Soil & Water Res., 2026, 21(1):52-65 | DOI: 10.17221/106/2025-SWR

Ca–Mg–Al LDH-modified wheat straw biochar for efficient lead chemisorption from aqueous solution: Insights from isotherm and kinetic analysesOriginal Paper

Muhammad Tahir Amin ORCID...^1*, Abdulrahman Ali Alazba^2,3, Muhammad Shafiq³, Aftab Ahmad Khan¹, Muhammad Muhitur Rahman¹

¹ Department of Civil and Environmental Engineering, College of Engineering, King Faisal University, Al-Ahsa Saudi Arabia

² Department of Agricultural Engineering, College of Food & Agriculture Sciences, King Saud University, Riyadh, Saudi Arabia

³ Alamoudi Water Research Chair, King Saud University, Riyadh, Saudi Arabia

This study reports layered double hydroxides (LDHs) modified wheat straw biochar (W-B), denoted as (LDH/W-B), as an efficient adsorbent material for removal of lead (Pb²⁺) ions from aqueous solution. This study also juxtaposes the adsorptive performance of LDH/W-B with W-B for Pb²⁺ removal. W-B was prepared via pyrolysis of wheat straw in a muffle furnace, using a controlled heating rate of 5 °C per min to reach 600 °C over a duration of three hours. Subsequently, LDH/W-B was synthesised using the co-precipitation method. Both resulting adsorbents were characterised for surface morphology and functional groups by means of scanning electron microscope (SEM) and Fourier transform infrared (FTIR), respectively. The influence of key adsorption parameters on the adsorption efficiency of W-B and LDH/W-B was systematically evaluated. At 60 min, the maximum Pb²⁺ removal efficiency was observed to be 78.21% for W-B and 92.4% for LDH/W-B. An increase in adsorbent dosage from 0.05 to 0.7 g and at a contact time of 1 h further enhanced Pb²⁺ removal, achieving efficiencies of 97% for W-B and 99% for LDH/W-B. The optimal conditions for maximum Pb²⁺ removal were determined to be 0.3 g of adsorbent (W-B and LDH/W-B), an initial heavy metal concentration of 10 mg/L, and a contact time of 1 h. Pb²⁺ removal data of W-B and LDH/W-B best fitted to the Langmuir isotherm and pseudo-second order kinetic model, which confirmed the dominance of chemisorption of Pb²⁺ ions. Additionally, the maximum theoretical adsorption capacity for Pb²⁺ is close to the experimentally obtained values, suggesting that the adsorption of Pb²⁺ primarily occurs through monolayer formation on the surface of both adsorbents. Overall, this study demonstrates that LDH/W-B is a highly promising adsorbent for Pb²⁺ removal in wastewater treatment applications.

Keywords: activated biochar; adsorption; layered double hydroxides; pseudo-second-order

Received: August 23, 2025; Revised: December 7, 2025; Accepted: January 6, 2026; Prepublished online: January 20, 2026; Published: January 26, 2026  Show citation