This study investigates the methylene blue adsorption by ryegrass by-products. Milled ryegrass straw (Lolium multiflorum Lam.), treated straw, and the biochar produced from the straw with chemical activation with sodium hydroxide solution were used as adsorbent materials. To obtain the biochar, the pyrolysis was performed in a tubular reactor with nitrogen flow at 623 K. The characterization of all the adsorbents was realized analyzing the real density, bulk density, particle diameter, proximate analysis, thermogravimetric analysis, X-ray diffraction, and scanning electron microscopy. Kinetic studies and adsorption isotherms were evaluated with models fit predicted in the literature. The biochar showed a well-developed porous structure. In the treated straw, there occurred a degradation of compounds such as hemicelluloses and lignin, which gave the modification in the surface of the material. For the kinetic studies, the pseudo-first-order, pseudo-second-order, and Avrami models presented a good fit. For the adsorption isotherms, the Sips model provided the maximum adsorption capacity to the milled straw (28.7 mg/g) and treated straw (67.19 mg/g). The most promising results were obtained by the treated straw, with high efficiency in the removal of the methylene blue dye from the solution, reaching values higher than 99%.

中文翻译：

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用黑麦草秸秆去除水溶液中的亚甲蓝

这项研究调查了黑麦草副产物对亚甲基蓝的吸附。磨碎的黑麦草秸秆（黑麦草）Lam。，处理过的秸秆和由秸秆制成并经氢氧化钠溶液化学活化的生物炭用作吸附材料。为了获得生物炭，在具有623 K氮气流量的管式反应器中进行热解。通过分析实际密度，堆积密度，粒径，近似分析，热重分析，X射线衍射，和扫描电子显微镜。动力学研究和吸附等温线用文献中预测的模型进行评估。生物炭显示出发达的多孔结构。在经过处理的秸秆中，半纤维素和木质素等化合物发生降解，从而使材料表面发生了改性。对于动力学研究，伪一阶，伪二阶，和Avrami模型很合适。对于吸附等温线，Sips模型为研磨后的秸秆（28.7 mg / g）和处理过的秸秆（67.19 mg / g）提供了最大吸附容量。经过处理的秸秆获得了最有希望的结果，从溶液中去除亚甲基蓝染料的效率很高，达到高于99％的值。