Preparation and Characterization of Raw and Inorganic Acid-Activated Pine Cone Biochar and Its Application in the Removal of Aqueous-Phase Pb2+ Metal Ions by Adsorption

In this work, the synthesized slow pyrolysis biomass pine cone (Pinus radiata)–based biochar was acid activated, characterized, and tested for its effectiveness in the adsorptive removal of aqueous-phase Pb2+ metal ions. The adsorbent surface modification was conducted by treatment with H2SO4 and H3PO4 and was characterized by BET surface area, pore volume, pore size, C-H-N-S analysis, the presence of various functional groups through FT-IR (Fourier Transform- Infrared), the crystallinity of the material and presence of minerals by XRD (X-ray diffraction spectrum), and surface morphology by FESEM. The specific surface area after acid modification has been increased from 145 to 472 m2/g. Also, acid treatment causes an increase of the COO− functional group on the adsorbent surface which are responsible for adsorption. All three types of biochar, namely BC (raw biochar without modification), AC1 (modified by H3PO4), and AC2 (modified with H2SO4) were used for the removal of aqueous-phase Pb2+ by batch adsorption and compared. Various physicochemical process parameters such as initial solution pH, initial metal ion dose or adsorbate concentration, adsorbent dose, and system temperature and their effect on metal ion adsorption mechanism have been identified and optimized here. Maximum Pb 2+ adsorption capacities were obtained as 251, 283 mg/g and 321 mg/g for BC, AC1, and AC2 respectively which are very much comparative with other reported adsorbents including commercial activated carbon under similar experimental conditions. This study indicated that pine cone biochar was an environment-friendly and cost-effective adsorbent in sustainable solution for water and wastewater treatment.