In this work, an alternative utilization of agro-industrial waste coconut endocarp (Cocos nucifera L.) as raw material for the synthesis of magnetic adsorbent aiming the phenol removal is proposed. The synthetized adsorbent, denominated magnetic activated carbon (MAC), was prepared by coprecipitation of cobalt ferrite (CoFe₂O₄) onto activated carbon surface obtained by carbonization of coconut endocarp. Characterization of MAC was carried out by point of zero charge (PZC), Brunauer, Emmett, and Teller (BET) surface area, scanning electron microscopy (SEM), x-ray fluorescence (XRF), Fourier transform infrared spectroscopy (FTIR), x-ray diffractometry (XRD) analysis, and magnetization curves. Adsorption experiments were performed in batch system to evaluate kinetics and equilibrium of phenol adsorption. Adsorbent regeneration method was proposed to evaluate the reutilization of MAC in successive cycles of adsorption–desorption. Results showed that obtained magnetic compounds present cubic phase structure covered in activated carbon surface. MAC has microporous structure with functional groups like carbonyl and hydroxyl that can behave as adsorption sites. Kinetic studies indicate that adsorption rate increased rapidly around the initial 60 min, reaching equilibrium at 240 min; following pseudo-first-order and pseudo-second-order kinetic models in characterization concentrations of 50 and 100 mg L⁻¹, only the second-order model fit the kinetic data at 150 mg L⁻¹, while both models were outside the chi-square interval at 200 and 230 mg L⁻¹. The adsorption equilibrium is represented by Langmuir isotherm with high adsorption capacity of 116.0 ± 3.61 mg g⁻¹. The desorption experiments revealed that adsorption capacities of MAC still viable after three adsorption–desorption cycles. It was observed that chemical affinity of small concentrations of methanol with phenol allowed to exert greater desorption capacity to other solvents with permanence of adsorbed phenol of 17.5 mg g⁻¹.

中文翻译：

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苯酚在磁性活性炭上的吸附能力评估

在这项工作中，提出了一种以农工业废料椰子内果皮（Cocos nucifera L.）为原料合成磁性吸附剂以去除苯酚的替代利用方法。合成的吸附剂，命名为磁性活性炭（MAC），是通过共沉淀铁酸钴（CoFe ₂ O ₄) 到通过椰子内果皮碳化获得的活性炭表面上。MAC 的表征通过零电荷点 (PZC)、Brunauer、Emmett 和 Teller (BET) 表面积、扫描电子显微镜 (SEM)、X 射线荧光 (XRF)、傅里叶变换红外光谱 (FTIR)、 X射线衍射（XRD）分析和磁化曲线。在批处理系统中进行吸附实验以评估苯酚吸附的动力学和平衡。提出了吸附剂再生方法来评估 MAC 在连续吸附-解吸循环中的再利用。结果表明，所得磁性化合物呈立方相结构，覆盖在活性炭表面。MAC 具有微孔结构，具有可充当吸附位点的官能团，如羰基和羟基。动力学研究表明吸附速率在最初的 60 分钟左右迅速增加，在 240 分钟达到平衡；在 50 和 100 mg·L 的表征浓度下遵循伪一级和伪二级动力学模型^-1，只有二阶模型适合 150 mg L ^{-1的动力学数据，而两个模型均在 200 和 230 mg L -1}的卡方区间之外。吸附平衡由具有 116.0 ± 3.61 mg g ^-1的高吸附容量的 Langmuir 等温线表示。解吸实验表明 MAC 的吸附能力在三个吸附-解吸循环后仍然可行。据观察，小浓度甲醇与苯酚的化学亲和力允许对其他溶剂发挥更大的解吸能力，吸附苯酚的持久性为 17.5 mg g ^-1。