A carbon silica composite prepared from water slurry coal gasification slag

A large number of coal water slurry gasification slag (CWSGS) was discarded annually in China due to the promotion of clean coal technology. The fine slag (FCWSGS) is abundant of silicates and unburned carbon. This research investigated the preparation of a porous carbon-silica composite (CSC) from FCWSGS using KOH activation followed by hydrochloric acid leaching. The orthogonal experiments showed that optimum parameters for preparing CSC were: activating at 1173 K for 1 h, hydrochloric acid concentration of 20%, leaching at 363 K for 30 min. The acid concentration was remarkable for total surface area and acid leaching temperature was remarkable for both total surface area and total pore volume while had few effect on micropore formation. The formation of micropore is a diffusion controlled process and the formation of mesopore is a chemical reaction controlled process. When the KOH/FCWSGS was 3, the prepared CSC had a BET surface area of 1347 m2/g, a total pore volume of 0.69 cm3/g, the mesoporosity of 81% and an average slit-liked pore diameter of 3.44 nm.