The improvement of indigo carmine dye adsorption by Terminalia catappa shell modified with broiler egg white

Indigo carmine (IC) is a highly toxic dye that is present in industrial wastewater and leads to serious environmental issues. This synthetic dye can harm ecosystems even at low concentrations. In the present research, Terminalia catappa (TC) shell was modified using the egg white (EW) of broiler chicken (TC-EW) to increase its adsorption capacity for IC removal. The optimum conditions were reached at the pH 2, initial concentration of IC 800 mg/L, contact time 30 min, particle size (≤ 36 μm), and agitation speed of 100 rpm in 25 mL IC dye containing a biosorbent dose of 0.1 g at the temperature of 27 °C. The maximum adsorption capacity of TC-EW to adsorb IC was 106.98 mg g−1. The equilibrium behavior was fit to Langmuir isotherm showing monolayer adsorption. The kinetics of adsorption was fit to pseudo-second-order showing chemical interactions through the sharing or electron exchange of the dye compound and the biosorbent. Mechanism of IC into the TC-EW is by electrostatic attraction, pore diffusion, hydrogen bonding, ion exchange, and π-π interaction. The analysis of the process thermodynamic revealed that it was endothermic and spontaneous at temperature 300–318 K. The effective desorption of IC onto TC-EW shell was achieved using 30% glycerol in alkaline condition and can be re-used for up to 3 cycles.