Abstract
In this study, shea residues (Vitellaria paradoxa) dumped in the wild by the units processing almonds into butter were used in the production of activated carbons. Shea nut shells harvested in the locality of Baktchoro, West Tandjile Division of Chad were used as a precursor for the preparation of activated carbons by chemical activation with phosphoric acid (H3PO4) and sulphuric acid (H2SO4). Central Composite Design (CCD) was used to optimize the preparation conditions, and the factors used were concentration of activating agent (1 - 5 M), carbonization temperature (400°C - 700°C) and residence time (30 - 120 min). The studies showed that at optimal conditions the yield was 51.45% and 42.35%, while the iodine number (IN) was 709.45 and 817.36 mg/g for CAK-P (phosphoric acid activated carbon) and CAK-S (sulphuric acid activated carbon) respectively. These two activated carbons (ACs) which were distinguished by their considerable iodine number, were variously characterized by elementary analysis, pH at the point of zero charge (pHpzc), bulk density, moisture content, Boehm titration, Fourier transform infrared spectroscopy, BET adsorption and scanning electron microscopy. These analyses revealed the acidic and microporous nature of CAK-P and CAK-S carbons, which have a specific microporous surface area of 522.55 and 570.65 m2·g−1 respectively.
Highlights
A major environmental problem facing agro-food industries is their inability to efficiently manage the residues and by-products generated during the primary processing of raw materials
A triacid and diacid were used as activating agents in the preparation of activated carbons (ACs) using shea residues (Vitellaria paradoxa) as precursors
Central composite design was used to study the influence of preparation parameters, concentration of activating agents, carbonization temperature and residence time, on expected responses, yield and iodine number
Summary
A major environmental problem facing agro-food industries is their inability to efficiently manage the residues and by-products generated during the primary processing of raw materials. The processing of agricultural commodities generates huge quantities of lignocellulosic residues that are disposed of by land filling or incineration. These practices have a negative effect on man and his environment. Open-air incineration generates substances which are toxic to humans and constitute greenhouse gases that have damaging effects on the climate [1]. It is because they are wrongly considered as wastes that these agricultural residues are treated in this way. Of these alternative treatments of the lignocellulosic residues, the transformation into activated carbons is more flexible; with chemical activation significantly reducing the energy cost of the process
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