Palm leaves based biochar: advanced material characterization and heavy metal adsorption study

The current report provides the synthesis and characterization of palm tree leaves biochar (PL-BC) prepared by simple thermal pyrolysis at 550 °C, which was then used for the elimination of lead and chromium from aqueous solution. An advanced material characterization was conducted by XPS, SEM, EDS, and FT-IR for the raw and spent PL-BC. Moreover, detailed surface chemical state analysis and identification of the chemical species was conducted by the XPS. The XPS surface analysis revealed high carbon content 78.5% while the BET surface area was 21.6 m²/g. The surface oxygen content was about 15.7% suggesting the abundance of oxygen functional groups onto the PL-BC. The adsorption results demonstrated that the removal of lead and chromium by PL-BC obeyed to Freundlich model, while kinetics data obeyed to pseudo-second order model. Furthermore, the Freundlich maximum adsorption uptakes for lead and chromium were 79.2 mg/g and 51.9 mg/g, respectively. The reusability studies demonstrated that more than 64% of the initial remediation efficiency of lead and chromium can be achieved after five adsorption/desorption cycles. Moreover, the PL-BC was able to reduce the lead and chromium content from injected actual brackish water of 1 mg/L to the international allowable limits of drinking water (˂50 µg/L). The remediation of lead and chromium by PL-BC was controlled by physical and chemical adsorption processes and dominated by complexation, precipitation, and ion exchange. These outcomes disclose the mechanism of lead and chromium removal by PL-BC and provide a sustainable solution of utilizing agriculture waste in water treatment. Graphical Abstract: (Figure presented.)