Département de Génie Chimique, Université Laval, 1065 Avenue de la Médecine, Québec, QC, G1V 0A6, Canada.
Pyrovac Inc., 176-2 Rue Damase-Breton, Saint-Lambert-de-Lauzon, QC, G0S 2W0, Canada.
J Environ Manage. 2019 Jun 15;240:404-420. doi: 10.1016/j.jenvman.2019.03.110. Epub 2019 Apr 4.
In the present study, the effects of mild air oxidation of a biochar produced by the Pyrovac Inc. pyrolysis process, on the adsorption of lead(II) from synthetic wastewater under batch experimental conditions have been investigated. The adsorption experiments were performed under several conditions suggested by the response surface methodology, which allowed finding the optimal conditions, in order to maximize the adsorption capacity (Q(mgg)), as well as the extraction efficiency (E (%)). The optimal conditions of lead ions adsorption were as follows: pH = 5, agitation time = 300 min, adsorbent mass = 0.5 g (per 50 cm of solution), and lead initial concentration = 100gm, resulted in an adsorption capacity of 7.9 mg g. Equilibrium adsorption was then obtained by keeping pH and adsorbent mass at the optimal values and changing the lead initial concentration for a sufficient agitation time. Results showed that mild air oxidation increased the equilibrium adsorption capacity of biochar from 2.5 to 44 mg g. Oxidized biochar after equilibrium adsorption was submitted to SEM/EDX and XPS analysis. From SEM it was found that lead particles were distributed heterogeneously after adsorption. From XPS analysis, it was revealed that the external surface of oxidized biochar particles becomes saturated for the initial point of equilibrium diagram, obtained at lead initial concentration of 100gm, suggesting that for a higher concentration, the internal surfaces of particles participate in the cations adsorption. The participation of surface functional groups in the adsorption process showed that carbonyl, carboxylic, and aromatic rings of oxidized biochar were involved in the adsorption. This work suggests that the very simple process of mild air oxidation can be used instead of the usual costly chemical activation, in order to improve biochar cation exchange capacity.
在本研究中，研究了 Pyrovac Inc. 热解过程生产的生物炭经轻度空气氧化后，在批实验条件下对合成废水中铅（II）的吸附作用。吸附实验是在响应面法建议的几种条件下进行的，这使得可以找到最佳条件，以最大化吸附容量（Q(mgg))，以及萃取效率（E（%））。铅离子吸附的最佳条件如下：pH=5，搅拌时间=300min，吸附剂质量=0.5g（每 50cm 溶液），铅初始浓度=100gm，得到的吸附容量为 7.9mg g。然后通过保持 pH 和吸附剂质量为最佳值，并在足够的搅拌时间内改变铅的初始浓度，获得平衡吸附。结果表明，轻度空气氧化将生物炭的平衡吸附容量从 2.5 增加到 44mg g。平衡吸附后的氧化生物炭进行 SEM/EDX 和 XPS 分析。从 SEM 中发现，吸附后铅颗粒分布不均匀。从 XPS 分析中发现，氧化生物炭颗粒的外表面在初始平衡图点（在铅初始浓度为 100gm 时获得）变得饱和，表明对于更高的浓度，颗粒的内表面参与阳离子吸附。表面官能团在吸附过程中的参与表明，氧化生物炭的羰基、羧基和芳环参与了吸附。这项工作表明，轻度空气氧化这一非常简单的过程可以替代通常昂贵的化学活化，以提高生物炭的阳离子交换能力。
