Study of the chemical characterization and pore distribution of activated carbons synthesized from local agri-food waste (Niger)

The objective of this study is the chemical characterization and pore distribution of activated carbons (ACs) synthesized from local agri-food waste (Niger) by chemical means. The selected waste materials are the shells of Balanites aegyptiaca (BA) (L.) Del. and Hyphaene thebaica (HT) (L.) Mart. Orthophosphoric acid (H3PO4) and sulfuric acid (H2SO4) are used as impregnation agents. Next, the mass yields of ACs after pyrolysis, iodine (I2) adsorption capacities, and methylene blue (MB) adsorption capacities are determined on the one hand, and total pore volume, cumulative pore volume (BJH), microporous volume, and average BET and BJH pore diameters are determined. Analysis of the results shows that the selected agri-food waste is a good precursor for the production of high-quality AC; it has very high cellulose content (67.6857% and 57.0571% for BA and HT, respectively). The pyrolysis temperature, concentration of the activating agent, and nature of the biomass have very significant effects on the yield of synthesized ACs. Activated carbons prepared by H3PO4 activation developed the best adsorption capacities. The total pore volumes range from CA-HT-1 (0.306531 cm³ g⁻¹) < CA-HT-2 (0.507390 cm³ g⁻¹) < CA-C (0.529036 cm³ g⁻¹) < CA-BA-1 (0.677426 cm³ g⁻¹) < CA-BA-2 (0.889648 cm³ g⁻¹). The average pore diameters range from CA-HT-1 (16.9788 Å) < CA-BA-1 (17.3617 Å) < CA-HT-2 (17.6995 Å) < CA-C (22.3516 Å) < CA-BA-2 (22.5136 Å). The pore diameters are essentially mesopores.