The potentials of reverse osmosis (RO) in separation of soluble homogeneous catalysts from reaction products were studied. Two environmentally important liquid phase processes were considered : (A) detoxication of NO and H2S catalyzed by iron-containing phosphotungstenate heteropoly anion PW11FeII(H2O)O-39(5-) : 2NO+2O(2)+H2S-->2HNO(3)+S and (B) detoxication of the water soluble sulfides catalyzed by the sodium salt of tetra(sulfophthalocyanine)cobalt(II) : S2-+O-2-->(S, SO32-, SO42-, S2O32-) For reaction (A), the RO retention of the NO3- product was found to decrease with the concentration of the heteropoly anion catalyst, reaching negative values, whereas the retention of the catalyst amounted to 99 %. Due to the negative retention of the nitrate ions and high positive retention of the catalyst, their efficient separation was achieved. For reaction (B), RO allowed to retain the catalyst almost completely (retention exceeded 99.9 %), while the products (sulfur-containing anions) exhibited markedly lower retentions. For both reactions, the structure and activity of the catalysts remained unchanged after the RO separation, thus enabling their multifold re-use.