Biochar from Rice Straw for Cu 2+ Removal from Aqueous Solutions: Mechanism and Contribution Made by Acid-Soluble Minera
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Biochar from Rice Straw for Cu2+ Removal from Aqueous Solutions: Mechanism and Contribution Made by Acid-Soluble Minerals Yanglu Mei & Bin Li & Shisuo Fan
Received: 24 April 2020 / Accepted: 23 July 2020 # Springer Nature Switzerland AG 2020
Abstract 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
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11270-020-04791-9) contains supplementary material, which is available to authorized users. Y. Mei : B. Li : S. Fan (*) School of Resources and Environment, Anhui Agricultural University, Hefei 230036, China e-mail: [email protected]
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. Keywords Rice straw . Biochar . Toxic metal . Model fitting . Acid-soluble minerals . Functional groups
1 Introduction The rapid development of industry and agriculture has resulted in the discharge of large amounts of wastewater or solid waste containing toxic metals into the environment, which has led to metal accumulation in water or soil. This poses a serious threat to ecological security and human health. Take copper (Cu) for example, although it is an essential element for the human body, plants, and animals, it can also deteriorate environment at hi
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