Coconut dregs as potential biosorbents for treatment of dye

Abstract

In this study, the potential use of coconut dregs as the biosorbent for the removal of Methylene Blue (MB) (basic dye) and Brilliant Red Remazol (BRR) (acidic dye) was investigated. The effects of adsorption time, adsorbent dosage, pH, and initial dye concentration on coconut dregs adsorption for MB dye and BRR dye were investigated during the batch mode adsorption study. The results indicated that the amount of dye adsorbed on the coconut dregs increased with increasing dye concentration, adsorbent dosage, and adsorption time. However, both MB and BRR dyes favor different pH for the adsorption process. The adsorption capacity of MB dye increased with increasing pH while the adsorption capacity of BRR dye increased with decreasing pH. For Methylene Blue dye, the most effective of color removal was optimum at pH 11, contact time of 240 min, dosage of 0.25 g adsorbent, and with initial dye concentration of 50 mg/L. Meanwhile, for Brilliant Red Remazol dye, the most effective of color removal was optimum at pH 2, contact time of 180 min, dosage of 0.25 g adsorbent, and with initial dye concentration of 50 mg/L. The Langmuir and Freundlich adsorption models were used to evaluate the isotherm constants at 25°C. The equilibrium data for both dyes fitted very well with Langmuir Isotherm equation giving maximum monolayer adsorption capacity as high as 5.7208 mg/g and 3.7636 mg/g for Methylene Blue Dye and Brilliant Red Remazol dye, respectively. The modeling of the kinetics of dyes adsorption onto coconut dregs was investigated using two common models; the pseudo-first-order model and pseudo-secondorder model. Methylene Blue dye follows the second-order-adsorption model while the Brilliant Red Remazol dye follows the first-order-adsorption model.