Characterization and Kinetic Analysis of Activated Flamboyant Tree Pod (Delonix regia) Biochar for Crude Oil-Contaminated Water Treatment

Abstract:

Water pollution causes about 1.4 million deaths annually, and in Nigeria, especially in rural areas and the Niger Delta, millions lack access to clean water due to crude oil contamination. This study investigates using carbonized Flamboyant (Delonix regia) pods as a sustainable, low-cost adsorbent for removing petroleum hydrocarbons from contaminated water, promoting agricultural waste valorization and pollution reduction. Water samples collected from Obiakpor in Port Harcourt, Nigeria, were found to contain 75.22 mg/L of total petroleum hydrocarbons (TPH) and were subsequently used to evaluate the efficiency of the prepared adsorbent. Activated carbon was prepared by washing, drying, carbonizing the pods at 550 °C, chemically activating with KOH, neutralizing, then drying and sieving for uniformity. Carbonization yielded 30.2%, with proximate analysis showing low moisture (1.86%), moderate ash (4.94%), and high volatile matter (77.81%), favoring thermal stability and pore formation. Scanning Electron Microscopy (SEM) and Brunauer–Emmett–Teller (BET) revealed a highly porous structure with an average pore diameter of 20 μm and a large surface area of 226.4 m²/g. X-ray Diffraction (XRD) confirmed a semi-crystalline structure dominated by graphite (36 wt.%) and silicate minerals, enhancing mechanical strength and π–π interactions. Thermogravimetric Analysis (TGA showed that thermal stability was maintained between 300–500°C. Adsorption tests showed TPH removal increased with adsorbent dosage up to 0.2 g, reaching equilibrium afterward. The Freundlich isotherm best described the adsorption (R² = 0.9104), indicating multilayer adsorption on a heterogeneous surface, supported by high constants (K_f = 166.36; n = 2.35). Kinetic studies indicated rapid adsorption within 25 minutes, fitting the pseudo second order model (R² = 0.9575). These findings confirm that carbonized Flamboyant tree pods (FTP) are effective, renewable, and thermally stable adsorbents for petroleum-contaminated water treatment.

• Periodical: Engineering Chemistry (Volume 12)
• Pages: 25-36
• DOI: https://doi.org/10.4028/p-JxUQJ9
• Online since: December 2025
• Authors: Ayodunmomi Esther Olowofoyeku*, Daniel Gbenga Adekanmi
• Keywords: Activated Carbon, Adsorption, Delonix Regia, Flamboyant Tree, Remediation, Total Petroleum Hydrocarbon

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