Dissolution behavior of steam generator deposit in oxalic acid

Abstract The dissolution behavior of simulated deposit Fe 3 O 4 and steam generator sludge in oxalic acid solution was studied by methods of SEM, XRD, XRF and ICP-OES. The electrochemical properties of simulated deposit chemically modified electrodes in oxalic acid solution were tested under a three-electrode system to guide the optimization of chemical cleaning process. The results indicate that oxalic acid chemical cleaning agent could effectively remove iron oxidation deposits and harmful elements such as Cu, Pb and Al in SG sludge. With the increase of oxalic acid concentration, the solubility of the simulated deposit is enhanced. But when the oxalic acid concentration reached 5%, the dissolution process of SG sludge will change into the deposition process after reaching a brief equilibrium, and FeC 2 O 4 (H 2 O) 2 crystals will be formed. The solubility of simulated deposit in the oxalic acid is stronger than that of the sludge, which is related to the particle size difference between the simulated deposit and the SG sludge, as well as the influence of Cr, Mn, Ti, Ni, Mg and other elements doped in the oxide lattice of the sludge. The electrochemical reaction process of simulated deposit chemically modified electrode in oxalic acid solution is adsorption controlled.