紫外辐照引入含氧官能团对生物炭吸附气体和水中苯的影响

以椰壳为原料制备生物炭,采用365 nm紫外光辐照增加吸附剂表面含氧官能团,探究其对生物炭吸附气体和水中苯的影响.理化表征和吸附实验结果表明,生物炭表面含氧官能团增加后,对气体中苯的吸附量提高9.25倍,而对水中苯的吸附量却降低14.64%.生物炭对气体中苯的吸附过程符合Elovich动力学模型,而对水中苯的吸附过程符合准二级动力学模型.含氧官能团的引入使生物炭对气体和水中苯的等温吸附过程从符合Freundlich模型变为符合Langmuir模型.Weber-Morris模型分析认为,增加含氧官能团,可增强生物炭对气体中苯的表面吸附速率,却阻碍了苯从水中向吸附剂颗粒内扩散的过程,水分子与苯竞争吸附是导致生物炭对水中苯吸附量降低的主要原因.

Effects of increased oxygen-containing functional groups induced by ultraviolet irradiation on biochar adsorption behaviors of benzene in air and water

Coconut shell based biochar was irradiated by UV light at wavelength of 365 nm to investigate the effects of surface oxygen-containing functional groups of biochar on its adsorption behaviour to benzene in air and water. The physicochemical properties of pristine and modified biochars were measured and the batch experiments were carried out. The results showed that the sorption capacity of modified biochar to gaseous benzene was increased by 9.25 times comparing with the initial biochar. However, the sorption capacity to aqueous benzene was reduced by 14.64%. Elovich equation best fitted the absorption process of gaseous benzene on biochar, whereas the pseudo-second-order model fitted the dynamics of aqueous benzene adsorption better. With increasing of oxygen-containing functional groups on biochar, the adsorption isotherms of benzene both in air and water onto biochar were better fitted by the Langmuir model than by the Freundlich model. It suggests that the oxygen-containing functional groups could enhance adsorption rate of gaseous benzene on biochar but hinder the intraparticle diffusion process of aqueous benzene on sorbent. The declining of adsorption capacity of biochar to benzene in aqueous solution could be mainly attributed to the existing competitive adsorption between water and benzene.