Modified geosynthetic clay liners bentonite for barriers of Cr (VI) in contaminated soil

ABSTRACT

Hydroxy-Fe–Al and cetyltrimethylammonium bromide (CTMAB) were chosen to modified Na-bentonite (Na-bent). The characteristics of Na-bent and modified bentonites were determined with scanning electron microscopy (SEM), energy disperse spectroscopy (EDS), X-ray diffraction (XRD), Fourier transform infrared spectrum (FTIR) and zeta potential. It was found that CTMAB mainly entered the interlayer and hydroxy-Fe–Al groups were mostly loaded on the external surface of the Na-bent, respectively. The efficiency to remove Cr (VI) of Na-bent, organic modified bentonite (O-bent), inorganic modified bentonite (I-bent) and composite modified bentonite (Co-bent) followed the order: Co-bent > I-bent > O-bent > Na-bent. Adsorption experiments were carried out by the batch contact method. The highest removal rate of Cr (VI) by Co-bent was found to be 96.2% at optimal pH = 4. The Cr (VI) uptake on Co-bent from 50 mg/L solution rapidly attained equilibrium within 10 min, and the pesudo-second-order kinetic model could provide satisfactory fitting of the kinetic data (R² = 0.999) compared to the intraparticle diffusion model (R² = 0.585). The adsorption data were applied to the Langmuir, Freundlich, Temkin isotherm model. The Langmuir was found to be the most suitable equation to fit the experimental data (R² = 0.956) with a high Cr (VI) adsorption capacity of 27.472 mg/g, and R_L values (0.012–0.035) also indicated the adsorption could be accepted. The present study confirmed that Co-bent would be one of candidates for Cr (VI) adsorbent.

GRAPHICAL ABSTRACT

KEYWORDS:

• Composite modified bentonite
• hexavalent chromium
• adsorption capacity
• SEM-EDS
• adsorption mechanism

Acknowledgements

The authors gratefully acknowledge the financial support given by the Hunan Huxiang High-level talent gathering Project-Innovation team [grant number 2019RS1030]; National Natural Science Foundation of China [grant number 41807261; grant number 52078207].

Data availability statement

The data that support the findings of this study are available from the corresponding author, [Yang, W.], upon reasonable request.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The authors gratefully acknowledge the financial support given by the Hunan Huxiang High-level talent gathering Project-Innovation team [grant number 2019RS1030]; National Natural Science Foundation of China [grant number 41807261], [grant number 52078207].