Nitric acid-treated Luffa cylindrica seeds as a sustainable biosorbent: Characterization and fixed-bed column performance for simultaneous removal of Ni (II), Cu (II), and Zn (II) from aqueous solutions
1 Department of Chemical/Petrochemical Engineering, Rivers State University, Nigeria.
2 Department of Chemical Engineerng University of Uyo, Uyo, Nigeria.
Research Article
Open Access Research Journal of Engineering and Technology, 2026, 11(01), 001–014.
Article DOI: 10.53022/oarjet.2026.11.1.0052
Publication history:
Received on 03 June 2026; revised on 12 July 2026; accepted on 15 July 2026
Abstract:
The escalating contamination of water resources by toxic heavy metals demands the development of cost-effective and sustainable remediation technologies. This study investigated the application of nitric acid-treated Luffa cylindrica (LC) seeds as a novel biosorbent for the simultaneous removal of Ni(II), Cu(II), and Zn(II) ions from aqueous solutions using a continuous fixed-bed column system. The LC adsorbent was produced at a carbonation temperature of 105 degrees C and comprehensively characterized using Fourier Transform Infrared (FTIR) spectroscopy, Scanning Electron Microscopy (SEM), and Brunauer-Emmett-Teller (BET) analysis. The BET surface area, pore volume, pore diameter, and bulk density were determined as 23.971 m squared/g, 0.011 cc/g, 2.402 nm, and 0.34 g/cm cubed, respectively. FTIR analysis identified hydroxyl, carboxyl, and carbonyl functional groups as active binding sites for metal chelation. The effects of column bed height (5, 7.5, 10 cm), injection flow rate (5, 10, 15 mL/min), and initial metal concentration (10, 20, 30 g/L) on adsorption performance were systematically evaluated. Results demonstrated that increasing bed height significantly enhanced metal removal efficiency, achieving maximum removals of 83.07% for Ni(II), 51.66% for Cu(II), and 55.73% for Zn(II) at 10 cm bed height with 5 mL/min flow rate. Conversely, elevated flow rates and larger adsorbent particle sizes (above 75 micrometer) reduced removal efficiency due to decreased residence time and increased diffusion resistance. The optimal operating conditions were established as 10 cm bed height, 5 mL/min flow rate, and 75 micrometer particle size. The pseudo-second-order kinetic model provided the best fit (R squared = 1.000), indicating chemisorption as the rate-controlling mechanism. This study establishes LC seeds as a promising, eco-friendly, and economically viable biosorbent for heavy metal remediation in wastewater treatment applications.
Keywords:
Luffa cylindrica; Biosorption; Heavy metals; Fixed-bed column; Characterization; Nickel; Copper; Zinc; Wastewater treatment
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