Removal of Mn and Cu Ions in Synthetic Wastewater Using Dried Cockle Shell

Abstract

The potential of the dried cockle shell had been studied using an adsorption experiment to determine the effectiveness of Mn and Cu removal from wastewater. A continuous batch adsorption study was carried out to determine the optimum dosage with a range of 3 g to 24 g of dried cockle shell and contact time from 15 minutes to 150 minutes. The equilibrium data for adsorption were analysed by three isotherm models (i.e., Langmuir, Freundlich, Temkin) and three kinetic models (i.e., Pseudo-First Order, Pseudo-Second Order, Elovich) to define the best correlation for each metal adsorption. The result shows that the highest percentage removal of Mn and Cu using dried cockle shells were 77.8% and 88.9%, respectively, with an optimum dosage of 15 g and 105 minutes of optimum contact time. Among these three isotherm models, the Temkin model fitted with the equilibrium isotherm for Cu with the value of r² of 0.963, while the Langmuir model best described the experimental data for Mn with a recorded value of r² of 0.953. From the result, the cockle shell has the ability to adsorb heavy metals such as Mn by the process of a monolayer on the outer layer of the adsorbent and Cu with a Gaussian energy distribution onto a heterogeneous surface. Kinetic studies have shown that the adsorption of Cu and Mn towards the cockle shell follows Pseudo-Second Order with the determination of coefficients of 1 and 0.997, respectively. The findings from characterisation analysis found that a high percentage of CaCO₃ with 95.47% influences the adsorption of Mn and Cu from wastewater. The SEM image of dried cockle shell exhibits needle-like aragonite morphology and cubic-like calcite. Cockle shells have a great potential for removing Mn and Cu from industrial effluent. Thus, it can be used as a filter material and helps increase the economy at a modest pace by recycling low-cost waste for wastewater treatment.