Egusi seed shells (ESS) were used as precursor for the preparation of two activated carbons (ACs) following H 3 PO 4 and ZnCl 2 activation. The effect of factors controlling the preparation of ACs such as chemical activating agent concentration (2-10 M), activation temperature (400˚C-700˚C) and residence time (30-120 min) were optimized using the Box-Behnken Design (BBD). The optimized activated carbons based H 3 PO 4 (ACP) and ZnCl 2 (ACZ) were characterized by N 2 adsorption, elemental analysis, atomic force microscopy (AFM), Boehm titration and Fourier transformed infrared (FTIR) techniques. The specific surface area was found to be 1053.91 and 1009.89 m 2 •g −1 for ACP and ACZ respectively. The adsorbents had similar surface functionalities and were both microporous. The effect of various parameters such as initial pH, concentration, and contact time on the adsorption of nitrate ions on ACP and ACZ in aqueous solution was studied. ACZ demonstrated better adsorption capacity (8.26 mg•g −1) compared to ACP (5.65 mg•g −1) at the same equilibrium time of 20 min. The adsorption process was governed by a "physical interactions" phenomenon for both adsorbents.
The optimization conditions of preparation of activated carbons based Balanites aegytiaca shells by chemical activation was investigated. The effects of three parameters of preparation namely, the activation temperature (600-800 °C), impregnation ratio (1:4-3:8) and residence time (60-120 min) were thoroughly studied on the activated carbon yield (Yld, Y1), iodine number (ION,Y2) and methylene blue number (MBN, Y3) using the Methodology of Experimental Design (MED). The analysis of variance (ANOVA) under the experimental domain revealed that, the activation temperature of 800 °C, residence time of 02hrs and impregnation ratio of 1:2 were the optimum conditions of preparation leading to activated carbon yield of 23.0%, iodine number of 889.0 mg/g and methylene blue number of 9.7 mg/g. The polynomial equation showed that the three parameters were both synergetic and antagonistic on the responses retained. The higher values of iodine numbers obtained alongside the experimental matrix is an indication that the activated carbons so prepared were mainly microporous.
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