Properties of Biochar Prepared by Solar Pyrolysis and Its Adsorption of Cu<sup>2+</sup> in Water

This study investigates the potential of biochar produced via a solar pyrolysis system and its effectiveness in removing copper (Cu<sup>2+</sup>) ions from water, presenting a sustainable and energy-efficient method for biochar production and biomass recycling. Two common agricultural and livestock wastes, corn straw and cow dung, were used as raw materials to produce biochar. These materials underwent solar pyrolysis under limited oxygen conditions to produce biochar, which was then compared to biochar produced via traditional pyrolysis. The comparison involved elemental analyses, infrared spectroscopy, scanning electron microscopy, and specific surface area and pore size analysis to highlight differences in their physical and chemical properties. Adsorption experiments were conducted to evaluate the adsorptive capacity of biochar for copper ions (Cu<sup>2+</sup>) from water, determining the optimal pH conditions and underlying adsorption mechanisms. The findings reveal that biochar produced through solar pyrolysis exhibits similar properties and Cu<sup>2+</sup> adsorption capacities to those prepared by traditional methods. Specifically, cow dung biochar demonstrated a higher adsorption capacity for Cu<sup>2+</sup> compared to corn straw biochar. The Cu<sup>2+</sup> adsorption by corn straw biochar followed the Langmuir isothermal adsorption model and pseudo-second-order kinetic equation, whereas cow dung biochar conformed to the Freundlich isothermal adsorption model and pseudo-second-order kinetic equation. By demonstrating the comparable efficacy of solar pyrolysis biochar in heavy metal adsorption, this study highlights its potential for sustainable environmental remediation and biomass utilization.