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. 2023 Jul 17;8(30):26725-26738.
doi: 10.1021/acsomega.2c05765. eCollection 2023 Aug 1.

Synthesis and Characterization of MC/TiO2 NPs Nanocomposite for Removal of Pb2+ and Reuse of Spent Adsorbent for Blood Fingerprint Detection

Yvonne Boitumelo Nthwane  1 , Bienvenu Gael Fouda-Mbanga  2 , Melusi Thwala  3   4 , Kriveshini Pillay  1
Affiliations

Synthesis and Characterization of MC/TiO2 NPs Nanocomposite for Removal of Pb2+ and Reuse of Spent Adsorbent for Blood Fingerprint Detection

Yvonne Boitumelo Nthwane et al. ACS Omega. .

Abstract

The removal of toxic heavy metals from wastewater through the use of novel adsorbents is expensive. The challenge arises after the heavy metal is removed by the adsorbent, and the fate of the adsorbent is not taken care of. This may create secondary pollution. The study aimed to prepare mesoporous carbon (MC) from macadamia nutshells coated with titanium dioxide nanoparticles (TiO2 NPs) using a hydrothermal method to remove Pb2+ and to test the effectiveness of reusing the lead-loaded spent adsorbent (Pb2+-MC/TiO2 NP nanocomposite) in blood fingerprint detection. The samples were characterized using SEM, which confirmed spherical and flower-like structures of the nanomaterials, whereas TEM confirmed a particle size of 5 nm. The presence of functional groups such as C and Ti and a crystalline size of 4 nm were confirmed by FTIR and XRD, respectively. The surface area of 1283.822 m2/g for the MC/TiO2 NP nanocomposite was examined by BET. The removal of Pb2+ at pH 4 and the dosage of 1.6 g/L with the highest percentage removal of 98% were analyzed by ICP-OES. The Langmuir isotherm model best fit the experimental data, and the maximum adsorption capacity of the MC/TiO2 NP nanocomposite was 168.919 mg/g. The adsorption followed the pseudo-second-order kinetic model. The ΔH° (-54.783) represented the exothermic nature, and ΔG° (-0.133 to -4.743) indicated that the adsorption process is spontaneous. In the blood fingerprint detection, the fingerprint details were more visible after applying the Pb2+-MC/TiO2 NP nanocomposite than before the application. The reuse application experiments showed that the Pb2+-MC/TiO2 NP nanocomposite might be a useful alternative material for blood fingerprint enhancement when applied on nonporous surfaces, eliminating secondary pollution.

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Conflict of interest statement

The authors declare no competing financial interest.

Figures

Scheme 1
Scheme 1. Preparation of Carbon-Derived Macadamia Nutshells
Scheme 2
Scheme 2. Synthesis of Mesoporous Carbon-Coated TiO2NPs Nanocomposite
Figure 1
Figure 1
XRD patterns of (a) MC, (b) the MC/TiO2 NP nanocomposite, FTIR spectra of (c, i) MC and (ii) MC/TiO2 nanocomposite, (d) N2 adsorption–desorption isotherm curve of (i) MC and (ii) MC/TiO2 NP nanocomposite, (e) TGA curve of (i) MC/TiO2 NP nanocomposite (ii) MC.
Figure 2
Figure 2
SEM images of (a) MC, (b) TiO2 NPs, (c) the MC/TiO2 NP nanocomposite, and (d) the Pb2+-MC/TiO2 NP nanocomposite. EDX spectrum of (e) the MC/TiO2 NP nanocomposite and (f) the Pb2+-MC/TiO2 NP nanocomposite.
Figure 3
Figure 3
TEM images at different magnifications: (a, i) 100 nm to (ii) 50 nm MC, (b, i) 100 nm to (ii) 50 nm MC/TiO2 NP nanocomposite.
Figure 4
Figure 4
Plot of (a) the effect of pH (2–12, dosage of 2 g/L, Pb2+ ions of 20 ppm, T = 25 °C), (b) pHPZC, (c) effect of adsorbent dose (0.4–2.4 g/L, Pb2+ ion of 20 ppm, pH 4, T = 25 °C). (d) Distribution of species as a function of pH and equilibriums of Pb2+ ions in aqueous medium. The error bars represent the triplicate data’s standard deviation. Adapted or reprinted in part with permission from ref (76). Copyright 2019, Springer Publishers.
Figure 5
Figure 5
Fit of data to linear (a) Langmuir, (b) Freundlich, and (c) Temkin for Pb2+ adsorption by the MC/TiO2 NP nanocomposite. (d) A plot of concentration versus temperature (50 to 300 ppm, pH 4, dosage of 1.6 g/L, T = 25 to 55 °C), data fit to nonlinear (e) Langmuir and Freundlich.
Figure 6
Figure 6
Plot of linearized data of (A) pseudo-first-order, (B) pseudo-second-order, and (C) intraparticle diffusion model (30 to 180 min, pH 4, dosage of 1.6 g/L, T = 55 °C). (D) Plot to obtain thermodynamic parameters for adsorption of Pb2+ by MC/TiO2 NP nanocomposite.
Figure 7
Figure 7
Effect of competing ions on Pb2+ ion adsorption.
Scheme 3
Scheme 3. Adsorption Mechanism of Pb2+ by Using the MC/TiO2 NP Nanocomposite
Scheme 4
Scheme 4. Blood Fingerprint Image Details by Pb2+-MC/TiO2 NP Nanocomposite on the Aluminum Sheet under Daylight Conditions
Figure 8
Figure 8
Photographs of blood fingerprints before application of the Pb2+-MC/TiO2 NP nanocomposite on (a) mirror, (b) aluminum sheet, (c) glass slides. Enhanced blood fingerprint using the Pb2+-MC/TiO2 NP nanocomposite on (d–-f) mirror, (g,h) aluminum sheet, (i) glass slide.
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