人居生活废弃物生物黑炭对水溶液中Cd2+的吸附研究

以人居生活废弃物生物黑炭为材料,探讨生物黑炭对Cd2+的吸附动力学及热力学特性,通过平衡吸附法研究吸附时间、Cd2+初始质量浓度、吸附剂投加量、溶液pH值以及黑炭粒径对Cd2+吸附率的影响.结果表明,吸附时间为2h时基本达到吸附平衡,准二级动力学方程能很好地描述生物黑炭对Cd2+的吸附过程.Langmuir模型能较好地描述生物黑炭对Cd2+的等温吸附过程,根据该模型模拟得到25℃条件下Cd2+最大吸附量为6.22mg·g-1.Cd2+去除率随生物黑炭投加量的增加而增大；生物黑炭对Cd2+吸附量随其粒径减小而增大；溶液初始pH值为4.0～7.5时,pH值变化对Cd2+吸附量的影响不显著.采用人居生活废弃物生物黑炭去除水溶液中Cd2+时,控制溶液Cd2+初始质量浓度30mg·L-1,粒径小于0.25 mm,投加水平8g·L-1,反应温度25℃,反应时间1～2h,Cd2+去除率可达80％.人居生活废弃物生物黑炭可以作为去除污染水体中Cd2+的吸附剂.

Adsorption of Cadmium in Solution by Biochar From Household Biowaste

Biochar produced via pyrolysis of household biowaste was used as an adsorbent in an experiment to study kinetics and thermodynamics of its adsorption of Cd2+ in solution and to explore effects of incubation time,initial Cd2+ concentration,adsorbent dosage,solution pH as well as particle size of biochar on its Cd2+ adsorption rate with the equilibrium adsorption method.Results show that the adsorption basically reached equilibrium after 2 h and the process could be well described with the pseudo second order dynamic equation.The adsorption curves followed an isothermic adsorption model,which could be well described with the Langmuir model.The Cd2+ adsorption peaked at 25 ℃,reaching 6.22 mg·g-1 as simulated with the Langmuir model.Cd2+ removal rate increased with increasing dosage of biochar and decreasing particle size of biochar.The effect of pH on Cd2+ adsorption capacity was not obvious when initial pH of the solution was 4.0-7.5.When biochar is used to remove Cd2+ from wastewater,it is advisable to control the initial Cd2+ concentration at 30 mg·L-1,particle size of the biochar at <0.25 mm,dosage of the biochar at 8 g·L-1,reaction temperature at 25 ℃,and duration of the reaction at 1-2 h.In this case,the Cd2+ removal rate can be as high as 80%.This indicates that biochar made from household biowaste can be as adsorbent to remove Cd2+ in polluted water.