Ultrasonic assisted adsorption of methylene blue using blood clam shell as a low-cost adsorbent

Methylene blue is a synthetic dye used in various industries, such as wood, linen, and silk. Generally, as much as 10–200 mg/L of methylene blue is released into the environment and potentially polluting the environment. One of methylene blue removal method from wastewater is adsorption, particularly using blood clam (Anadara granosa) shells adsorbent. Blood clam shells contain CaCO3 (up to 98.7 %) that can be utilized to adsorb methylene. Furthermore, methylene blue adsorption can be enhanced by employed the ultrasonic wave. This research aims to prepare, characterize, and employ blood clam shells as a low-cost adsorbent in the ultrasonic-assisted methylene blue adsorption. The parameters studied were the adsorbent preparation method, adsorbate pH, adsorbent mass, contact time, and initial concentration. The adsorbent preparation method affected the morphology, elemental composition, functional groups, and average particle size, which were confirmed using SEM-EDX, FTIR, and PSA, where this kind of investigation has never been conducted before. Optimum conditions for methylene blue adsorption were obtained for adsorbent A3, pH 12, adsorbent mass of 0.5 g, contact time of 60 min, and initial concentration of 10 ppm, with a removal percentage of 98.614 %. This removal percentage increased by 63.119 % (espescially in A3) compared to without ultrasonic waves, which could only remove methylene blue by 35.495 %. Ultrasonic-assisted adsorption of methylene blue using blood clam shells adsorbent proceeded according to the Sips isotherm model (R2 = 0.9953) and pseudo-second-order kinetics (R2 = 0.939). A3 shows an extraordinary performance, with reusability up to six cylces. The adsorption occurs by electrostatic interaction between adsorbent's surface and cations in methylene blue, chemisorption, and the formation of monolayer adsorbate in heterogenous A3's surface.