向日葵制活性炭对亚甲基蓝的吸附研究

Research on adsorption of methylene blue on activated carbon prepared from sunflower

含有亚甲基蓝(MB)的废液直接排放会造成严重的水体污染。为研究生物质活性炭对MB的吸附性能,以农业废弃物向日葵为原料、磷酸(H3PO4)为活化剂,制备粉状活性炭(PAC)和块状活性炭(BAC),并研究PAC对MB的吸附性能。利用比表面积测试(BET)、X射线光电子能谱(XPS)、X射线衍射(XRD)、红外光谱(FT-IR)和扫描电镜(SEM)等方法解析活性炭的孔结构和表面特性。结果表明:活性炭前驱体的形状对活性炭的微观结构有较大的影响。PAC比BAC具有更大的比表面积(分别为701.95 m^(2)/g和566.49 m^(2)/g)和总孔体积(分别为2.23 cm^(3)/g和1.04 cm^(3)/g);PAC和BAC的平均孔径分别为7.31 nm和12.66 nm,均具有介孔材料的结构特性。两种活性炭表面均分布着丰富的含氧官能团和大量疏松的无定形碳,而存在的偏磷酸盐对孔隙起到支撑作用,这为MB的吸附提供了更多的活性位点和吸附通道。在25℃、pH为8、PAC用量为50 mg条件下,PAC对100 mL质量浓度为200 mg/L的MB溶液的吸附效果最好,吸附率达到72.2%。吸附过程符合伪二级动力学模型、颗粒内扩散模型和Langmuir等温吸附模型。

Direct discharge of waste liquid containing methylene blue(MB)will cause serious water pollution.In order to study the adsorption performance of activated carbon for methylene blue,agricultural waste sunflower was used as raw material and H3PO4 as activator to prepare powdered activated carbon(PAC)and block activated carbon(BAC),and the adsorption performance of PAC to MB was studied.The hole structure and surface properties of activated carbon were analyzed by means of surface area test(BET),X-ray photoelectron spectrum(XPS),X-ray diffraction(XRD),infrared spectroscopy(FT-IR)and scanning electron microscopy(SEM).The research results showed that the shape of activated carbon precursor had great influence on the microstructure of activated carbon.PAC had larger specific surface area and total pore volume than BAC(701.95,566.49 m^(2)/g and 2.23,1.04 cm^(3)/g,respectively).The average pore size of PAC and BAC was 7.31 nm and 12.66 nm,respectively.Both PAC and BAC had the structural characteristics of mesoporous materials.There were abundant oxygen-containing functional groups and a large number of loose amorphous carbon on the surface of both activated carbons,and the existing metaphosphate played a supporting role on the pores,which provided more active sites and adsorption channels for the adsorption of MB.The results of the adsorption experiment showed that the maximum adsorption rate was 72.2%under the conditions of 100 mL MB solution with a concentration of 200 mg/L,pH of 8 and PAC dosage of 50 mg at 25℃.The adsorption process was conformed to the pseudo-second-order kinetic model,the intra-particle diffusion model and the Langmuir isotherm adsorption model.