Removal of reactive black 5 dye using modified chitosan-pandan adsorbent

Abstract

There has been increased interest of chitosan as a dye adsorbent. Nonetheless, the chitosan tend to form bonding between their monomer chains that result in a rigid structure which affects its capability for dye adsorption. This is why there are many recent studies on modified chitosan through various modification in order to overcome the limitation. But, most modifications involve chemical additive agents as well as complex procedures that are conducted under strong conditions. Not much research consider low-cost organic materials as modifying agents. The purpose of this work is to investigate the performance of chitosan modified with pandan leaves in the adsorption of reactive black 5 (RB5). Modified chitosan-pandan (MCP) were synthesised by simple wet impregnation using polyphenols from extracted pandan oil under mild condition. MCP was characterised using the scanning electron microscopy, Fourier transform infrared spectroscopy and Brunauer-Emmett-Teller surface area analysis. A batch adsorption was conducted to study the effect of retention time (0-40 min), initial dye concentration (100-1000 mg/L), pH (3-11), temperature (25-80 °C) and dosage of adsorbent (0.01-1.0 g), and to determine the optimum process conditions. Kinetics, isotherm and thermodynamics evaluation were also performed on the adsorption data. The results of MCP adsorption showed outstanding dye removal, with almost 100% under the optimum conditions (30 min, 200 mg/L of RB5, pH 7 and 0.1 g of MCP). The adsorption data fitted well to the pseudo-second order model, indicating the role of chemisorption with the influence of intraparticle diffusion. For isotherm study, the data are best fitted to the Langmuir model (R2 = 0.95) with the maximum adsorption of 115.58 mg/g. A thermodynamics analysis showed that the adsorption was endothermic, occurred spontaneously and feasible. MCP is capable to be regenerated up to 5 times with percentage removal above 50% by only washing with distilled water. In conclusion, a satisfactory performance of MCP in RB5 removal was successfully demonstrated, can be used as a new promising adsorbent for the removal of dyes from textile wastewater.