Dechlorination of Selected Pesticides in Water using Catalytic Bimetallic (Fe–Pd) Nanoparticles Immobilized on MgAlO Support

Chlorinated pollutants commonly found in contaminated water include pesticides such as fipronil, chlorpyrifos, dieldrin, diuron and 1,1,1-trichloro-2,2-di(4-chlorophenyl)ethane (DDT), chlorinated phenols and polychlorinated biphenyls (PCBs), as well as industrial solvents, especially trichloroethylene (TCE) among others. Most of these pollutants are toxic, carcinogenic, and are said to be endocrine disruptors. Biodegradation is a confirmed benign technology for the control of these pesticides,Pesticides despite being problematic due to the presence of the strong carbon–chlorine bond that is always involved. In this research, we aimed to develop an effective, safe, and cheap dechlorinationDechlorination process using bimetallic nanoparticle iron–palladium (Fe–Pd) catalyst. The use of an inert porous metal oxide catalyst support is an ideal strategy as it is capable of preventing agglomeration, providing a large surface area for binding with the nanoparticles. This prevents metal leaching and thus, improves separation by filtration. We report the dechlorination of chlorpyrifos and dieldrin using Fe–Pd nanoparticles immobilized on magnesium aluminum oxide (MgAlO) support. The metal oxide supportMetal oxide support was synthesized by the coprecipitation of Mg(NO ₃) ₂·6H ₂ O and Al(NO ₃)₃·9H₂O with NaOH and Na₂CO₃to yield Mg₆Al₂CO₃(OH)₁₆·4H₂ O. The calcined MgAlO gave average surface area, particle size, pore volume, and pore diameter of 223.69 m ² g ⁻¹, 21.4 nm, 0.89 cm ³g⁻, and 15.9 nm. Particle size investigation with scanning electron microscope (SEM) and nanosizer of the Fe–Pd-loaded MgAlO showed a staggering increase to 1406 nm. X-ray diffraction (XRD) results confirmed that only the periclase crystalline structure was present in the MgAlO. SEM/EDS (electron-dispersive spectroscopy) was also used to confirm the molar ratios which are reported in percentage compositions. Pesticide model solutions analysis using two-dimensional gas chromatograph bearing a time-of-flight mass spectrometric detector (GC × GC-TOFMS) shows that dechlorinationDechlorination of trace level (5 ppm) of chlorpyrifos achieved 92.6 % removal after 1 h while that same concentration of dieldrin was 96 % after 3 h. Dieldrin dechlorination was found to follow first-order kinetics while that of chlorpyrifos followed pseudo-first order with an activation energy (E_a) of 34.34 kJ. Conclusively, mineralization for chlorpyrifos and dieldrin attained 36 and 45 % degradation,Degradation respectively.