Sustainable Chromium (VI) Removal from Contaminated Groundwater Using Nano-Magnetite-Modified Biochar via Rapid Microwave Synthesis

Abstract

This study developed a nano-magnetite-modified biochar material (m-biochar) using a simple and rapid in situ synthesis method via microwave treatment, and systematically investigated the removal capability and mechanism of chromium (VI) by this m-biochar from contaminated groundwater. The m-biochar was fabricated from reed residues and magnetically modified by nano-Fe3O4. The results from scanning electron microscopy (SEM) and X-ray diffraction (XRD) characterisations confirmed the successful doping of nano-Fe3O4 on the biochar with an improved porous structure. The synthesised m-biochar exhibited significantly higher maximum adsorption capacity of 9.92 mg/g compared with that (8.03 mg/g) of the pristine biochar. The adsorption kinetics followed the pseudo-second-order model and the intraparticle diffusion model, which indicated that the overall adsorption rate of Cr(VI) was governed by the processes of chemical adsorption, liquid film diffusion and intramolecular diffusion. The increasing of the pH from 3 to 11 significantly affected the Cr(VI) adsorption, where the capabilities decreased from 9.92 mg/g to 0.435 mg/g and 8.03 mg/g to 0.095 mg/g for the m-biochar and pristine biochar, respectively. Moreover, the adsorption mechanisms of Cr(VI) by m-biochar were evaluated and confirmed to include the pathways of electrostatic adsorption, reduction and complexation. This study highlighted an effective synthesis method to prepare a superior Cr(VI) adsorbent, which could contribute to the effective remediation of heavy metal contaminations in the groundwater.

Removal of Methylene Blue from Water Using Magnetic GTL-Derived Biosolids: Study of Adsorption Isotherms and Kinetic Models

“…The XRD analysis of KBS shows the prominent presence of magnetite and potassium iron oxide (K 2 Fe 4 O 7 , KFeO 2 ), while calcite was seen to be the only ‘major’ deposit detected on the pristine sample ( Figure 3 ). The diffraction peaks at 35.2° matched well with the PDF spectrum of Fe 3 O 4, showing the presence of magnetic properties after activation [ 26 ]. Further analysis of KBS using a tesla meter revealed a magnetic field of 0.1 mT, confirming the sample is weakly magnetic.…”

Synthesis of Fe3O4/Fe2O3 nanoparticles modified with peroxidase with incorporated chromium and manganese ions

“…41,42 Intramolecular diffusion processes have a decisive impact on the rate if the adsorbent concentration is high and the affinity of the adsorbate for the adsorbent is low, which is the case in the studies described here. 43 The thermodynamics of the process was investigated based on the thermodynamic equilibrium coefficients obtained from the dependence of the variation of the component concentration in the temperature range of 25-45 1C. The adsorption characteristics of the material were determined using thermodynamic parameters such as DG 0 ads , DH 0 , and DS 0 (Table 6).…”

Mitigating the Health Effects of Aqueous Cr(VI) with Iron-Modified Biochar

“…The maximum adsorption capacity of the MHDB was about 13.70 mg/g at 35 • C, which was higher than those of multiple other types of biochars from previous studies. For instance, the adsorption capacities of Cr(VI) by the pineapple peel-derived biochar, the natural zeolite-derived biochar, the nano-magnetite-modified biochar material, and the cornstalk-derived biochar were 7.44 mg/g, 6.08 mg/g, 9.92 mg/g, and 9.25 mg/g, respectively [61][62][63][64]. Thus, the modified honeysuckle-derived biochar is a promising adsorbent for Cr(VI) removal and could be a valuable reference for the resource recovery of TCMRs, alleviating the environmental pollution problem from the chromium-containing wastewater.…”