Evaluation of Three Biomaterials from Coconut Mesocarp for Use in Water Treatments Polluted with an Anionic Dye

Abstract

Coconut consumption leads to the generation of a large number of fibrous residues such as epicarp and mesocarp. In this study, bioadsorbents were prepared from coconut shells (CS), coconut cellulose (CC) and treated coconut cellulose (MCC) with cetyl trimethyl ammonium chloride (CTAC) for the elimination of Congo red (CR) in a watery solution. The impact of the adsorbent quantity (15, 25 and 35 mg) and initial concentration (40, 70 and 100 mg/L) were evaluated. Fourier transform infrared spectra (FTIR) confirmed the existence of OH−, C=O, COOH and CH2 groups in the adsorbents as well as the deformation of the bands between 3400 and 3800 cm−1 after the adsorption of CR, which was attributed to its capture in the bioadsorbent. From the bromatological analysis, a content of 48.94% lignin, 35.99% cellulose and 10.51% hemicellulose was found. SEM images showed a lignocellulosic essential surface origin for all adsorbents with presence of folds, roughness of an irregular exposed area and fibrous filaments. The average particle size was 0.45 mm and adsorbents had a mean porosity of 0.58. Increasing the initial concentration had a beneficial influence on the removal efficiency of CR, achieving a 99.9% removal with MCC. CS showed slow kinetics in the initial stages whereas CC and MCC achieved 78% and 99.98% removal at 120 min, respectively; an equilibrium was reached at 480 and 20 min, respectively. MCC, CC and CS achieved a maximum qe of 256.12 mg/g, 121.62 mg/g and 17.76 mg/g, respectively.