The Preparation Of Clay/Activated-carbon Nanocomposites And Its Adsorption Properties Of Organic Pollutants

The clay/activated-carbon composite was prepared by the junction of hydrothermal carbonization and activation p. We used clay minerals as template and cellulose as carbon source which are abundant in nature. The studies aimed at the activation process which influenced the development of pore structure and surface area of clay/carbon composite. And the adsorption for methylene blue and phenol were also investigated. The main conclusions were listed as follows:1) The palygorskite and cellulose were treated at 220℃ by hydrothermal method. The hydrothermal product (palygorskite/hydrochar) was obtained. Then the composite was mixed with ZnCl2 which acted as activating agent, and heated at given temperature. Activation parameters, such as temperature and impregnation ratio was investigated. The results show that the surface area of composite was improved significantly by ZnCl2 activation, and the pore diameter was controllable. The maximum value of surface area was up to 1201 m2/g, when impregnation ratio was 1:1 and activation temperature was 450℃. Adsorption study of methylene blue showed that the maximum adsorption capacity on the activated composite was 351 mg/g, which was far higher than that of untreated palygorskite/carbon (89 mg/g). The adsorption condition was optimized.2) The palygorskite/activated carbon was also prepared by one step calcined method with ZnCl2 as activating agent. The result showed that ZnCl2 can promote the carbonization and activation of cellulose at heating process. The obtained carbon product coated with palygorskite. The ultimate composite has high surface area with numerous mesopores and micropores. The highest surface area was up to 1478 m2/g. The maximum adsorption capacity of methylene blue on the obtained composite 346 mg/g, which was higher than that of palygorskite (63 mg/g) and commercial activated carbon (318 mg/g).3) The halloysite/carbon composite was prepared by hydrothermal method at 220℃, using halloysite as template and cellulose as carbon source. Then the composite was heated at different temperature (400-1200℃) and N2 atmosphere. The composite was also treated with acid after heating in air. The composite was firstly heated at 400,500, 600℃ at air, respectively. Then it was treated with HCl solution of 5 mol/L. The studies showed that heat treatment and heat-acid treatment can both improve the surface area of composite. The highest value reached 506 m2/g, which was higher than that of untreated composite (44 m2/g). The removal rate of phenol was improved from 52% to 99%.4) The high surface area adsorbent was prepared by using spent bleaching earth as precursor, ZnCl2 or KOH as activating agent. The immersion ratio of ZnCl2 activation was in the range of 0.5-2. The activation temperature was fixed at 500℃ and activation time was 1 h. The surface area of activated product was in the range of 250 to 300 m2/g and the yields were all higher than 50%. The immersion ratio of KOH activation was 0.5-3. The temperature was 750℃ and time was 1 h. The surface area was at 351-574 m2/g. The spent bleaching earth regenerated after activation and its surface area was improved apparently.