Purification and defibering of a Chinese sepiolite

• Natural sepiolite was purified and the content was elevated from 42 wt.% to 91 wt.%.
• Microwave assisted acid treatment was an effective purification process.
• Lyophilization process effectively dissociated the crystal bundles of sepiolite.
• HDTMA was a suitable modifier for improving the dispersion of sepiolite.

To extend the utilization of the low-grade Human (China) sepiolite, the purification of the ore is the prerequisite for all applications. Sepiolite accompanied by quartz and calcite was effectively purified via sedimentation method and the microwave assisted acid treatment. The influence of treatment time on sepiolite purity and structure was qualitatively studied based on XRD and FESEM. Sepiolite had been successfully purified and the content was elevated from 42 wt.% to more than 90 wt.%. Microwave assisted acid treatment demonstrated to be an effective purification process by removing carbonates without affecting sepiolite length. Furthermore, both physical method of lyophilization and chemical method of surface modification were proposed as simple alternatives to defibering acid-treated sepiolite crystal bundles. The effects of freezing time and surfactant chain length on the disaggregation state, micro-structure and properties of treated sepiolite were analyzed comparatively using FESEM, TEM and BET. Results of FESEM and TEM indicated that the crystal structure of sepiolite was not changed after freezing at − 50 °C for 12 h or modification with hexadecyl trimethyl ammonium bromide (HDTMA), but the aggregates were effectively disaggregated. The BET specific surface areas of the dispersed sepiolite rods obtained by these two methods increased to 144.3 and 93.1 m2/g, respectively, showing good agreement with the perfect dispersion of sepiolite fibers.