Selectivity of Malachite Green on Cationic Dye Mixtures Toward Adsorption on Magnetite Humic Acid

Magnetite humic acid (MHA) was successfully synthesized by the coprecipitation method followed by hydrothermal process, as evidenced by the XRD, FTIR, VSM, and SEM analysis characterization results. XRD diffraction shows diffraction peaks at 2θ=21.53º, 35.95º, and 57.93º. The FTIR spectra have a typical absorption at 3,410, 1,589, 1,396, 1,026, 910, 794, and 540 cm-1. Magnetite humic acid was paramagnetic with magnetization (Ms) 17.04 emu/g. Humic acid and magnetite humic acid have an irregular structure; the morphology of magnetite humic acid is smoother than humic acid. Malachite green was more selective than methylene blue and rhodamine B on magnetite humic acid. The adsorption of malachite green on humic acid and magnetite humic acid was carried out at pHpzc 8.06 and 6.08. The adsorption capacity (Qmax) of humic acid (77.519 mg/g) and magnetite humic acid (169.492 mg/g) were found with pseudo-second-order kinetic and Langmuir isotherm models. After five regeneration cycles, the adsorption percentages of malachite green with humic acid and magnetite humic acid ranged from 94.67-61.37% and 62.03-21.11%, respectively. Magnetite humic acid has high stability and reusability. The good regeneration of MHA was supported by the XRD diffractogram. Magnetic properties in the material simplify the adsorption process and minimize the potential for damage to the surface of the material.