Removal of Chromium from Industrial Wastewater

Chromium is not presented in natural water. However it enters to water resources from industrial wastewater such as electroplating, tanning, pigment, dye, printing, etc. which causes serious problems in the environment. Here studies carried out on the wastewater of a tanning factory (Mashhad Hemmatabad).UV-Visible studies showed that this kind of wastewater contains chromium (III) only. The samples have been converted to dichromate by treating with ammonium persulphate in presence of silver nitrate and few drops of concentrated sulphuric acid. The measurements have been done by atomic absorption spectrophotometry with nitrous acetylene flame.By ploting the absorption verses concentration (2-9ppm) a straight line is obtained wich has a relative standard deviation of 1.63%. When standard deviation is thrice the detection limit comes out to be 0.1mg/lMany of reference discussed the removal of metallic ions from industrial wastewater by ionic exchange processes, thus we tried to remove chromium by the process of semicontinu in column using humic acid as a natural cationic exchanger.The results showed that, under optimum conditions, from a wastewater containing 162.56 mg/lit of Cr (III) ion it is possible to remove 96.27%. In this experiment thers is no need of any chang in the pH.