The effect of acid and thermal treatment on the natural diatomite characterizations

The characterizations of natural diatomite from Birjand deposit (Iran) were studied such as chemical compositions, specific surface area, total pore volume, pore size distribution and XRD. The diatomite that was treated only with sulfuric acid displayed a larger surface area, expanded total pore volume and increased pore size in comparison with both washed natural diatomite with deionized water and the diatomite treated with sulfuric acid then calcinated at 550°C. The specific surface area and total pore volume were increased 46.63% and 71.40%, respectively. The results showed that the diatomite samples were composed of cristobalite, quartz and feldspar phases. Acid treatment and then calcination at 550°C changed the Si/Al ratio and grew the crystallite size. BJH with DFT analysis showed that the diatomite samples had very disordered micro/mesoporous pore networks. The pore size distribution of the diatomite samples were from 1.4100 nm. The isotherm of the samples were type IV and showed a long hysteresis loop that resembled the H3 type on the basis of the IUPAC classiï‌cation. Therefore, the diatomite that was treated only with 3M H2SO4 or treated with sulfuric acid then calcinated at 550°C can be to serve as a catalyst support or an adsorbent.