Synthetic and real wastewaters from match prodn. were treated with Al-Ca cements (up to 60 g/L) at pH 8.0-12.5 under stirring for 300 min (150 rpm) to remove SO42- ions (initial concn. 910-2475 mg/L). The gypsum precipitate was sepd. by sedimentation, filtration and centrifugation. The gypsum removal degree increased with increasing the cement dose and stirring time and showed a max. at pH 12.0 (near 100%).