Remediation of Chlorpyrifos‐Contaminated Soils by Laboratory‐Synthesized Zero‐Valent Nano Iron Particles: Effect of pH and Aluminium Salts

Abstract

Degradation of the insecticide chlorpyrifos in contaminated soils was investigated using laboratory synthesized zero-valent nano iron (ZVNI) particles. The synthesized ZVNI particles were characterized as nanoscale sized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The zero-valent state (Fe0) of iron was confirmed by EDAX analysis and the morphology of the ZVNI particles was studied by XRD. Batch experiments were conducted by treating the chlorpyrifos contaminated soil with ZVNI, our results indicate that 90% of chlorpyrifos was degraded after 10 days of incubation. Only 32% degradation was observed with micro zero-valent iron (mZVI) and no considerable degradation was attained without ZVNI. The degradation of chlorpyrifos followed the first-order kinetics with a rate constant and a half-life of 0.245 day−1and 2.82 days, respectively. Degradation was monitored at two different pH values, that is, pH 10 and pH 4. Chlorpyrifos degradation rate constant increased as the pH decreases from 10 to 4. The corresponding rate constant and half-lives were 0.43 day−1and 1.57days for pH 4, 0.18 day−1and 3.65 days for pH 10. In addition, an attempt was made by augmenting Al2(SO4)3with ZVNI and it was found that the degradation rate of chlorpyrifos was greatly enhanced and the rate constant was rapidly increased from 0.245 day−1to 0.60 day−1. Hydrolysis and stepwise dechlorination pathway of chlorpyrifos with ZVNI was the dominant reaction.

Enhance degradation of insecticide chlorpyrifos by iron salts and potassium persulfate during zerovalent iron treatment in aqueous solution

“…Devlin and Allin [11] observed that the reactivity of granular iron during the reduction of 4-chloronitrobenzene was increased by a sulfate, either owing to an increase in the ZVI surface activity or in its sorption capacity. Similar trend of experimental finding was reported by Reddy et al [27], who stated that the degradation rate of chlorpyrifos was greatly enhanced by augmenting Al 2 (SO 4 ) 3 with ZVI. During the ferric nitrate-amended Fe 0 treatment of chlorpyrifos, 44.6, 46.2, and 47.6% of the chlorpyrifos was removed within 24 h after treatment with 0.1, 0.5, and 1.0% (w/v) ferric nitrate, respectively (Fig.…”

Biodegradation of chlorpyrifos by bacterial genus Pseudomonas

“…Another pathway was reported by Ref. for the breakdown of 2,3‐dihydroxypyridine to yield maleamic acid, further oxidises to form carbondioxide, water, ammonium carbonate, and sodium chloride.…”

Remediating Chlorpyrifos-Contaminated Soil Using Immobilized Microorganism Technology

“…This showed that the immobilized carrier can protect the degrading bacteria and shield the harmful effects of the outside to a certain extent. Li Ying [30] showed that after degrading bacteria were immobilized, its tolerance to acid and alkali was significantly raised, but too acid or too alkaline also had an adverse effect on the biodegradation of chlorpyrifos (p<0.05). Compared with free bacteria, the sensitivity of immobilized bacteria to pH was decreased.…”