Congo red loaded carbon aerogel/polypyrrole spent adsorbent in combination with polypyrrole supported carbon aerogel composite adsorbent for removal of Congo red dye from wastewater and for the reuse of latent fingerprint detection

In this study, a Congo red loaded carbon aerogel/polypyrrole (CR-CA/PPy) spent adsorbent in combination with a polypyrrole supported carbon aerogel composite adsorbent was used for more effective removal of Congo red (CR) dye from wastewater and for reuse in latent fingerprint detection. By wrapping CA in the PPy polymer, a carbon aerogel coated polypyrrole (CA/PPy) composite was created by an adsorption process. To verify the successful formation of the CA/PPy composite various instrument methods were used including Ultraviolet–visible spectroscopy (UV–visible), Fourier Transform Infrared Spectroscopy (FT-IR), X-ray diffraction patterns (XRD), scanning electron microscope (SEM), Transmission electron microscopy (TEM), and Brunauer-Emmett-Teller (BET). The results showed that the specific surface area (7.68 m²/g) of the CA/PPy composite was greater than that of the base materials. Congo red (CR) dye was removed using a batch adsorption approach with this CA/PPy composite as the adsorbent, reaching adsorption equilibrium at pH 6.5 in 180 min. Additionally, the Freundlich isotherm model provided a good fit to the adsorption process occurring on the CA/PPy composite's heterogeneous surface. It was shown that the Freundlich isotherm model more accurately depicted the adsorption processes than the Langmuir isotherm model, with a maximum adsorption capacity of 324.64 mg/g, a high coefficient of determination (R² = 0.9999), and an adsorption intensity factor (1/n = 0.9905). The pseudo-second-order kinetic model most closely matched the adsorption kinetics data. The adsorption of CR dye utilizing the CA/PPy composite showed that the adsorption process was both spontaneous and endothermic, as indicated by the ΔG⁰ and ΔH⁰ values respectively, and the endothermic nature was clearly evident by the most favorable adsorption of CR at 45 °C. It is interesting to note that the CA/PPy composite demonstrated superior reusability during four repeated adsorption/desorption cycles. In order to control pollution, this composite is practically applicable for the adsorptive removal of contaminants such as CR dye from wastewater. Additionally, by employing the powder dusting approach under visible light irradiation, CR-CA/PPy spent adsorbent powder was used for latent fingerprint detection on various porous and non-porous substrates. Moreover, aged and multiple LFP detection tests were conducted on this spent adsorbent powder. As a result, it has been determined that CR-CA/PPy spent adsorbent powder is superior to other fingerprint powders and lowers environmental secondary pollution caused by adsorption treatment methods.