Diatomite was treated with aq. NaOH, HCl, EDTA and NaOH+NH(4)HCO(3) solns. at 100 degrees C for 3 h and used for adsorption of BuNH(2) and methylene blue from their aq. solns. and for catalytic decompn. of iso-PrOH at 350 degrees C for 4 h. The modification resulted in an increase of the adsorption capacity of diatomite and a decrease in iso-PrOH conversion.