The widespread application of herbicides in modern agriculture has led to a growing problem of water contamination, posing significant risks to both ecosystems and human health. Among these pollutants is 2,4-dichlorophenoxyacetic acid (2,4-D), one of the most common synthetic herbicides used globally, particularly for crops like wheat, corn, and rice. Unfortunately, studies show that over 99.9% of applied 2,4-D fails to reach the target plants, persisting in the environment and leachingLeaching is the process where nutrients are dissolved and carried away from the soil by water. This can lead to nutrient depletion and environmental pollution. Biochar can help reduce leaching by improving nutrient retention in the soil.   More into aquatic systems. To combat this issue, researchers are constantly investigating efficient and low-cost water treatment technologies. A novel study published in Scientific Reports by Mozhdeh Keramatzadeh, Majid Ehteshami, and Afshin Takdastan presents a sustainable and highly effective solution: an adsorbent synthesized from date seed waste activated with sodium hydroxide (NaOH).

The foundation of this solution is the valorization of abundant agricultural waste. Khuzestan Province in southwest Iran, a major agricultural region, generates a considerable amount of discarded date pits due to extensive date palm cultivation. This waste biomassBiomass is a complex biological organic or non-organic solid product derived from living or recently living organism and available naturally. Various types of wastes such as animal manure, waste paper, sludge and many industrial wastes are also treated as biomass because like natural biomass these More was converted into biocharBiochar is a carbon-rich material created from biomass decomposition in low-oxygen conditions. It has important applications in environmental remediation, soil improvement, agriculture, carbon sequestration, energy storage, and sustainable materials, promoting efficiency and reducing waste in various contexts while addressing climate change challenges. More via pyrolysisPyrolysis is a thermochemical process that converts waste biomass into bio-char, bio-oil, and pyro-gas. It offers significant advantages in waste valorization, turning low-value materials into economically valuable resources. Its versatility allows for tailored products based on operational conditions, presenting itself as a cost-effective and efficient More at 500±50°C. While the raw biochar showed limited intrinsic porosityPorosity of biochar is a key factor in its effectiveness as a soil amendment and its ability to retain water and nutrients. Biochar’s porosity is influenced by feedstock type and pyrolysis temperature, and it plays a crucial role in microbial activity and overall soil health. Biochar More and surface area , chemical activation with NaOH proved transformative. The activation process significantly enhanced the material’s properties, increasing the surface area to 236.42 m2g⁻¹ and introducing additional oxygen-containing functional groups, which are vital for chemical interactions with the pollutant. The morphological analysis confirmed this success, as the smooth raw surface became noticeably rougher and fissured with numerous pores after the NaOH treatment.

The enhanced material demonstrated vastly superior performance. Under optimized conditions, the NaOH-activated biochar achieved a high 2,4-D removal efficiency of 89.3% in just 60 minutes. In stark contrast, the raw, unactivated biochar could only manage 33.6% removal, and it took a longer 120 minutes to reach its peak efficiency. This notable improvement underscores the critical role of the NaOH activation in improving surface chemistry and porosity. The highest removal was achieved at a solution pH of 4. This is because the pH of the water influences the charge of both the adsorbent surface and the herbicide molecule. At this slightly acidic pH, the biochar surface becomes positively charged, creating a strong electrostatic attraction for the negatively charged 2,4-D molecules in the water.

Modeling the adsorption process revealed key aspects of the removal mechanism. The experimental data fit the Langmuir model best, which suggests that the herbicide molecules form a single, uniform layer on the biochar surface. The maximum adsorption capacity determined by this model was 62.11 mg of 2,4-D per gram of biochar. Furthermore, the kinetic data was best described by the pseudo-second-order model, indicating that the speed of the removal process is primarily limited by chemisorption, a process involving chemical bonding or valence electron exchange between the herbicide and the functional groups on the biochar surface. Thermodynamic analysis confirmed the process is spontaneous and endothermic, meaning it is naturally favorable and is actually enhanced by warmer temperatures, which is a practical advantage for field applications in warm regions.

Compared to other biochars, the date seed-derived material is highly competitive. While some other biochars, like ginkgo leaf biochar, report higher adsorption capacities, they often require more chemically intensive and costly activation processes. The NaOH activation method used here offers a strong balance of high performance, low cost, and sustainability, affirming its suitability for large-scale, cost-effective remediation of 2,4-D contaminated water. The material also showed good reusability, maintaining over 80% of its initial removal efficiency for up to three cycles, though performance declined in the fourth cycle. This low-cost, locally available adsorbent presents a promising, eco-friendly solution for managing agricultural waste and safeguarding water resources.

Source: Keramatzadeh, M., Ehteshami, M., & Takdastan, A. (2025). Efficient removal of 2,4-D using NaOH-activated date seed Biochar with adsorption behavior, kinetic and isotherm modeling, and process optimization. Scientific Reports.