The hydrophobic SiO 2 aerogel was prepared by using coal gangue as the starting material—which is viewed as waste in most coal mining and preparation plant—via ambient pressure drying through sol-gel method. The effects of different temperature, time to keep the temperature,vary in mass ratio of coal gangue to sodium hydroxide on the leaching ratio of SiO 2 from coal refuses are discussed in this paper. Results showed that the leaching ratio of SiO 2 extracted from gangue will be made up to 35.23% compared with the other tests on the condition that the temperature is given 750°C, holding time 2h, the value of ratio of coal gangue to sodium hydroxide 1:0.8, concentration of NaOH 20%. Trimethylchlorosilane (TMCS) is used as modifier to obtain hydrophobicity through solvent exchange and surface modification. We achieved SiO 2 aerogel with low density of 0.2559g/cm 3 , high porosity 88.97%,Strong hydrophobicity (contact angle with water 140.61 。 ) respectively, which demonstrated that the final product exhibits excellent property. Differences among SiO 2 aerogel properties were discussed between industrial sodium silicate as precursor and sodium silicate drew from coal gangue as precursor. Results revealed that the the latter is better than the former on properties .Our work provided a potential way to synthetize high value-added product from abandoned by-product coal gangue.
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Zhu et al. (2014) studied this question.