磷酸中添加剂对核桃壳活性炭性能的影响

采用磷酸活化法制备核桃壳颗粒活性炭，研究了在磷酸浸渍液中加入不同种类和含量添加剂对活性炭性能的影响。以亚甲基蓝和碘吸附值表征活性炭的吸附性能，并对活性炭的孔结构参数、机械强度和微晶结构进行了测试分析。结果表明：在磷酸中分别添加柠檬酸、柠檬酸钠、硼酸和糖精浸渍处理核桃壳原料，所得活性炭的亚甲基蓝吸附值都得到提高，而碘吸附值降低，说明添加剂促使活性炭中的微孔扩大为中孔。其中，添加0.5%的柠檬酸钠得到最佳的亚甲基蓝和碘吸附值，分别达到236.5和744.1 mg/g。此外，磷酸中添加1%硼酸后得到的活性炭结构中含坚固的炭微晶，起到了增强孔结构的作用，机械强度为85.8%；而添加1%糖精得到的活性炭中的炭微晶几乎全部发生了石墨化转变，生成质软的石墨，使强度下降，机械强度仅为80.1%；添加0.5%柠檬酸钠的活性炭由于发达的孔隙结构且没有炭微晶的加固而强度较低(82.5%)。

Effects of Additives in H3PO4 Solution on Properties of Activated Carbon from Walnut Shell

Activated carbons were prepared from walnut shell by H₃PO₄ activation and the effects of adding different kinds and contents of additives to H₃PO₄ solution on the properties of activated carbons were investigated. The adsorption property was characterized by methylene blue and iodine adsorption values. The pore structure parameters, mechanical strength and graphite microcrystalline of activated carbon were tested. When the activated carbons were prepared by walnut shell immersed in H₃PO₄ solution with the addition of citric acid, sodium citrate, boric acid and saccharin, respectively, the methylene blue adsorption values increased, and the iodine adsorption values and the mechanical strength decreased. This meant the additives promoted the expansion of micropores of activated carbons to mesopores. Adding 0.5% sodium citrate in H₃PO₄ solution, the activated carbon with the maximum methylene blue and iodine adsorption values was gained, which were 236.5 and 744.1 mg/g, respectively. In addition, the structure of activated carbon obtained by adding 1% boric acid into H₃PO₄ solution contained microcrystalline carbon, which was hard and played a role in enhancing pore structure and the mechanical strength was 85.8%. However, the microcrystalline carbon in the activated carbon obtained by adding 1% saccharin almost transformed graphitization transformation, resulting in soft graphite, thus the strength decreased to 80.1%. The activated carbon with 0.5% sodium citrate had low strength(82.5%) because of its rich pore structure without microcrystalline reinforcement.