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. 2024 Jul 15;14(31):22266-22279.
doi: 10.1039/d4ra03479a. eCollection 2024 Jul 12.

Engineering a sustainable cadmium sulfide/polyethyleneimine-functionalized biochar/chitosan composite for effective chromium adsorption: optimization, co-interfering anions, and mechanisms

Abdelazeem S Eltaweil  1   2 , Nouf Al Harby  3 , Mervette El Batouti  2 , Eman M Abd El-Monaem  2
Affiliations

Engineering a sustainable cadmium sulfide/polyethyleneimine-functionalized biochar/chitosan composite for effective chromium adsorption: optimization, co-interfering anions, and mechanisms

Abdelazeem S Eltaweil et al. RSC Adv. .

Abstract

A novel eco-friendly adsorbent was fabricated by mixing mushroom-derived cadmium sulfide and polyethyleneimine-functionalized biochar that was fabricated from coffee waste with a chitosan biopolymer. The green-synthesized CdS/PEI-BC/CTS composite was analyzed using several characterization methods to identify its morphological, compositional, and structural characteristics. In addition, the adsorption property of the composite was investigated for hexavalent chromium as a model for anionic heavy metals. The best adsorption conditions to efficiently adsorb Cr(vi) onto CdS/PEI-BC/CTS were scrutinized in the batch mode. The experimental results elucidated that the higher adsorption efficacy for Cr(vi) was 97.89% at pH = 3, Cr(vi) concentration = 50 mg L-1, CdS/PEI-BC/CTS dose = 0.01 g, and temperature = 20 °C. The impact of co-interfering anionic species on Cr(vi) adsorption was identified in simulated wastewater. The recycling property of the CdS/PEI-BC/CTS composite was assessed for ten runs to ensure the applicability of the green composite. The adsorption mechanism and interaction types were proposed on the basis of kinetic and isotherm studies, along with analysis tools. The mechanistic study proposed that the Cr(vi) adsorption onto CdS/PEI-BC/CTS occurred via chemical and physical pathways, including protonation, electrostatic interactions, reduction, and coordination bonds.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Fig. 1
Fig. 1. (A) FTIR and (B) XRD of CTS, CdS, BC, PEI-BC, and CdS/PEI-BC/CTS. (C) Zeta potential of CdS/PEI-BC/CTS.
Fig. 2
Fig. 2. SEM images of (A) CTS, (B) CdS, (C) BC, (D) PEI-BC, and (E) CdS/PEI-BC/CTS composite.
Fig. 3
Fig. 3. The XPS spectra of the CdS/PEI-BC/CTS composite: (A) survey, (B) Cd 3d, (C) O 1s, (D) C 1s, (E) S 2p, and (F) N 1s.
Fig. 4
Fig. 4. Optimization of the Cr(vi) adsorption process: (A) comparison test, (B) identifying the optimal pH, (C) identifying the impact of the adsorbent dose, (D) identifying the thermodynamic behavior of the Cr(vi) adsorption process, and (E, F) identifying the influence of the initial Cr(vi) concentrations.
Fig. 5
Fig. 5. (A) Effect of co-interfering ions, (B) recycling test of CdS/PEI-BC/CTS, and (C) XRD patterns of CdS/PEI-BC/CTS before and after the Cr(vi) adsorption process.
Fig. 6
Fig. 6. (A) Isotherm study and (B) kinetic study for Cr(vi) adsorption onto the CdS/PEI-BC/CTS composite.
Fig. 7
Fig. 7. The XPS spectra of the Cr(vi)-adsorbed CdS/PEI-BC/CTS composite: (A) survey, (B) N 1s, (C) Cr 2p, (D) O 1s, and (E) Cd 3d.
Fig. 8
Fig. 8. Possible interactions between Cr(vi) and the CdS/PEI-BC/CTS composite.
See this image and copyright information in PMC

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