Methylene blue, a synthetic dye widely used in various industries, has become one of the major contributors to water pollution. With concentrations often ranging between 10–200 mg/L, wastewater containing methylene blue poses a significant threat to water sources, human health, and ecosystems. When discharged into the environment, this dye not only creates aesthetic issues but can also produce toxic compounds through hazardous chemical reactions. Therefore, effective treatment of this pollution is essential.

To address this issue, various methods have been applied to remove methylene blue from wastewater. Among these methods, adsorption has emerged as one of the most efficient and cost-effective solutions. Researchers Erni Misran, Aqnes Faulina Sihombing, Dina Valianty Sitorus, and Viqry Pramananda (Universitas Sumatera Utara), Muhammad Dani Supardan (Universitas Syah Kuala), and Dewi Agustina Iryani (Universitas Lampung) conducted a study on this phenomenon. Their research found that ultrasonic adsorption is not only easy to implement but also allows the use of locally available materials as adsorbents. One of the key innovations in this study is the utilization of blood cockle shells (Anadara granosa) as a low-cost adsorbent to remove methylene blue with the aid of ultrasonic waves.

Blood cockle shells contain a high percentage of calcium carbonate (CaCO₃), reaching up to 98.7%, making them a highly potential material for the adsorption process. This technique is expected to yield better results compared to conventional methods. "The adsorbent preparation process involves processing blood cockle shells into three different types of adsorbents—A1, A2, and A3—using different treatment methods. Each preparation method affects the morphology and elemental composition of the resulting adsorbent. Characterization was conducted using various techniques such as SEM-EDX and FTIR to ensure the quality and effectiveness of the adsorbent," explained Erni Misran.

Furthermore, this study explored several parameters influencing adsorption efficiency, including solution pH, adsorbent mass, contact time, and initial methylene blue concentration. The results showed that the optimal conditions for methylene blue removal were achieved at pH 12, with an adsorbent mass of 0.5 g and a contact time of 60 minutes. Under these conditions, the removal percentage reached an impressive 98.614%.

Interestingly, the use of ultrasonic waves in this process significantly enhanced removal efficiency by 63.119%, compared to the non-ultrasonic process, which only achieved 35.495%. This finding indicates that ultrasonic technology accelerates mass transfer between liquid and solid phases, thereby increasing adsorption effectiveness.

"Further analysis of the adsorption mechanism revealed that the process follows the Sips isotherm model and pseudo-second-order kinetics," stated Erni. This suggests that electrostatic interactions between the adsorbent surface and methylene blue cations, along with monolayer formation on the heterogeneous surface of the A3 adsorbent, play a crucial role in the adsorption process. Another significant advantage of this study is the reusability of the A3 adsorbent. With outstanding performance, this adsorbent can be reused for up to six cycles without losing its effectiveness.

Blood cockle shells offer a highly effective alternative as an adsorbent for methylene blue removal from wastewater using ultrasonic waves. By utilizing local resources and simple technology, innovative solutions can be developed to address the pressing issue of water pollution in the modern era. Further research is expected to expand the application of blood cockle shells in treating other wastewater contaminants and enhance our understanding of the fundamental mechanisms underlying the adsorption process.

Concrete steps toward better wastewater management can be taken through science- and technology-based approaches that are environmentally friendly. "Such efforts will not only help maintain the cleanliness of our water sources but also protect public health and ensure the sustainability of ecosystems as a whole," concluded Erni.