Production and characterization of activated carbon from pineapple stubble for removal of methylene blue and surfactants

Abstract

The objective of this work was to produce activated carbon from the agricultural waste known as pineapple stubble and to test its effectiveness in the removal of methylene blue and surfactants. Activated carbon was prepared using ZnCl2 and H3PO4 as activating agents and impregnation ratios of 2: 1 and 4:1 between the agent (mL) and the precursor (g) were evaluated. It was also investigated the need or not of a drying stage prior to carbonization. The produced activated carbon was characterized through FT-IR spectroscopy, X-ray fluorescence, N2 physisorption analysis, elemental analysis, and electron microscopy. Methylene blue adsorption tests were performed to determine the adsorption effectiveness of the different activated carbons produced. For such evaluation, a 23 factorial design was used, and statistical analysis determined that the activated carbon with the highest adsorption of methylene is produced under the following conditions: ZnCl2 as an activating agent, an impregnation ratio of 4:1, and with no drying step prior to carbonization. This produced activated carbon is also effective in the adsorption of the surfactant sodium dodecyl sulfate and for the surfactants present in the gray water obtained after washing clothes with commercial detergent. In these cases, removal efficiencies above 98 % were achieved. Concerning the characteristics of this activated carbon, it was observed a surface area of 685.5 m2/g, a total pore volume of 0.53 cm3/g, and an average pore diameter of 3.1 nm. Results achieved in the present study demonstrate that is possible to produce effective activated carbon for the removal of methylene blue and surfactants from agricultural waste such as pineapple stubble.