Sulfur Removal From Low-Grade Turkish Kaolin Clay

This study investigated the effects of NaOH direct leaching for sulfur removal from a kaolin ore from the Balıkesir region, Turkey. Characterization studies were undertaken before sulfur removal studies to enlighten the structure and originate the source of sulfur. The characterization studies revealed that the ore was mainly composed of quartz, with sulfur originating from alunite minerals with opal inclusions. The leaching process was tested under varying NaOH concentrations (1.5–2 M), temperatures (95 ± 2°C), and durations (2 h) in temperature-controlled closed systems to maintain consistency. Results demonstrated complete (100%) sulfur removal from alunite under optimal conditions. However, significant mass losses (18.15%–45%) occurred because of the dissolution of kaolinite along with alunite, indicating the method's effectiveness in sulfur removal but also its potential drawbacks for kaolinite retention.