Removal of Hexavalent Chromium from Aqueous Solutions Using Magnetic Nanoparticles Coated With Alumina Modified by Cetyl Trimethyl Ammonium Bromide

The development of an effective method for removal of chromium from the environment is of great importance. The aim of this research is to synthesize magnetic nanoparticles coated with alumina modified by Cetyl Trimethyl Ammonium Bromide in the removal of hexavalent chromium through magnetic solid phase extraction method. First, the modified nanoparticles were synthesized and structurally characterized. The factors affecting the process of chromium removal including the concentration of Cetyl Trimethyl Ammonium Bromide, the solution’s pH, the amount of nano particle, the sample’s volume, a proper eloquent, the adsorption and desorption time, and the effect of interfering ions were investigated. Furthermore, the adsorption isotherm, adsorption capacity, and recoverability of the adsorbent were further examined. The modified magnetic nanoparticles are homogeneous, spherical, have a size lower than 20 nanometer with a magnetic property. The optimal conditions for removal of chromium included 7*10-6 mol/L as the optimal concentration of Cetyl Trimethyl Ammonium Bromide, pH range of 6-8, 0.1 g of the nanoparticles, 10 mL the volume of the chromium sample, nitric acid 2 M as a suitable eluent, 15 minutes of adsorption and desorption, and no interference of interfering ions in the process of chromium separation. The process efficiency under optimal conditions was determined to be over 95%. The process followed the Langmuir adsorption isotherm. The adsorption capacity proved to be 23.8 mg/g. Reuse after four times of recovering of the adsorbent was effective in removal of chromium as much as 80%. The accuracy of the method for five measurement times was 4.155% and the method’s detection threshold was 0.081 mg/L. The method enjoys the benefits of convenient preparation of the adsorbent, high selectivity, high accuracy, short process time, and high-efficiency in removal of chromium from aquatic environments, lending itself to be used in real samples.