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A composite material (CBC-nZVI) was synthesized by green reduction of Artemisia arenaria extract to produce nanoscale zero-valent iron (nZVI), which was subsequently loaded onto biochar derived from waste corn straw. This composite was employed for the removal of hexavalent chromium (Cr(Ⅵ)) from aqueous solutions. The study investigated the adsorption kinetics and thermodynamics, as well as the effects of pH, dosage, and coexisting ions on Cr(Ⅵ) removal by CBC-nZVI. The material was characterized using SEM, FTIR, XRD, and XPS to elucidate the Cr(Ⅵ) removal mechanisms. The adsorption kinetics of Cr(Ⅵ) onto CBC-nZVI fit best with the Elovich model, indicating that intraparticle diffusion was the rate-controlling step. The adsorption isotherm fitted the Freundlich model, indicating that the adsorption was a spontaneous endothermic and entropy-increasing process. The Cr(Ⅵ) removal efficiency improved with increasing reaction temperature, material dosage, and solution acidity. Under optimal conditions (298K, pH 2, and dosage of 1.0g/L), 100% removal efficiency was achieved for a Cr(Ⅵ) concentration of 30mg/L. The presence of coexisting cations or anions in the solution inhibited the removal of Cr(Ⅵ) by the CBC-nZVI to varying degrees, with the order of inhibition being Cd2+>Mg2+>Ca2+>Cu2-, and CO32->Cl->NO3->SO42-. The results of characterization of CBC-nZVI and batch adsorption experiments showed that the Cr(Ⅵ) removal mechanism by CBC-nZVI involves electrostatic adsorption, chemical reduction, functional group complexation, and precipitation. nZVI reduces adsorbed Cr(Ⅵ) to Cr(Ⅲ), which is then removed through surface complexation with functional groups and co-precipitation with Fe(Ⅲ) as Cr(Ⅲ)-Fe(Ⅲ) complexes. The loaded nZVI and CBC exhibited a synergistic effect in the removal of Cr(Ⅵ) by the composite material.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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