Efficient removal of 2,4-D using NaOH-activated date seed Biochar with adsorption behavior, kinetic and isotherm modeling, and process optimization

The herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) is highly mobile and resistant to degradation, posing serious ecological and human health risks in aquatic environments. In this study, we synthesized an efficient and sustainable adsorbent from date seed biomass through NaOH activation. The prepared biochar was characterized using FTIR, SEM, XRD, BET, and EDS analyses, which confirmed major improvements in surface functionality, pore structure, and specific surface area (236.42 m² g^-1). Under optimized batch conditions (pH = 4, dose = 2 g L^-1, contact time = 60 min), the NaOH-activated biochar achieved a removal efficiency of 89.3%, while the raw biochar reached only 33.6% at its optimum condition. Adsorption followed the Langmuir isotherm model (q_m = 62.11 mg g^-1; R² = 0.951) and the pseudo-second-order kinetic model (R² = 0.997), indicating monolayer chemisorption as the dominant mechanism. Thermodynamic results confirmed that the process is spontaneous and endothermic. This work demonstrates the potential of low-cost, locally available date seed waste as a sustainable resource for developing high-performance biochar. The proposed method provides a practical and eco-friendly solution for the treatment of herbicide-contaminated water, particularly in arid regions such as Khuzestan.