Rhodium containing homogeneous catalysts are important in many industrial processes such as hydroformylation and hydrogenation, but their high cost means that efficient separation from product streams is essential. However, complete recovery of low metal concentrations is difficult, with ion-exchange being the best method. The difficulty is to find the best material for optimum binding - if the ligand's binding capacity is too strong, desorption becomes very difficult. It has now been shown that silica based chelating ion exchangers containing amines or polyamine functionalities (Kramer J et al, Chem Commun, 2001, 2420) give excellent recovery of rhodium ions from waste streams in homogenous catalysis.