As(III) removal from aqueous solutions using simultaneous oxidation and adsorption process by hierarchically magnetic flower-like Fe3O4@C-dot@MnO2 nanocomposite

Abstract

In the present study, a magnetic flower-like Fe₃O₄@C-dot@MnO₂ nanocomposite was synthesized by hydrothermal method and applied for As(III) removal by oxidation and adsorption process. Individual property of the entire material (i.e. magnetic property of Fe₃O₄, mesoporous surface property of C-dot and oxidation property of MnO₂) make the composite efficient with good adsorption capacity for As(III) adsorption. The Fe₃O₄@C-dot@MnO₂ nanocomposite had a saturation magnetization of 26.37 emu/g and it magnetically separated within 40 s. The Fe₃O₄@C-dot@MnO₂ nanocomposite was able to reduce the 0.5 mg/L concentration of As(III) to 0.001 mg/L in just 150 min at pH 3. Pseudo-second-order kinetic and Langmuir isotherm model agreed with experimental data. The uptake capacity of Fe₃O₄@C-dot@MnO₂ nanocomposite was 42.68 mg/g. The anions like chloride, sulphate and nitrate did not show any effect on removal but carbonate and phosphate influenced the As(III) removal rate. Regeneration was studied with NaOH and NaClO solution and the adsorbent was used for repeated five cycles above 80% removal capacity. The XPS studies proposed that As(III) first oxidized to As(V) then adsorb on the composite surface. This study shows the potential applicability of Fe₃O₄@C-dot@MnO₂ nanocomposite to high extent and gives a suitable path for the proficient removal of As(III) from wastewater.