stable post-adsorption without newly formed Sb-bearing crystalline phases, suggesting that Sb immobilization was dominated by surface processes—primarily surface complexation, ligand exchange, and interfacial poorly crystalline precipitation on calcite and low-crystallinity Fe/Mn reactive components. This study provides an experimental basis for understanding differential adsorption and fixation mechanisms of antimony valence states in karst soils.