Purification of wet phosphoric acid using modified activated carbon

Phosphoric acid is very important to the Tunisian economy. A new method has been developed to reduce the concentration of inorganic impurities present in commercial Tunisian phosphoric acid. This method is based on the modification of activated carbon with sodium dodecyl sulphonate to carry out the exchange of ions. The preliminary results with the column used for this purpose was shown to be effective; the concentration of Cd in the acid was reduced to approximately zero, V was reduced with 86% and Zn, B & Cr were reduced with 50%. Another system (activated carbon–sodium diethyldithiocarbamate) was tested for the purification of phosphoric acid, and it shows effective results for the elimination of Ni and V specially at lower acid concentrations. At high acid concentration, these columns remain effective mainly for the elimination of B by carbon-SDS column and the elimination of Ni by SDDC-carbon column.