This study investigated the impact of pyrolysis conditions on physical characteristics of date palm fronds biochars and their performances for aqueous uptake of anionic dyes—methyl orange (MO) and Eriochrome Black-T (EBT)—and cationic dyes—methylene blue (MB) and crystal violet (CV). Detailed characterization of the biochars revealed the formation of oxygen functionalities (C=O, C-O-C, and C-O), improved surface characteristics (surface area and pore volume) and high ash content at higher pyrolysis temperature and time. Biochar-derived date palm with a high surface area of 431.82 m²/g and a pore volume of 0.134 cm³/g was obtained at pyrolysis temperature and time 700 °C and 4 h, respectively. For all the four investigated dyes, the adsorption isotherm was mainly described by Redlich–Peterson isotherm model (R² > 0.95), while the adsorption kinetics well-fitted the pseudo-second order model. The biochar yielded fast dyes adsorption with maximum adsorption capacity for MB, EBT, MO, and CV dye of up to 206.61, 309.59, 163.132, and 934.57 mg/g at 200 mg/L dye concentration, respectively. The adsorption of cationic dyes was pH-independent indicating the involvement of pi–pi and chemical interactions. However, the uptake of the anionic dye was favorable at acidic conditions and was dominated by electrostatic interactions involving ion exchange and chemical reactions. The produced biochars exhibited excellent surface characteristics and enhanced adsorptive performance relative to other similar adsorbents. Thus, the direct pyrolysis of date palm fronds’ waste is a sustainable and economical approach of converting a huge quantity of wastes into excellent adsorbent for effective remediation of dye-contaminated water and wastewater.

中文翻译：

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亚甲基蓝，结晶紫，铬铁黑T和甲基橙染料在不同热解条件下生物炭衍生的枣棕叶废料上的吸附行为及机理

这项研究调查了热解条件对枣棕叶生物炭的物理特性的影响及其对阴离子染料甲基橙（MO）和Eriochrome Black-T（EBT）以及阳离子染料亚甲基蓝（MB）和结晶紫（CV）。生物炭的详细表征揭示了在更高的热解温度和时间下，氧官能团（C = O，COC和CO）的形成，改进的表面特征（表面积和孔体积）和高灰分含量。生物炭来源的枣椰子，具有431.82 m ² / g的高表面积和0.134 cm ³的孔体积/ g分别在热解温度和时间700℃和4小时下获得。对于所有四种研究的染料，其吸附等温线主要由Redlich-Peterson等温线模型（R ² > 0.95），而吸附动力学很好地拟合了伪二级模型。生物炭产生快速的染料吸附，在200 mg / L的染料浓度下，对MB，EBT，MO和CV染料的最大吸附容量分别高达206.61、309.59、163.132和934.57 mg / g。阳离子染料的吸附与pH无关，表明pi-pi的参与和化学相互作用。然而，在酸性条件下阴离子染料的吸收是有利的，并且主要由涉及离子交换和化学反应的静电相互作用决定。相对于其他类似的吸附剂，所生产的生物炭具有出色的表面特性和增强的吸附性能。从而，