以臭氧为活化剂,炭化的米糠为原料制备出活性炭。采用氮吸附、SEM-EDAX 和FT-IR对样品进行表征。活性炭的比表面积由活化前的20 m2/g增加到380 m2/g。在臭氧活化过程中,吸附在炭材料上的二氧化硅变疏松,从而导致碳逸出。臭氧同时以氧分子和原子形式存在于炭表面。氧原子,作为强氧化剂,将炭表面氧化成酸性官能团如羧基、酮基和酚基。采用该活性炭吸附Cr (VI)离子,Cr (VI)离子的最大去除率(94%)的条件为：pH值2.0、浓度100 mg/L、吸附量0.2 g,时间2.5 h及转速300 r/min。采用吸附平衡和动力学模型探讨吸附机理,结果表明,吸附等温线符合Freundlich方程,吸附速率符合准二级动力学方程。吸附是自发的放热反应,可能与NaOH脱落而恢复Cr和碳有关。
Activated carbon ( AC) was prepared from carbonized rice husks using ozone as an activating agent. The AC was char-acterized by nitrogen adsorption, SEM-EDAX and FT-IR. The Brunauer-Emmett-Teller surface area of the carbons was increased from 20 to 380 m2/g by the activation. It was observed that the silica attached to the carbonaceous material is loosened, leading to a release of carbon during the ozone activation. Ozone exists as both molecular and atomic oxygen on the surface of carbon. Atomic oxygen, as a powerful oxidizing agent, oxidizes the carbon surface into acidic functional groups such as carboxylic, ketonic and phenolic. The rice husk AC was used for the adsorption of Cr (VI) ions. A maximum removal percentage (94%) of Cr (VI) ions was obtained for a 100 mg/L aqueous solution at the optimized conditions of pH value of 2. 0, adsorbent dosage of 0. 2 g, time of 2. 5 h and stirring speed of 300 r/min. Adsorption equilibrium and kinetic models were used to investigate the adsorption mecha-nism. It was found that the adsorption isotherms were well fitted by the Freundlich equation. The adsorption rate follows pseudo sec-ond order kinetics and the adsorption is spontaneous and exothermic. It is possible to recover Cr and carbon by NaOH stripping.
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