Catalyst synthesis and application in oxidation assays

Hydrocarbons contaminated soil remediation is a critical issue since soil is a complex media, mainly because of its heterogeneity. Thereby literature lacks studies involving in situ chemical oxidation focusing on soil remediation. Clays can be an important proposal as support to heterogeneous catalyst for oxidation process, due to their natural abundance and eco-friendly characteristic. Different clay-based catalysts were synthesized through 23 experimental design varying sodium hydroxide (NaOH), ferrous sulfate (FeSO4) and ferric sulfate (Fe3(SO4)2) concentrations. A set of different synthesized catalysts were applied in phenanthrene (PHE) contaminated soil oxidation to evaluate the activation of the sodium persulfate (SP) and hydrogen peroxide (HP) oxidants. Values of PHE removal from contaminated soil were used as response. At the experimental conditions studied, most of the produced catalysts proved to be efficient in activating both oxidants, achieving around 80% of PHE removal from soil. Control assays presented that around 20% of PHE can be naturally transferred to liquid phase and PHE removals from soil did not occur during oxidation without clay modification, i.e., using raw clay. The selected catalyst obtained the best oxidant activation with NaOH concentration of 0.625 M, ferrous sulfate concentration of 137.25 gL-1 and ferric sulfate concentration of 274.50 gL-1

烃类污染土壤修复是一项关键课题，土壤作为复杂介质，其非均质性特征使得该问题极具挑战性。现有文献中针对土壤修复的原位化学氧化（in situ chemical oxidation）相关研究仍较为匮乏。黏土因天然储量丰富且环境友好，可作为氧化过程中非均相催化剂（heterogeneous catalyst）的载体，具备重要应用潜力。本研究采用2³析因实验设计，通过调控氢氧化钠（NaOH）、硫酸亚铁（FeSO₄）与硫酸铁（Fe₃(SO₄)₂）的投料浓度，合成了一系列黏土基催化剂。将所合成的系列催化剂应用于菲（phenanthrene, PHE）污染土壤的氧化修复体系，以评估其对过硫酸钠（sodium persulfate, SP）与过氧化氢（hydrogen peroxide, HP）两种氧化剂的活化效果，实验以污染土壤中菲的去除率作为响应指标。在所考察的实验条件下，绝大多数制备得到的催化剂均可高效活化两种氧化剂，对土壤中菲的去除率可达约80%。空白对照实验结果显示：约20%的菲可自然转移至液相中；而未经过改性的原生黏土作为载体时，氧化过程无法实现土壤中菲的有效去除。最优催化剂的制备参数为：氢氧化钠浓度0.625 M、硫酸亚铁浓度137.25 g·L⁻¹、硫酸铁浓度274.50 g·L⁻¹，该催化剂可实现最佳的氧化剂活化效果。