Use of methyl esterified eggshell membrane for treatment of aqueous solutions contaminated with anionic sulfur dye

The present study assessed the adsorption of an anionic dye (sulfur blue) by methyl-esterified eggshell membrane (MESM), a low-cost and abundant material from waste. Adsorption kinetics were investigated using parameters such as pH, contact time, initial dye concentration, solution temperature, dosage of adsorbent, and particle size of adsorbent. After methyl esterification, the specific surface area significantly increased and the negative surface charge of the eggshell membrane changed to positive for all pH values, which increased the sulfur dye sorption capacity. The optimal conditions for sorption of sulfur dye onto MESM resulted in >98% removal and were as follows: <35 μm particle size, pH 8, 20 min contact time and 313 K temperature. In this respect, 0.68-0.73 dry weight mg/L sulfur dye was adsorbed per 1 mg/L MESM. The Langmuir adsorption capacity for sulfur dye was 187.6 mg/g. In addition, sulfur removal was spontaneous and uptake was endothermic. MESM is an inexpensive and effective adsorbent.