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. 2025 Aug 26;15(37):30123-30134.
doi: 10.1039/d5ra03405a. eCollection 2025 Aug 22.

Synthesis of biochar/MoS2 composite modified with poly(acrylic acid) (BC/MoS2/PAA) for the removal of Cd(ii) and Pb(ii) from wastewater

Salami Hammed Olawale  1   2 , Waleed Alahmad  1 , Ibrahim A Darwish  3 , Mohammad Ashfaq  4 , Ryhan J Darling  5 , Charoenkwan Kraiya  1   2
Affiliations

Synthesis of biochar/MoS2 composite modified with poly(acrylic acid) (BC/MoS2/PAA) for the removal of Cd(ii) and Pb(ii) from wastewater

Salami Hammed Olawale et al. RSC Adv. .

Abstract

The present study focuses on the synthesis of coconut shell-derived biochar (BC), molybdenum disulfide (MoS2), and poly(acrylic acid) (PAA) (BC/MoS2/PAA) composite. The composite was synthesized via a simple hydrothermal method. The structural and morphological features of the resulting composite were thoroughly characterized using Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS), Brunauer-Emmett-Teller (BET) surface analysis, and Raman spectroscopy. These analyses confirmed the successful formation and integration of the composite components. Adsorption isotherm studies revealed that Cd(ii) and Pb(ii) ions uptake by the BC/MoS2/PAA composite adhered to the Langmuir model, indicating monolayer adsorption onto a homogeneous surface. The maximum adsorption capacities for Cd(ii) and Pb(ii) were determined to be 8.23 mg g-1 and 26.47 mg g-1, respectively. Kinetic investigations indicated that the adsorption process followed a pseudo-second-order model, suggesting that chemisorption was the dominant mechanism. Moreover, the composite exhibited excellent reusability and selectivity towards Cd(ii) and Pb(ii) ions. Oxygen-containing functional groups, sulfide ions (S2-), and π-π interactions within the composite imply that electrostatic attraction, surface complexation, and cation-π interactions were the primary forces governing the adsorption process. These findings highlight the BC/MoS2/PAA composite's significant potential for effectively removing Cd(ii) and Pb(ii) from contaminated wastewater.

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Conflict of interest statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Figures

Fig. 1
Fig. 1. Point of zero charge (pHpzc) of BC/MoS2/PAA adsorbent.
Fig. 2
Fig. 2. SEM image of (a and b) BC, (c and d) BC/MoS2, and (e and f) BC/MoS2/PAA. EDS analysis of (g) BC, (h) BC/MoS2, and (i) BC/MoS2/PAA composite.
Fig. 3
Fig. 3. (a) XRD, (b) FTIR, and (c) Raman spectra of the BC, BC/MoS2, and BC/MoS2/PAA composite.
Fig. 4
Fig. 4. Linearized N2 adsorption–desorption isotherms and pore size distributions for the (a) BC/MoS2 and (b) BC/MoS2/PAA composite.
Fig. 5
Fig. 5. Comparison of percentage removal of Pb(ii) and Cd(ii) on adsorbent material (experimental conditions: concentration = 10 mg L−1; dose = 0.010 g/10 mL; time = 720 min).
Fig. 6
Fig. 6. (a) Effect of adsorbent dosage; (b) effects of solution pH; (c) effects of contact time.
Fig. 7
Fig. 7. Linear plots of adsorption kinetics of Cd(ii) and Pb(ii) on BC/MoS2/PAA. (a) Pseudo-second order (b) pseudo-second order (c) intraparticle diffusion model (condition: concentration = 10 mg L−1; pH 6 for Pb(ii); time = 30 min; dosage = 0.010 gram and pH 7 for Cd(ii); adsorbent dosage = 0.025 gram).
Fig. 8
Fig. 8. Effects of initial concentration on the adsorption of (a) Pb(ii) and Cd(ii) onto BC/MoS2/PAA (condition: pH 6 for Pb(ii); adsorbent dosage = 0.010 g; time = 30 min for Pb(ii) and pH 7 for Cd(ii); adsorbent dosage = 0.025 g; time = 30 min).
Fig. 9
Fig. 9. Adsorption isotherm model analysis. Linear plot for (a) Langmuir isotherm model (b) Freundlich isotherm model (c) Temkin isotherm model for Cd(ii) and Pb(ii) adsorption on BC/MoS2/PAA composite (condition: pH 6 for Pb(ii); dosage = 0.010 g; time = 30 min for Pb(ii) and pH 7 for Cd(ii); dosage = 0.025 g; time = 30 min).
Fig. 10
Fig. 10. (a) Influence of co-existing ions on Pb(ii) and Cd(ii) adsorption using BC/MoS2/PAA composite (b) regeneration test of BC/MoS2/PAA composite towards Pb(ii) and Cd(ii) after five regeneration cycles.
Fig. 11
Fig. 11. (a) FTIR spectra of before and after adsorption of Pb(ii) and Cd(ii) (b) possible sorption mechanism on BC/MoS2/PAA composite for Pb(ii) and Cd(ii).
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