Synthesis and Characterization of Pd-Ni Bimetallic Nanoparticles as Efficient Adsorbent for the Removal of Acid Orange 8 Present in Wastewater

Ali Umar,Muhammad Khan,Sultan Alam,Steven Dc Rubin,Anna Kallistova,Muhammad Zahoor,Juris Burlakovs,Nikolai Pimenov,Ivar Zekker,Gourav Bhowmick

doi:10.3390/w13081095

Abstract

In this study palladium-nickel (Pd-Ni) nanoparticles supported on carbon and cerium oxide (Pd-Ni/AC-CeO2) were synthesized by a transfer phase method and characterized by scanning electronic microscopy (SEM), X-ray diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDX). The XRD and SEM data concluded the presence of alloy formation between Pd and Ni. The synthesized particles were used as an adsorbent for removal of azo dye acid orange-8 (AO-8) from water and were found to be effective in removal (over 90% removal efficiency) of the selected dye. Different kinetics and equilibrium models were applied to calculate the adsorption parameters. The most suitable model that best fitted the equilibrium data was the Langmuir model and maximum adsorption capacities were 666.6, 714 and 769 mg/g at 293, 313 and 333 K, respectively, with R2 values closed to 1 while in the case of the kinetics data the best fit was obtained with a pseudo-second order kinetics model with a high R2 value. Furthermore, the adsorption thermodynamics parameters such as free energy, enthalpy, and entropy were calculated and the adsorption process was to found be exothermic with a value of ΔH° (−7.593 kJ mol−1), spontaneous as ΔG° values were negative (−18.7327, −19.4870, and −20.584 kJ/mol at 293, 313 and 333 K, respectively). A positive entropy change ΔS° with a value of 0.0384 kJ /mol K indicates increased disorder at the solid–solution interface during the adsorption process. An attempt was made to recycle the Pd-Ni/AC-CeO2 with suitable solvents and the recycled adsorbent was reused for 6 cycles with AO-8 removal efficiency up to 80%. Based on findings of the study, the synthesized adsorbent could effectively be used for the removal of other pollutants from wastewater, however, further studies are needed to prove the mechanisms.

Highlights

Various industries i.e., plastic, leather, textiles, etc. use different synthetic dyes to color surfaces of material objects and protect them from corrosive and environmental damage
The morphological studies of Pd-Ni nanoparticles supported on activated carbon and cerium oxide were carried out using scanning electronic microscopy (SEM) analysis
Palladium-nickel (Pd-Ni) nanoparticles supported on activated carbon and cerium oxide were prepared and characterized through various instrumental techniques

Summary

Introduction

Various industries i.e., plastic, leather, textiles, etc. use different synthetic dyes (azo dyes) to color surfaces of material objects and protect them from corrosive and environmental damage. Degradation and decolorization of textile dyes by different microbial strains have been shown in a recent study [1]. Of AO-7, AO-8 and other azo dyes have been shown to be represented in water and there are possibilities of treatment with aerobic decolorization techniques. Organization has estimated the share of dyes from textiles industry in water pollution that is about 17% to 20% of all the industrial water pollution sources. In the textile industry about 80% of the dyes used are azo dyes out of which nearly 10% to 15% are discharged into wastewater treatment plant effluent and enter water bodies thereby causing water pollution. Discharge of azo dyes alter pH and chemical composition of water and cause environmental imbalance, and an increase in chemical oxygen demand (COD) and biological oxygen demand (BOD) of water. The azo dyes are non-biodegradable and, overall, they are carcinogenic in nature due to the presence of the −N=N− (azo-)

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