Adsorption removal of methyl violet dye by α-fe2o3 and aminated α-fe2o3 metal oxide composites synthesized via solvothermal process

Abstract

The discharge of persistent artificial dyes, like the cationic methyl violet (MV) dye from textile industrial sewages, requires the development of efficient, cost-effective, and recyclable adsorbents. This work reports on the synthesis of hematite (α-Fe2O3) and amino-modified α-Fe2O3 via the solvothermal method. The effects of surface amination on the nanomaterials' physicochemical attributes were probed by the adsorption of MV wastewater. Successful amine functionalization was confirmed using FTIR and elemental analyses. SEM analysis revealed porous spherical morphologies with an enhanced surface texture following amination. XRD and TGA confirmed the structural stability and thermal resilience of the nanomaterials. Zeta potential showed that the aminated α-Fe2O3 carried a negative surface charge above pH 3, favoring the cationic dye adsorption. The aminated material exhibited a maximum MV adsorption capacity of 10.21 mg/g with equilibrium data conforming to the Langmuir isotherm (R2 = 0.978) as compared to the Freundlich (R2 = 0.662) and Temkin (R2 = 0.634) isotherms, while kinetics data fitted the pseudo-second-order model (R2 = 0.966). The regeneration of aminated α-Fe2O3 sorbent with 0.4 M HCl favoured reclaim for four successive cycles with a slight decrease in efficiency of about 19%. The study demonstrates that the solvothermally produced α-Fe2O3 is a promising low-cost adsorbent for the removal of organic dyes in wastewater treatment applications.