Adsorption of hexavalent chromium from wastewater using magnetic biochar derived from peanut hulls

IF 3 3区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Physics and Chemistry of the Earth Pub Date : 2024-11-16 DOI:10.1016/j.pce.2024.103815

Lehlogonolo Tabana, Annita Kupa, Shepherd Tichapondwa

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Abstract

In this study, the utilization of peanut hulls as a precursor for the preparation of magnetic biochar through pyrolysis was investigated. To enhance the magnetic and adsorption properties of the biochar, the peanut hulls biomass was modified using ferric chloride hexahydrate and magnesium chloride hexahydrate. Response surface methodology was employed to evaluate the influence of biomass metal concentration, pyrolysis temperature, pyrolysis period and flow of nitrogen on the yield and Cr (VI) adsorption efficiency of the synthesized biochar. A 17-run experimental matrix was generated using Optimal Design to investigate the interactions among four input parameters. The results led to the development of a quadratic model, which demonstrated a high degree of predictability in accordance with the experimental data. Analysis of variance (ANOVA) confirmed that the models for yield and Cr (VI) adsorption efficiency were highly significant (p < 0.05), with coefficients of determination (R²) values of 0.891 and 0.988, respectively. The optimal synthesis conditions for producing biochar with superior physicochemical properties were identified as a pyrolysis temperature of 300 °C, a pyrolysis duration of 2 h, a metal-to-biomass ratio of 0.5, and a constant flow of nitrogen. A desirability of 85% was achieved through numerical optimization, corresponding to a yield of 63% and complete Cr (VI) removal. Further optimization of Cr (VI) adsorption efficiency, considering the effects of pH (3–12), adsorbent loading (1–15 g/L), and initial Cr (VI) concentration (5–20 mg/L), was performed using a 19-run experimental matrix. ANOVA for Cr (VI) adsorption efficiency model revealed high significance (p < 0.05) with an R² value of 0.916.

The magnetic biochar demonstrated a remarkable adsorption efficiency of 98% under the experimental conditions of solution pH 3, adsorbent dosage of 5 g/L, and an initial Cr (VI) concentration of 20 mg/L. The desirability of 100% was obtained by a numerical optimization method representing Cr (VI) removal of 98%. The adsorption behaviour was adequately described by the Freundlich isotherm model, suggesting multilayer adsorption, with a maximum adsorption capacity of 12 mg/g. Biochar also proved to have strong magnetic properties which enhanced solid-liquid separation post adsorption experiments.

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利用花生壳提取的磁性生物炭吸附废水中的六价铬

本研究探讨了如何利用花生壳作为前体，通过热解制备磁性生物炭。为了增强生物炭的磁性和吸附性，使用六水氯化铁和六水氯化镁对花生壳生物质进行了改性。采用响应面方法评估了生物质金属浓度、热解温度、热解周期和氮气流量对合成生物炭产量和六（Cr）吸附效率的影响。利用优化设计生成了一个 17 次运行的实验矩阵，以研究四个输入参数之间的相互作用。结果建立了一个二次方模型，该模型与实验数据相符，具有很高的可预测性。方差分析（ANOVA）证实，产量和 Cr (VI) 吸附效率模型非常显著（p < 0.05），决定系数（R2）分别为 0.891 和 0.988。为生产具有优异物理化学特性的生物炭，确定了最佳合成条件：热解温度为 300 °C，热解持续时间为 2 小时，金属与生物质比率为 0.5，氮气流量恒定。通过数值优化，达到了 85% 的理想值，相当于 63% 的产率和完全去除 Cr (VI)。考虑到 pH 值（3-12）、吸附剂负载量（1-15 克/升）和初始六价铬浓度（5-20 毫克/升）的影响，使用 19 次实验矩阵对六价铬吸附效率进行了进一步优化。在溶液 pH 值为 3、吸附剂用量为 5 g/L、初始 Cr (VI) 浓度为 20 mg/L 的实验条件下，磁性生物炭的吸附效率高达 98%。通过数值优化方法获得了 100%的理想值，代表铬（VI）的去除率为 98%。吸附行为由 Freundlich 等温线模型充分描述，表明存在多层吸附，最大吸附容量为 12 毫克/克。生物炭还被证明具有很强的磁性，这增强了吸附实验后的固液分离效果。

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来源期刊

Physics and Chemistry of the Earth 地学-地球科学综合

CiteScore

5.40

自引率

2.70%

发文量

176

审稿时长

31.6 weeks

期刊介绍： Physics and Chemistry of the Earth is an international interdisciplinary journal for the rapid publication of collections of refereed communications in separate thematic issues, either stemming from scientific meetings, or, especially compiled for the occasion. There is no restriction on the length of articles published in the journal. Physics and Chemistry of the Earth incorporates the separate Parts A, B and C which existed until the end of 2001. Please note: the Editors are unable to consider submissions that are not invited or linked to a thematic issue. Please do not submit unsolicited papers. The journal covers the following subject areas: -Solid Earth and Geodesy: (geology, geochemistry, tectonophysics, seismology, volcanology, palaeomagnetism and rock magnetism, electromagnetism and potential fields, marine and environmental geosciences as well as geodesy). -Hydrology, Oceans and Atmosphere: (hydrology and water resources research, engineering and management, oceanography and oceanic chemistry, shelf, sea, lake and river sciences, meteorology and atmospheric sciences incl. chemistry as well as climatology and glaciology). -Solar-Terrestrial and Planetary Science: (solar, heliospheric and solar-planetary sciences, geology, geophysics and atmospheric sciences of planets, satellites and small bodies as well as cosmochemistry and exobiology).