Institute of Agricultural Resources and Environment, Guangdong Academy of Agricultural Sciences, Guangzhou 510640, China; Department of Renewable Resources, University of Alberta, Edmonton, Alberta T6G 2E3, Canada.
Department of Renewable Resources, University of Alberta, Edmonton, Alberta T6G 2E3, Canada; Department of Rural Construction Engineering, Jeonbuk National University, Jeonju, Jeollabukdo 57896, Republic of Korea.
Sci Total Environ. 2020 Apr 10;712:136538. doi: 10.1016/j.scitotenv.2020.136538. Epub 2020 Jan 8.
Biochar is a promising material for efficient removal of toxic metals from wastewater to meet standards for discharge into surface water. We characterized adsorption behaviour of willow (Salix alba) wood (WW) and cattle manure (CM) and their biochars, willow wood biochar (WWB) and cattle manure biochar (CMB), and elucidated the mechanisms for the removal of Ni(II), Cu(II) and Cd(II) from aqueous solutions. The kinetic adsorption suggests that the adsorption of Ni(II), Cu(II) and Cd(II) by feedstock and their biochars was controlled by mass transport, and chemisorption also played a role in the adsorption process. The Elovich model also well described the adsorption kinetics for WW and CM (R > 0.92), indicating that heterogeneous diffusion was the mechanism. The Sips isotherm model fitted best (R > 0.98) for Ni(II), Cu(II) and Cd(II) adsorption by the feedstocks and their biochars, indicating that both monolayer and multilayer adsorption played roles on the heterogeneous surfaces of the four adsorbents. The WWB had a higher while the CMB had a lower adsorption capacity than their respective feedstock due to the presence of abundant -COOH functional group on WWB surface to interact with Ni(II), Cu(II) and Cd(II) to form surface complexes. The higher specific surface area and lower pH of point of zero charge (PZC) of WWB were other contributing factors for its greater removal capacity. Therefore, we conclude that proper feedstocks need to be selected to produce biochars that are efficient for the removal of toxic metals from wastewater.
生物炭是一种很有前途的材料，可以有效地去除废水中的有毒金属，使其达到排入地表水的标准。我们对柳树（Salix alba）木材（WW）和牛粪（CM）及其生物炭、柳树木材生物炭（WWB）和牛粪生物炭（CMB）的吸附行为进行了表征，并阐明了它们从水溶液中去除 Ni(II)、Cu(II)和 Cd(II)的机制。动力学吸附表明，Ni(II)、Cu(II)和 Cd(II)在原料及其生物炭上的吸附受质量传递控制，化学吸附也在吸附过程中起作用。Elovich 模型也很好地描述了 WW 和 CM 的吸附动力学（R>0.92），表明异质扩散是该机制。Sips 等温线模型最适合（R>0.98）描述 Ni(II)、Cu(II)和 Cd(II)在四种吸附剂上的吸附，表明单层和多层吸附都在四个吸附剂的异质表面上起作用。由于 WWB 表面存在丰富的-COOH 官能团，与 Ni(II)、Cu(II)和 Cd(II)相互作用形成表面络合物，因此 WWB 的吸附能力高于其原料，而 CMB 的吸附能力低于其原料。WWB 具有较高的比表面积和较低的零电荷点（PZC）pH 值，这也是其去除能力较强的其他因素。因此，我们得出结论，需要选择合适的原料来生产高效去除废水中有毒金属的生物炭。
