摘要
通过研究四种改性生物质炭吸附重金属离子Pb（Ⅱ）和阳离子型染料亚甲基蓝的动力学效应、等温吸附效应、溶液初始pH效应和共吸附效应,探讨微波辅助加热在生物质炭氧化改性中的作用。结果表明,改性稻壳基生物质炭能够有效吸附Pb（Ⅱ）和亚甲基蓝,吸附容量显著高于初始生物质炭。Langmuir方程和Freundlich方程能很好地拟合改性稻壳基生物质炭吸附Pb（Ⅱ）和亚甲基蓝的等温数据（R2〉0.90）。改性生物质炭吸附Pb（Ⅱ）和亚甲基蓝的动力学研究显示,改性稻壳基生物质炭对Pb（Ⅱ）和亚甲基蓝的吸附主要发生在前2 h内,吸附过程符合伪二级动力学模型。随着溶液中pH的增大,Pb（Ⅱ）的去除率迅速增加,并在pH6时达到最大,亚甲基蓝的去除率在实验pH范围内也随pH缓慢上升,在pH为8~9时达到最大并逐渐趋于平衡。Pb（Ⅱ）和亚甲基蓝的共吸附效应表明,随着摩尔比值[MB/Pb（Ⅱ）]的增大,亚甲基蓝抑制了改性稻壳基生物质炭对Pb（Ⅱ）的吸附。微波加热硝酸氧化改性显著提高600℃热裂解生物质炭对Pb（Ⅱ）的吸附性能和300℃热裂解生物质炭对亚甲基蓝的吸附性能。
Biochars derived from various biomass feedstocks through slow pyrolysis/carbonization in an oxygen limited environment have been considered as promising low-cost and sustainable sorbents for organic and inorganic contaminants′ removal from aqueous solution. The related researches show that appropriate chemical modification of the pristine biochars will improve its adsorption capacity greatly. In this work, rice husk, a common agricultural by product, was chosen as a feedstock to prepare biochars through the pyrolysis at 600 ℃ and 300 ℃under oxygen-limited conditions. The resulting pristine biochars were oxidated by nitric acid via microwave heating and water-bath heating,respectively, to obtain four kinds of modified biochars. Then, the batch adsorption experiments of a cationic dye-methylene blue（MB）and a heavy metal ion-Pb（Ⅱ）onto the modified biochars were carried out to compare the adsorption effect of different biochars. The results indicated that the modified biochars exhibited greater adsorption capacity for Pb（Ⅱ）and MB than the pristine biochars, and the experimental data could be well fitted by the Langmuir and Freundlich isotherm model（R20.90）. Kinetic data showed that the adsorption of Pb（Ⅱ）and MB onto the modified biochars followed well with the pseudo-second order kinetic model, and the adsorption reached equilibrium in about 2 h. In the pH range of 2~6, the removal of Pb（Ⅱ）increased with the increase of solution pH and reached the maximum at pH 6. The removal rates of MB also increased with pH increasing from 4 to 8, and the maximum value was observed at pH 8. The co-adsorption experimental results showed that the adsorption of Pb（Ⅱ） onto modified biochars was greatly decreased with increasing molar ratio of MB/Pb（Ⅱ）, suggesting the possible competitive adsorption of MB and Pb（Ⅱ）onto biochars. Biochars modified with different heating methods had different adsorption performances for Pb（Ⅱ）and MB.
出处
《农业环境科学学报》
CAS
CSCD
北大核心
2016年第9期1773-1780,共8页
Journal of Agro-Environment Science
基金
国家自然科学基金重大研究计划培育项目(91543129)
关键词
生物质炭
等温吸附
动力学吸附
共吸附
biochar
adsorption isotherm
adsorption kinetics
co-sorption
