using modified concrete for removing chromium from wastewater

background: annual large amounts of wastewater can be entered into the environment from domestic, agricultural, and industrial sources that contain high concentrations of chemical materials and heavy metals. chromium (cr) is one of the most important environmental pollutants, which can cause pollution of water resources and disorder in the metabolic activities of living organisms.[objectives]in this study, we used the alteration in the concrete structure by iron oxide nanoparticles and rice husk ash (rha) to remove cr as a heavy metal from sewage.[methods]rice husk ash was used in the structure of concrete as a forty percent by cement weight. samples were made according to sewage condition and concrete required strength of purification pools. samples surface was covered with nanoparticle, rha, rha and nanoparticle. different sewage concentrations of cr were made from the range of 1 to 1000 ppm. the effects of parameters, such as contact time, adsorbent dose, ph, concentration of cr in sewage, and cr absorption were examined.[results]the maximum absorption was obtained 99.7%, in the contact time of 6 hours, dose of adsorbent 20 mg/l, ph 3, and cr concentration in sewage 10 ppm at the laboratory temperature. cr absorption followed the freundlich model of adsorption.[conclusions]the combination of nanoparticles and rha showed well efficiency for cr absorption from sewage.