The green synthesis of palladium oxide nanoparticles using Dictyota indica seaweed extract was investigated. Dictyotales is a large order in the brown algae (class Phaeophyceae). The color of the reaction mixture changed which indicated the formation of palladium oxide nanoparticles. UV-Visible, SEM, TEM, XRD, and FTIR analysis determined the characteristics of synthesized nanoparticles. The UVVisible analysis showed the formation of palladium oxide nanoparticles. SEM and TEM analyses presented the palladium oxide nanoparticles have a spherical shape and based on DLS analysis with the average particle diameter of 19nm. The comparisons of the nanoparticle size with different biological synthesis were studied which revealed this methodology offers the smallest size. The crystallographic parameters of the synthesized Pd nanoparticles were as follows: crystalline structure (cubic), space group (Fm-3m), and lattice parameter (a=5.6500, b=5.6500, c=5.6500, α=90, β=90, and γ=90). FTIR analysis indicated the presence of a palladium oxide group in the product. The removal efficiency of cadmium by the palladium oxide nanoparticles was investigated to optimize the pH, contact time, dose of adsorbent and concentration of cadmium. The results showed that optimum conditions for cadmium removal from water were obtained at pH 8, 500 mg/l adsorbent dose and 20 min contact time, wherein in these circumstances the removal of cadmium was 82.82%. The adsorption isotherms primacy was as follows, Langmuir R2=0.9904> Freundlich R2=0.9857> Temkin R2=0.8791.

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