Valorization of coconut husk into biochar for lead (Pb ²⁺ ) adsorption

Abstract Potentially toxic element contamination in water poses a significant environmental concern. Lead in divalent form (Pb 2+ ) is considered as highly toxic due to its wide number of applications in synthetic paint, metal smelting, and industrial applications and is harmful to the environment and public health. Researchers are exploring biochar production from biomass such as coconut husk biochar (CHBC) to achieve the objectives of sustainable development and circular economy. Thus, in this current study, we focused on the production, effectiveness, and characterization of CHBC as a cost-effective adsorbent for the elimination of Pb 2+ . In this regard, biochar was optimized at different temperatures of 200°C, 400°C and 600°C, and the best yield was obtained at 600°C. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) studies were conducted for further characterization, which showed an increase in the crystallinity of biochar from 56.4% to 64.3%, suggesting that the prepared biochar is highly porous. The prepared biochar was leveraged for the removal of Pb 2+ from water using varying concentrations, temperatures, and pH conditions, and the analysis was carried out using ultraviolet–visible (UV–vis) spectroscopy. The optimal parameters were found to be a molar concentration of 0.0125 M, a catalyst dose of 500 mg, room temperature, and a pH of 6. Adsorption follows Langmuir and Temkin isotherms, which appear to be well suited in the adsorption process based on the correlation coefficient of the linear graph ( R 2 = 0.97 and 0.99) and pseudo-first-order kinetics, with a correlation coefficient of R 2 = 0.546. The empirical results indicate that the usage of a pseudo-first-order kinetics model is well-matched in the adsorption process, and the evaluation was done by using UV–vis spectroscopy, while characterization was carried out using SEM–energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, and XRD. Thus, the prepared biochar has been demonstrated to be an efficient platform for lead decontamination, paving the way for future researchers to explore and develop more effective techniques. This approach aligns with sustainable development goals and contributes to improved waste management practices.