Carbon nanosheets coated on zirconium oxide nanoplate nanocomposite for Zn²⁺ ion adsorption and reuse of spent adsorbent for fingerprint detection

This work highlights a novel method for the synthesis of carbon nanosheets coated on zirconium oxide nanoplate (CNS/ZrO₂NPs) nanocomposite that is used as an adsorbent for Zn²⁺ ions removal from water. CNS/ZrO₂NPs nanocomposite was prepared using CNS and ZrO₂NPs by a hydrothermal method. This nanocomposite proved to be a good adsorbent for Zn²⁺ ion uptake at maximum pH of 8 and dosage of 20 mg. The Temkin isotherm model represented the adsorption process followed by the Langmuir isotherm with a maximum adsorption capacity of 606.06 mg g⁻¹, above other adsorbents that have been reported for the removal of zinc ions. The adsorption kinetic process was best described by the pseudo-second-order kinetics, and it was found that the adsorption followed a chemisorption process. The thermodynamic parameters, such as enthalpy (ΔH), Gibbs free energy (ΔG), and entropy (ΔS), revealed that the adsorption was exothermic, spontaneous, and not random during the process. This metal-loaded adsorbent Zn²⁺-CNS/ZrO₂NPs nanocomposite furthermore was reused in latent fingerprint detection and did demonstrate good selectivity and sensitivity on different surfaces by two donors. Therefore, Zn²⁺-CNS/ZrO₂NPs nanocomposite may be reutilized as a good fingerprint marking agent in latent fingerprint (LFP) identification to circumvent secondary environmental pollution by the release of a spent adsorbent.