Optimized Preparation of activated carbon with high porosities based on puck shells (afrostyrax lepidophyllus) by response surface methodology and physico-chemical characterization
The Supplementary Material contains an in-depht description of handling protocol and tables presenting the experimental data which were used to plot certain curves of this paper. The handly protocol of activated carbon preparation, for the determination of iodine number, of Boehm method and for the pHZPC presents the meticulous details with which the manipulation was carried out and the assumptions used to determine the surface functions of the materials. Supplementary Table 1 give The Experimental design matrix generated by Statgraphics 5 plus software for any experiment of activated carbon preparation, Supplementary Table 2 gives the adsorption and desorption data of Nitrogen obtained for CRP, Supplementary Table 3 gives the adsorption and desorption data of Nitrogen obtained for CRB and Supplementary Table 4 gives The pH values of the filtrate obtained after mixing activated carbon with sodium chloride solutions at different pHinitial. (supplementary material).
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Chemical activation was used in this study to prepare activated carbons. For this purpose, phosphoric acid and sodium hydroxide were used as activating agents. The preparation of activated carbons was carried out as follows: 40 g of the crushed and dried CRN were mixed with 40 mL of activating agents of concentrations ranging from 0.5 to 1.5 mol/L. The CRN materials were impregnated for 24 hours with different activating agents to ensure contact with materials. The mixture was then filtered and the filtrate dried in an oven at 105 ˚C for 1 hour. In each case, the impregnated material was introduced into an electric furnace of mark HERAEUS that was set at temperatures ranging from 300 to 500˚C for residence times of 30 to 100 minutes, and a constant heating rate of 6 ˚C•min-1. In this study, the Box-Behnken design was chosen and the three factors investigated were: carbonization temperature (300 – 500 °C), the concentration of activating agent (0.5 - 2 mol.L-1) and carbonization time (30-100 min) and the response analyzed was the iodine number The Experimental design matrix generated by Statgraphics 5 plus software for any experiment is presented in supplementary table 1. In this work, the activating reagents used were H3PO4 and NaOH. The response surface methodology was used to develop a model which correlates the response to the three variables using a polynomial equation given by equation (1). American society of test and materials (ASTM) method D4607-94 was used to define the iodine number of the activated carbon samples produced.24 The iodine number of an activated carbon is used as an indicator of its relative porosity especially for pore sizes larger than 1nm 25. It measures the micropores contained in the AC. This was done by mixing 30 mL of iodine solution (0.02 N) with 0.1 g of activated carbon. The mixture was stirred for 3 hours and then filtered. After filtration, 10 mL of the filtrate were titrated with a sodium thiosulphate solution of concentration of 0.005 N using starch as colored indicator. . These two materials of considerable iodine number were characterized by pH at the point of zero charge (pHpzc), bulk density, moisture content, Boehm titration, Fourier transform infrared spectroscopy, BET method, Raman spectroscopy and scanning electron microscopy.