Evaluation of Adsorbent Biomaterials Based on Coconut Mesocarp for Treatment of Wastewater Contaminated with Tartrazine Dye

Abstract

The presence of synthetic dyes in industrial wastewater poses significant environmental and health concerns due to their persistent nature and potential toxicity. Tartrazine is a synthetic yellow dye known for its stability and resistance to conventional treatment methods. As a result, its discharge into natural water bodies can lead to adverse ecological impacts and can jeopardize public health. The objective of this work was to functionalize coconut shells (CSs), coconut cellulose (CC), and modified coconut cellulose (MCC) bioadsorbents with cetyl trimethyl ammonium chloride (CTAC) for their use in the elimination by adsorption of the dye tartrazine in aqueous solutions. CC was synthesized through a double extraction with sodium hydroxide, and a chemical treatment was performed with CTAC at 100 mmol L−1. The final dye concentration was determined through UV-Vis at 500 nm. An FTIR analysis showed multiple active sites, represented in groups such as hydroxyl, COO-, NHx-, and hydrocarbon compounds. Increasing the initial concentration had a positive effect on the efficiency of the process, reaching 99% removal with an adsorption capacity of 11.89 mg/g at equilibrium using MCC. The test showed that equilibrium was reached after 30 min. Initially, the removal of the dyes was rapid, about 97% of the contaminant being removed in the first 5 min. The Langmuir and Freundlich models were satisfactorily fitted to the adsorption isotherm, showing physical and chemical adsorption. It can be concluded that MCC is a promising bioadsorbent for the removal of tartrazine dye in aqueous solutions.