Adsorption of malachite green dye on different natural absorbents modified with magnetite nanoparticles

This study was focused on the adsorption of malachite green as a cationic dye on magnetite nanoparticles loaded green tea waste (MNLGTW), peanut husk (MNLPH), Azolla (MNLA) and Fig leave (MNLFL) as naturally cheap sources of adsorbent. MNLGTW, MNLPH, MNLA and MNLFL were prepared with chemical precipitation method and they were characterized with Fourier transform infrared spectroscopy (FT-IR), powder X-ray diffraction (XRD), Scanning electron microscopy (SEM) and Energy Dispersive  X- ray (EDX) analysis. Different parameters affecting the dye removal efficiency were optimized. At optimum conditions, the sorption of the malachite green on theMNLGTW, MNLPH, MNLA, and MNLFL adsorbents was best described by a pseudo second-order kinetic model with R2 =1, qeq= 12.51 mg g-1 , R2 =0.9996, qeq=625 mg g-1 , R2 =0.9842, qeq=0.5772 mg g-1 and R2 =0.9912, qeq=0.517 mg g-1   respectively. Equilibrium data were fitted wellto the Langmuir isotherm more than Freundlich and Temkin isotherm. The synthesized sorbent showed complete dye removal with 112.359, 98.039, 23.1 and 73.2 mg g-1 for MNLGTW, MNLPH, MNLA,and MNLFL, respectively. The results showed MNLGTW, MNLPH, MNLA and MNLFL can be used as efficient adsorbents for removal of malachite green from aqueous solutions.