Role of Soil pH for Enhancing DDT Remediation by Using Synthesised Iron Oxide Nanoparticles

Abstract

This study investigates the influence of soil pH on the catalytic degradation of dichlorodiphenyltrichloroethane (DDT) using iron oxide (Fe2O3) nanoparticles, monitored by the characteristic absorption peak of DDT at 270 nm within the 220–300 nm spectral range. To determine the ideal conditions for nanoparticle-mediated reductive dechlorination, the degradation efficiency was assessed in acidic, neutral, and alkaline pH ranges. The results showed that DDT degradation achieved its maximum (58.7%) at pH 5, which was explained by increased corrosion of Fe2O3 nanoparticles and increased production of reactive Fe(II) species in acidic environments. Degradation efficiency reduced to 22.5% at neutral pH 7, most likely as a result of oxide/hydroxide layers stabilising the surface and decreasing electron transport. Due to the creation of passivating layers and reduced Fe(II) release, alkaline (pH- 9) condition inhibited reductive reactions and caused minimal degradation (0.44%). In order to optimise iron nanoparticle catalytic activity for successful DDT remediation in contaminated soils, our results emphasise the crucial role that pH plays in regulating nanoparticle surface chemistry and reactivity, highlighting the necessity of pH optimisation or buffering in field applications. Overall, the results show that the effectiveness of DDT remediation is highly dependent on the pH of the surrounding environment and indicate that maintaining the soil slightly acidic could enhance the catalytic efficacy of iron oxide nanoparticles in field applications.

Introduction

Organochlorine pesticides (OCPs), such as DDT, are among the most persistent and hazardous organic pollutants due to their chemical stability and resistance to natural degradation. India is a major producer and consumer of pesticides, with organochlorines accounting for about 40% of pesticide use, leading to significant environmental contamination. Conventional treatment methods are often ineffective in removing these pollutants and may generate even more toxic by-products, creating a need for advanced remediation techniques.

Nano-remediation has emerged as a promising solution, utilizing nanomaterials with unique physicochemical properties to remove organic pollutants efficiently. Iron oxide nanoparticles, in particular, are attractive due to their low toxicity, biocompatibility, biodegradability, and high reactivity. These nanoparticles can catalyze the degradation of pollutants through processes such as photocatalysis and reductive dechlorination, with effectiveness strongly influenced by environmental pH.

In this study, the degradation of DDT in soil was investigated using synthesized iron oxide nanoparticles under different pH conditions. Batch experiments were conducted at acidic (pH 5), neutral (pH 7), and alkaline (pH 9) conditions, and DDT degradation was monitored using UV–Vis spectrophotometry. Results showed that DDT degradation was highest at acidic pH, reaching approximately 58.7% at pH 5, due to enhanced corrosion of iron nanoparticles and increased formation of reactive Fe(II) species. Degradation decreased to about 22.5% at neutral pH and was minimal (around 0.44%) under alkaline conditions, where nanoparticle passivation reduced reactivity.

References

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Copyright

Copyright © 2025 Madhuri Singh, Dr. Parveen Parihar. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.