Efficient Removal of Hexavalent Chromium from an Aquatic System Using Nanoscale Zero-Valent Iron Supported by Ramie Biochar

Abstract

In this study, ramie biochar (RBC) was used to activate nano zero-valent iron (nZVI) to enhance hexavalent chromium (Cr(VI)) removal. The best results were obtained at a pyrolysis temperature of 600 °C, a biochar particle size of < 150 μm, and an iron to carbon ratio = 1:1. Under the optimal conditions, the removal of Cr(VI) by RBC600-nZVI (98.69%) was much greater than that of RBC600 (12.42%) and nZVI (58.26%). Scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS) revealed that the reaction mechanism at the Fe and Cr interface was a multiple interaction mechanism with reduction dominated, adsorption, and co-precipitation simultaneously. The enhanced performance of RBC600-nZVI resulted from the effective dispersion of nZVI on the surface of RBC600, therefore increasing the adsorption activity sites. At the same time, RBC600 and nZVI exerted a synergistic influence on the composite structure, which jointly promoted the reduction reaction of Cr(VI) and removed more Cr(VI). This study shows that RBC-nZVI is a potentially valuable remediation material that not only provides a new idea for the utilization of ramie waste, but also effectively overcomes the limitations of nZVI, thus, achieving efficient and rapid remediation of Cr(VI).

Enhanced Adsorptivity of Hexavalent Chromium in Aqueous Solutions Using CTS@nZVI Modified Wheat Straw-Derived Porous Carbon

“…nZVI-WSPC [ 24 , 25 ]: 2 g of wheat straw biochar (WSPC) was dispersed in 50 mL of FeSO 4 ·7H 2 O solution with a concentration of 0.1 mol/L and stirred for 2 h. After that, 50 mL of aqueous ethanol solution with a volume ratio of 1:1 was added as a dispersant to a three-port reaction glass flask, followed by 50 mL of NaBH 4 solution at a concentration of 0.25 mol/L at a rate of 2 drops/s under nitrogen. Approximately 30 min later, biochar-loaded nanoscale zero-valent iron particles were successfully synthesized.…”

Environmental remediation approaches by nanoscale zero valent iron (nZVI) based on its reductivity: a review

“…Converting highly toxic Cr( vi ) to low-toxic and separable immobilized Cr( iii ) by nZVI via adsorption–reduction–precipitation has garnered increasing research attention. As there are various limitations of pristine nZVI during production and application, including easy agglomeration, fast oxidation, and easy deactivation, 61,106 nZVI is commonly loaded in porous materials, such as bentonite, 107 attapulgite, 108 SBA-15, 109 graphene, 110 biochar, 111–116 resin, 117 hydrogel, 118–120 membrane, 121,122 MOF 106 etc. The supporting not only prevents aggregation and deactivation of nZVI, but also endows nZVI materials with high and/or selective adsorption towards Cr( vi ).…”

Chromium(VI) Removal from Water by Lanthanum Hybrid Modified Activated Carbon Produced from Coconut Shells

“…On the other hand, adsorption has several advantages compared to other techniques, more importantly that is being cost effective and more efficient in removal of heavy metals from water, especially for treatment of waters with concentrations slightly higher than the legislative limits. Several adsorbents have been studied for the removal of Cr(VI) from waters [ 23 ], such as nickel oxide nanoparticles [ 24 ], chitosan grafted [ 25 ] and polypyrrole [ 26 ] graphene oxide nanocomposites, biochar [ 27 ] etc. In particular, adsorbents based on activated carbon are very promising in terms of performance [ 28 ], surface area, adsorption capacity and fast reaction rate [ 29 ].…”