A novel and complete process for iodine extraction and recovery from industrial wet-process phosphoric acid based on chemical oxidation and solvent extraction

Abstract

Due to their copious availability and broad applicability, iodine recovery from numerous sources, such as byproducts of various industrial processes, has attracted attention. To meet growing market demand for iodine as well as to accomplish long-term management of iodine resources, phosphate rocks and their derivatives were discovered as a possible source of iodine. As phosphoric acid is produced in significant quantities each year more than 20 million tons the extraction of iodine, a byproduct of the wet processing of phosphoric acid, is crucial. This research aims to develop a pre-oxidation and solvent extraction-based method for recovering high purity iodine from wet phosphoric acid (SX). For this purpose, the effects of operating variables, such as: time, acidity, dose of the oxidant, temperature, volume ratio, and the concentration of stripping solution have been studied. Using 30% H2O2 as an oxidant, all the iodides ions present in wet phosphoric acid was converted into elemental iodine. The iodine was then extracted and stripped quantitatively using pure kerosene and 0.02 M sodium sulfite at ratios (O:A) of 1:2 and 1:1, respectively. The resulting iodine precipitate was subjected to several analyses, including iodometric titration, XRD, and ICP-OES, which confirmed its purity to be 99.9%. Finally, a flowchart process for both recovering and reducing the loss of iodine from wet phosphoric acid was developed without interfering with the normal fertilizer production route.