Green synthesis of CaO-Fe₃O₄ composites for photocatalytic degradation and adsorption of synthetic dyes

IF 5.8 3区 环境科学与生态学 0 ENVIRONMENTAL SCIENCES
Odín Reyes-Vallejo, Rocío Magdalena Sánchez-Albores, José Escorcia-García, Abumale Cruz-Salomón, Pascual Bartolo-Pérez, Ashok Adhikari, Maritza del Carmen Hernández-Cruz, Héctor Hiram Torres-Ventura, Héctor Armando Esquinca-Avilés
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Abstract

The efficient removal of synthetic dyes, such as methylene blue (MB) and malachite green (MG), continues to pose a significant challenge due to their high stability, toxicity, and resistance to conventional treatment methods. In this study, CaO-Fe₃O₄ compounds were synthesized using a sustainable ball-milling technique, utilizing calcium oxide derived from eggshells and Fe₃O₄. The compounds were calcined at temperatures ranging from 200 to 800 °C to optimize their structural and photocatalytic properties. The sample calcined at 400 °C exhibited the highest surface area (17.86 m2/g), the narrowest bandgap (2.10 eV), and the coexistence of CaO, Ca(OH)₂, and γ-Fe₂O₃ phases, making it an ideal candidate for achieving high dye removal efficiency. Under visible light, this sample completely degraded MB at 10 ppm within 30 min, following pseudo-first-order kinetics with a rate constant (kₐₚₚ) of 0.110 min−1 and a half-life (t/₂) of 6.30 min. At an MB concentration of 50 ppm, complete degradation was achieved in 90 min. Radical scavenging experiments indicated that superoxide radicals (·O₂) played a key role in the degradation mechanism. For MG (100 ppm), the maximum adsorption capacity (qₑ) was 1111.11 mg/g, fitting the Langmuir model (R2 = 0.996) with an equilibrium constant (KL) of 0.6822 L/mg, indicating a highly favorable process. The adsorption kinetics followed a pseudo-second-order model (R2 ≈ 0.999), suggesting chemisorption as the rate-limiting step. Thermodynamic parameters confirmed that MG adsorption was spontaneous and endothermic, with negative Gibbs free energy, positive enthalpy, and increased entropy. This study proposes an eco-friendly and efficient approach for dye removal, integrating waste valorization.

Graphical Abstract

绿色合成CaO-Fe₃O₄复合材料,用于光催化降解和吸附合成染料。
合成染料,如亚甲基蓝(MB)和孔雀石绿(MG),由于其高稳定性、毒性和对传统处理方法的抗性,仍然是一个重大挑战。在这项研究中,以蛋壳为原料的氧化钙和Fe₃O₄为原料,采用可持续球磨技术合成了CaO-Fe₃O₄化合物。这些化合物在200 ~ 800℃的温度下煅烧,以优化其结构和光催化性能。在400°C下煅烧的样品具有最高的比表面积(17.86 m2/g),最窄的带隙(2.10 eV),并且存在CaO、Ca(OH)₂和γ-Fe₂O₃相,是实现高脱染效率的理想候选物。在可见光下,该样品在10 ppm下在30 min内完全降解MB,遵循准一级动力学,速率常数(kₚₚ)为0.110 min-1,半衰期(t₁/ 2)为6.30 min。在50 ppm的MB浓度下,在90 min内完全降解。自由基清除实验表明,超氧自由基(·O₂-)在降解机制中起关键作用。对于MG (100 ppm),最大吸附量(qₑ)为1111.11 MG /g,符合Langmuir模型(R2 = 0.996),平衡常数(KL)为0.6822 L/ MG,表明该过程非常有利。吸附动力学服从拟二阶模型(R2≈0.999),表明化学吸附是其限速步骤。热力学参数证实MG吸附为自发吸热吸附,吉布斯自由能为负,焓为正,熵增大。本研究提出了一种环保、高效的染料去除方法,结合废物增值。
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来源期刊
CiteScore
8.70
自引率
17.20%
发文量
6549
审稿时长
3.8 months
期刊介绍: Environmental Science and Pollution Research (ESPR) serves the international community in all areas of Environmental Science and related subjects with emphasis on chemical compounds. This includes: - Terrestrial Biology and Ecology - Aquatic Biology and Ecology - Atmospheric Chemistry - Environmental Microbiology/Biobased Energy Sources - Phytoremediation and Ecosystem Restoration - Environmental Analyses and Monitoring - Assessment of Risks and Interactions of Pollutants in the Environment - Conservation Biology and Sustainable Agriculture - Impact of Chemicals/Pollutants on Human and Animal Health It reports from a broad interdisciplinary outlook.
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