Activated halloysite and roasted bentonite used for aero-filtration were added to granulated Fe concentrates for clinker prodn. in cement kilns. The contents of Al, Ca, K, Mg, Na, Si, Fe, Cu, Mn, Zn, Cd, Cr, Hg, Ni, Pb, Ti and Tl in the spent sorbents and in the Fe concs. were detd. The contents did not exceed allowable values.