The regeneration of the ceramic filter medium in the dewatering of iron ore enables the use of the medium for much longer periods in comparison to traditional filter cloths. The regeneration is commonly a combination of several techniques, of which one is the acid washing of the medium. Despite being effective against iron oxides, the phenomena related to the acid washing of the ceramic filter medium with oxalic acid have so far been less extensively published. The aim of this study was to investigate the dissolution of iron oxide particles from the surface of the filter medium and the consequent changes in the performance and in the structure of the medium. The dissolution of the particles was found to exhibit some kind of a steady state dependent on temperature but not so much on the acid concentration. Changes in permeability as well as in pore size were found to take place even after the dissolution of the particles had ceased. 1. Introduction The final dewatering of a magnetite concentrate can be performed with ceramic capillary action disc filters. During operation, magnetite particles are adhered to the surface of the filter medium causing the decline of filtrate flux. The ceramic filter medium, however, is robust enough to withstand both mechanical and chemical regeneration, and, consequently, the performance of the filter medium can be restored. The regeneration of the ceramic filter medium in capillary action disc filters incorporates several operations: (1) backwashing, (2) ultrasonic cleaning, and (3) acid regeneration. In iron ore applications, oxalic acid can be used for the regeneration as it has been shown to efficiently dissolve iron oxides [1–9]. Although the regeneration of ceramic membranes fouled by oxide particles has been receiving an increasing attention in cross flow filtration [10–13], published research on the regeneration of the ceramic membrane used for the dewatering of mineral concentrates is scarce. Even the fundamental effects of oxalic acid regeneration, currently used for several ceramic disc filters in iron ore dewatering, on the filter medium are fairly unknown and make it challenging to develop the regeneration process. The further development of the process, however, requires a deeper understanding of the phenomena underlying the acid treatment of the filter medium. The aim of this study was to provide more insight into the dissolution of particles during the regeneration and into what are the actual changes in the filter medium as a result of the regeneration. The experiments were done with samples from a full
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