Biochar is a promising material for removing metal ions from water and soil through adsorption. In this study, rice straw was pyrolyzed to prepare biochars at 300 °C (RSBC300), 500 °C (RSBC500), and 700 °C (RSBC700) in an oxygen-limited atmosphere. The biochars were used in batch experiments for adsorption of copper (Cu) ions in aqueous solution. The influence of various environmental conditions, including solution pH, solid-to-liquid ratio, contact time, and environmental temperature, on Cu removal were systematically investigated. To explore the adsorption mechanisms and ascertain the contribution of acid-soluble minerals, adsorption kinetics and isotherm analyses, Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) were performed. The results showed that the removal rate reached 99.6% when the experimental condition was a solid-to-liquid ratio of 1 g L⁻¹, pH of 6.0, and the initial Cu concentration of 30 mg L⁻¹. The pseudo-second-order model and the two-compartment kinetic model well fitted with the Cu adsorption kinetics process onto RSBC700, whereas the Freundlich, Temkin, and Dubinin–Radushkevich (D–R) models best described the Cu adsorption isotherm process on RSBC700. Higher temperatures improved Cu removal from solution with the maximum adsorption capacity being 52.5 mg g⁻¹ at 45 °C. The influence of co-existing Ca²⁺ and Mg²⁺ on Cu removal by RSBC700 was limited, whereas tetracycline exhibited some inhibition effect. The role of acid-soluble minerals in biochar for Cu removal cannot be ignored, especially in treatment using RSBC500 (contribution rate at 47.2–57.1%). The mechanism underlying Cu removal by rice straw biochar involved electrostatic interaction, complexation, cation–π interaction, and precipitation. Therefore, high temperature-derived rice straw biochar can be expected to an adsorbent to alleviate Cu pollution in wastewater.

中文翻译：

---

稻草中用于去除水溶液中Cu 2+的生物炭：酸溶性矿物的作用机理与贡献

生物炭是一种通过吸附去除水和土壤中金属离子的有前途的材料。在这项研究中，将稻草热解在氧气受限的环境中分别于300°C（RSBC300），500°C（RSBC500）和700°C（RSBC700）制备生物炭。生物炭用于批量实验中，以吸附水溶液中的铜（Cu）离子。系统地研究了溶液pH值，固液比，接触时间和环境温度等各种环境条件对铜去除的影响。为了探索吸附机理并确定酸溶性矿物的贡献，吸附动力学和等温分析，进行了傅里叶变换红外光谱（FTIR）和X射线光电子能谱（XPS）。结果表明，去除率达到99。^-1，pH 6.0和初始Cu浓度30 mg L ^-1。伪二阶模型和两室动力学模型非常适合RSBC700上的Cu吸附动力学过程，而Freundlich，Temkin和Dubinin-Radushkevich（D-R）模型最能描述RSBC700上的Cu吸附等温过程。 。更高的温度改善了溶液中的铜去除率，在45°C下的最大吸附容量为52.5 mg g ^-1。Ca ²⁺和Mg ²⁺共存的影响RSBC700对铜的去除作用有限，而四环素具有一定的抑制作用。酸溶性矿物在生物炭去除Cu中的作用不容忽视，尤其是在使用RSBC500的处理中（贡献率为47.2-57.1％）。稻草生物炭去除铜的机理涉及静电相互作用，络合，阳离子-π相互作用和沉淀。因此，可以预期高温稻秆生物炭为吸附剂，以减轻废水中的铜污染。