The capacity and underlying mechanism of hydrochars derived from commercial D-glucose and wasted orange peels (designated as pristine-hydrochars) and further modified with nitric acid (designated as oxidized-hydrochars) to adsorb methylene blue were investigated. Both pristine- and oxidized-hydrochars were characterized by scanning electron microscopy, Brunauer–Emmet–Teller-specific surface area, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and mass titration. The maximum methylene blue adsorption capacity at 30°C estimated by the Langmuir model was found to follow the order: mGH (246 mg/g) > mOPH (107 mg/g) > OPH (59.6 mg/g) > GH (54.8 mg/g). Six adsorption mechanisms were elucidated, in which the electrostatic interaction and hydrogen bonding were identified as the primary methylene blue-hydrochar adsorptive interaction; furthermore, because the nitric acid modification process enhanced oxygen- and nitrogen-containing functional groups and unsaturated bonds on the surface of oxidized-hydrochars, the π–π and n–π interaction became minor pathways for methylene blue adsorption onto oxidized-hydrochars. Our results suggest that modified hydrochars could be used as environmentally friendly adsorbents alternative to activated carbon in dealing with methylene blue contamination in aqueous solutions.

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硝酸氧化在碳氢化合物表面吸附亚甲基蓝的影响：吸附机理比较

研究了衍生自商业 D-葡萄糖和废弃橙皮的加氢碳（称为原始加氢碳）并用硝酸进一步改性（称为氧化加氢碳）以吸附亚甲蓝的能力和潜在机制。通过扫描电子显微镜、Brunauer-Emmet-Teller 比表面积、傅里叶变换红外光谱、X 射线光电子能谱和质量滴定对原始和氧化的水炭进行了表征。发现由朗缪尔模型估计的 30°C 最大亚甲基蓝吸附容量遵循以下顺序：mGH (246 mg/g) > mOPH (107 mg/g) > OPH (59.6 mg/g) > GH (54.8 mg) /G）。阐明了六种吸附机制，其中静电相互作用和氢键被确定为主要的亚甲基蓝-氢碳吸附相互作用；此外，由于硝酸改性过程增强了氧化氢碳表面的含氧和氮官能团和不饱和键，π-π 和 n-π 相互作用成为亚甲基蓝吸附到氧化氢碳上的次要途径。我们的研究结果表明，在处理水溶液中的亚甲基蓝污染时，改性氢化碳可用作替代活性炭的环保吸附剂。π-π 和 n-π 相互作用成为亚甲蓝吸附到氧化氢碳上的次要途径。我们的研究结果表明，在处理水溶液中的亚甲基蓝污染时，改性氢化碳可用作替代活性炭的环保吸附剂。π-π 和 n-π 相互作用成为亚甲蓝吸附到氧化氢碳上的次要途径。我们的研究结果表明，在处理水溶液中的亚甲基蓝污染时，改性氢化碳可用作替代活性炭的环保吸附剂。