The powdered activated carbon (AC) supported by carbonaceous nano-adsorbents were examined to remove hexavalent chromium [Cr(VI)] from aqueous solution The adsorption behaviour of micro-level concentration of Cr(VI) on those nano-adsorbents was investigated as a function of the experimental conditions such as the contact time, the pH, the dosage of adsorbent, and the initial concentration of Cr(VI). The structural characterization of the adsorbents was accomplished by Fourier transform infrared spectroscopy and scanning electron microscopy. Adsorption isotherms including Freundlich and Langmuir have been applied to study the equilibrium of the adsorption behaviour and identify the adsorption capacity of the activated carbon-functionalized multiwalled carbon nanotubes (AC/f-MWCNTs) and activated carbon-functionalized carbon nanospheres (AC/f-CNSs). Langmuir isotherm model showed that the adsorption process was monolayer type under working with an adsorption capacity of 113.29 and 105.48 mg/g, respectively, for AC/f-MWCNTs and (AC/f-CNSs).
The green adsorbents were prepared by using cranberry (Cornus mas) kernel shell (CKS), rosehip (Rosa canina) seed shell (RSS), and banana (Musa cavendishii) peel (BP) and were proved in removing Cr(VI). Several parameters to remove Cr(VI) such as pH, adsorbent dosage, contact time, initial Cr(VI) ions concentration, and temperature were tested. The functional groups in the matrix of CKS, RSS, and BP were detected by FT-IR for raw biomasses together with Cr(VI). The equilibrium results were inspected using four different isotherm models, with a better fitting to the Langmuir model. The maximum adsorption quantities for Cr(VI) ions were 10.42, 15.17, and 6.81 mg/g for BP, RSS, and CKS, respectively. The interrelationship coefficients were expressed by a pseudo-second-order kinetic model, assuming that the overall Cr(VI) adsorption rate is limited by the rate of adsorbate diffusion in the pores of biomass.
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