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

烃污染土壤修复是一项至关重要的课题，土壤作为一类复杂介质，其非均质性是该领域的核心挑战之一。目前学术文献中针对土壤修复的原位化学氧化（in situ chemical oxidation）相关研究相对匮乏。黏土凭借天然储量丰富且环境友好的特性，可作为氧化过程多相催化剂（heterogeneous catalyst）载体的优质候选材料。本研究采用三因素两水平实验设计，调控氢氧化钠（NaOH）、硫酸亚铁（FeSO4）与硫酸铁（Fe3(SO4)2）的投料浓度，合成了多组黏土基催化剂。将上述合成催化剂应用于菲（PHE）污染土壤的氧化修复体系，以评估其对过硫酸钠（SP）与过氧化氢（HP）两种氧化剂的活化性能。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，多数合成催化剂均可有效活化两种氧化剂，对土壤中菲的去除率可达约80%。对照实验结果表明，约20%的菲可自然转移至液相；未经过改性的原生黏土在无催化剂活化的氧化体系中，无法实现土壤中菲的有效去除。本研究筛选得到的最优催化剂，其制备参数为：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