Abstract
In this study, iron nanoparticles (FeNPs) were synthesized via a green method using loquat (Eriobotrya japonica) leaves aqueous extract as a renewable reducing agent. The synthesized FeNPs were characterized by DLS, XRD, FT-IR, SEM/EDX, and TEM analysis, and then, they were used as an adsorbent for Cr(VI) removal from aqueous solutions. Batch adsorption experiments were carried out to investigate the optimum adsorption parameters such as the initial pH of the solution, temperature, initial Cr(VI) concentration, and adsorbent concentration. The optimum adsorption conditions were determined as initial pH 3.0, temperature 45°C, and adsorbent concentration 1 g/L. Also, a linear increase was observed in adsorbed Cr(VI) amounts with the increasing initial Cr(VI) concentrations. The biosynthesized FeNPs showed the high removal levels higher than 90% for Cr(VI) adsorption at a wide range of initial Cr(VI) concentrations (50–500 mg/L). The experimental equilibrium data were modelled with Langmuir and Freundlich isotherm models, and it was found that experimental equilibrium data could be well described by the Langmuir isotherm model. The maximum monolayer coverage capacity of FeNPs for Cr(VI) adsorption was found to be 312.5 mg/g. The pseudo-first-order and the pseudo-second-order kinetic models were applied to the experimental adsorption data, and it was concluded that the data were defined as the best agreement with the pseudo-second-order kinetic model. Weber–Morris model was used to investigate the effect of mass transfer on the adsorption of Cr(VI) onto FeNPs; it was observed that both the film (boundary layer) and intraparticle diffusion affected the studied adsorption process. The thermodynamic studies suggested that Cr(VI) adsorption onto FeNPs was endothermic and nonspontaneous, and the positive ΔS value indicated increased disorder at the solid-solution interface during the adsorption.
Highlights
IntroductionWater pollution is one of the most important burning environmental issues among the various kinds of environmental pollution since water resources are contaminated by a variety of organic, inorganic, and biological pollutants due to day-to-day utilization and potential applications of water at domestic, industrial, and agricultural areas all over the world [1, 2]
Water pollution is one of the most important burning environmental issues among the various kinds of environmental pollution since water resources are contaminated by a variety of organic, inorganic, and biological pollutants due to day-to-day utilization and potential applications of water at domestic, industrial, and agricultural areas all over the world [1, 2].e heavy metals are the best known nonbiodegradable water pollutants which are extremely toxic and dangerous for the ecosystem, agriculture, and human health [3].e chromium ions exist in industrial wastewaters both trivalent and hexavalent forms
0.995 0.995 0.991 0.998 0.992 0.996 and prepared FeNPs were tested as an adsorbent for Cr(VI) removal under our experimental conditions. e conclusions of this study can be summarized: (i) e characterization studies confirmed the synthesis of FeNPs successfully. e synthesized FeNPs had irregular spherical morphology, and they were relatively agglomerated. e X-ray powder diffraction (XRD) spectrum showed the diffraction peaks belong to mainly iron hydroxide and iron oxyhydroxide
Summary
Water pollution is one of the most important burning environmental issues among the various kinds of environmental pollution since water resources are contaminated by a variety of organic, inorganic, and biological pollutants due to day-to-day utilization and potential applications of water at domestic, industrial, and agricultural areas all over the world [1, 2]. E chromium ions exist in industrial wastewaters both trivalent and hexavalent forms. Cr(VI) ion exists in different forms in solutions as Cr2O72−, HCrO4−, or CrO42− depending on the pH and the Cr(VI) concentration. E Cr(III) species in aqueous solutions is present in the forms of Cr3+, Cr(OH)2+, Cr(OH)2+, Cr(OH), or Cr(OH)4− depending on the solution pH [4, 5]. It is quite harmful to the living organisms because it has the potential to pass through cell membranes and reduces to reactive intermediates. It is quite harmful to the living organisms because it has the potential to pass through cell membranes and reduces to reactive intermediates. ese reactive
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