Influence of boric acid on the speciation of iron (III) in aqueous solutions

During the work, the speciation of iron (III) was studied at the concentration of ~ 1∙10 –5 mol/dm 3 in aqueous solutions in the presence of boric acid at a concentration of 5–20 g/dm 3 in a wide pH range using ion exchange, ultrafiltration and centrifugation methods. The regions of existence of ionic and nonionic forms of iron (III) were determined by ion exchange in solutions with different boric acid concentrations. Experimental data have shown that the pH of the onset of iron (III) colloid formation shifts in the presence of boric acid. The formation of complex compounds of iron (III) with polyborate ions in the neutral – slightly alkaline pH region was established by ultrafiltration and centrifugation. As shown in the paper, the increase in the concentration of boric acid in solution leads to the increase in the region of existence of the supposed complexes. The identified features of the behavior of iron (III) in solutions containing boric acid determine the possibility of using ion exchange and membrane separation methods for purifying solutions. Information about the physical-chemical properties of various metal-ions can provide optimal conditions for the purification of liquid radioactive waste at various nuclear industry facilities.