Cr(VI) removal from water by magnetic ferrihydrite: adsorption performance and adsorbent characterization

Abstract

ABSTRACT The present work reports a noveladsorbent of magnetic ferrihydrite by coprecipitation and neutralisation hydrolysis method for to remove Cr(Ⅵ) from water. The effects of various factors including pH, adsorbent dosage, initial Cr(VI) concentration, adsorption time on the adsorption performance were investigated. Under the conditions of pH = 6, 20 mg/L Cr(Ⅵ) concentration, 0.1 gmagnetic ferrihydrite, and 4 h adsorption time, the Cr(Ⅵ)removal efficiency reached up to 90%. The adsorption isotherms forCr(VI) was well fitted by the Freundlich model. And The adsorption kinetics data for magnetic ferrihydritewere better fitted to a pseudo second-order model, indicating the dominant role of chemisorption. Scanning electron microscopy (SEM), specific surface area (BET), X ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and Vibrating Sample Magnetometer (VSM), X-ray photoelectron spectrometer (XPS) were used to characterise the structure of magnetic ferrihydrite. The prepared magnetic ferrihydrite has a uniform pore size and a specific surface area of 153.520 m2/g. It can be concluded that the magnetic ferrihydrite adsorbent was successfully prepared. Compared with other adsorbents of iron hydroxide, magnetic ferrihydrite has obvious advantages of high adsorption capacityand can be easily separated. Moreover, adsorption regeneration experiments confirmed that the adsorbent can be reused successfully for Cr(VI) removal and has promising potential for practical application.