Adsorption performance of activated carbon synthesis by ZnCl2, KOH, H3PO4 with different activation temperatures from mixed fruit seeds

In this study, new activated carbons (ACs) were synthesized from a mixture of lemon and orange seeds (LOS) for toxic metal removal from aqueous solutions. Adsorbents have been produced by chemical activation with different activation agents (with H3PO4, ZnCl2 and KOH) and activation temperature (600°C, 700°C, 800°C). The elemental analysis, FT-IR, XRD and SEM analyses were performed to determine the characterization of the ACs. A series of batch adsorption experiments were done to research the influence of various parameters such as pH, adsorbent dosage, contact time, temperature, the complexing agents on the toxic metal ions (Cu(II), Cr(III) and Ni(II)) removal capacity of ACs. Adsorption equilibration time was 60 min, the adsorption capacity was 118.02 mg/g for Ni(II) ions, 146.03 mg/g for Cr(III) ions and 150.45 mg/g for Cu(II) ions. The adsorption of toxic metal ions was observed as a maximum at pH = 5 on AC-ZnCl2 (600°C) produced under N2 atmosphere. The adsorption process was fitted with a Langmuir isotherm model and a pseudo-second-order kinetic equation, showing the metal ions adsorption on AC was monolayer coverage. Thermodynamic studies show that the adsorption is endothermic and spontaneous in nature. AC produced from the LOS mixture has not been encountered in the literature. A simple, easy-to-apply method has been developed for a new adsorbent prepared from a mixture of LOS with environmentally friendly, easy to produce, reusable, cost-effective, non-toxic and with good adsorption-desorption capacity. Therefore, this study will contribute to the world economy in terms of environmental and wastewater cleaning.本研究以柠檬籽与橙籽混合物（Lemon and Orange Seeds, LOS）为原料，合成了新型活性炭（Activated Carbons, ACs），用于脱除水溶液中的有毒金属离子。通过采用不同活化剂（磷酸H₃PO₄、氯化锌ZnCl₂及氢氧化钾KOH）与活化温度（600℃、700℃、800℃）进行化学活化，成功制备得到该类吸附剂。采用元素分析、傅里叶变换红外光谱（Fourier Transform Infrared Spectroscopy, FT-IR）、X射线衍射（X-ray Diffraction, XRD）及扫描电子显微镜（Scanning Electron Microscope, SEM）对所制活性炭的物化性质进行表征。开展一系列间歇吸附实验，系统探究pH值、吸附剂投加量、接触时间、温度及络合剂等参数对活性炭去除Cu(II)、Cr(III)与Ni(II)等有毒金属离子吸附性能的影响。实验结果表明，吸附平衡时间为60 min，对Ni(II)、Cr(III)及Cu(II)的吸附容量分别可达118.02 mg/g、146.03 mg/g与150.45 mg/g。在氮气气氛下制备的AC-ZnCl₂（600℃）对有毒金属离子的吸附效果在pH=5时达到最优。该吸附过程符合朗缪尔（Langmuir）等温线模型与准二级动力学方程，表明活性炭对金属离子的吸附为单分子层覆盖过程。热力学研究结果显示，该吸附过程为吸热且自发进行的过程。目前尚无文献报道以LOS混合物为原料制备的活性炭。本研究开发了一种简便易行的制备方法，以LOS混合物为原料制备的新型吸附剂兼具环境友好、易于合成、可重复使用、成本低廉、无毒无害及优异的吸附-脱附性能。综上，本研究在环境治理与废水净化领域可为全球经济发展作出贡献。