Synthesis of activated carbons using custard apple seeds and their application in the adsorption of textile dyes

This work describes the preparation of five activated carbons from a vegetable waste: custard apple seeds ( Annona cherimola). ). All carbons were chemically activated with phosphoric acid. Three of them were calcinated at 673 K (CarChiQ, CarChiQE, and CarChiQC) and the other two (CarChiQE600 and CarChiQC600) at 873 K for three hours. The carbons were characterized by nitrogen adsorption, methylene blue number, bulk density, scanning electron microscopy, and infrared spectroscopy. In addition, the point of zero charge indicated the acid character of the carbons. To establish the contact time between the solutions of dye and the carbons, the adsorption kinetics of methylene blue dye was followed. The adsorption kinetics for all the carbons fit the pseudo second order model. The adsorption of aqueous solutions containing anionic and cationic dyes with an initial concentration of 300 mg/dm3 3 was studied. It was found that, using CarChiQ, basic dyes were adsorbed in percentages ranging between 82 and 99.9 %; with CarChiQE, between 65 and 92 %; and using CarChiQC, CarChiQE600, and CarChiQC600, the adsorption almost reached 100 %. The acid dye was adsorbed in a smaller proportion, but in CarChiQE600 and CarChiQC600, its adsorption was total. A wastewater containing textile dyes was treated, and its quality was improved after the adsorption treatment. The chemical oxygen demand was reduced up to 76 % and its color until 98 %.