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Lead (Pb(II)) contamination in water is a critical environmental issue due to its severe toxicity and pervasive presence. Traditional methods for removing lead from wastewater, while effective, are often neither economical nor environmentally friendly. Recent research has highlighted the use of biochar, a carbon-rich material, as a promising alternative due to its affordability, efficiency, and environmental benefits.

Biochar is produced from organic materials, in this case, Prosopis juliflora, a common tree species. This research explored the enhancement of biochar’s lead adsorption capacity through modification with phosphoric acid (H3PO4) and nitric acid (HNO3). These modifications aim to leverage the inherent properties of biochar such as its large surface area and diverse functional groups, thus improving its efficiency in lead removal from wastewater.

The study employed a variety of analytical techniques to characterize the biochar before and after modification, including X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, scanning electron microscopy (FE-SEM), thermogravimetric analysis (TGA), and elemental analysis. A batch experiment was conducted to evaluate the influence of various parameters on the efficacy of lead removal, including adsorbent dosage, contact time, initial lead concentration, and solution pH.

Results demonstrated that the acid-modified biochars significantly outperformed the pristine biochar in adsorption capacity. Specifically, the nitric acid-modified biochar exhibited the highest adsorption capacity at 18.72 mg g^−1, followed by the phosphoric acid-modified at 17.32 mg g^−1, and the pristine at 10.98 mg g^−1. The adsorption process was found to fit best with the Freundlich isotherm model, indicating a multilayer adsorption on a heterogeneous surface. Furthermore, the pseudo-second-order kinetic model provided the best correlation for the adsorption kinetics, suggesting chemisorption as the predominant mechanism.

This study not only supports the use of acid-modified biochar as a highly effective and sustainable method for removing lead from wastewater but also contributes to resource management and environmental remediation by providing a beneficial use for agricultural waste products. The enhanced capacity and eco-friendly nature of modified biochar make it a superior alternative to conventional adsorbents, aligning with the goals of sustainability and pollution reduction.

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