The role of lime juice in improving the performance of basic sites on activated carbon surfaces in sulfate ion adsorption in seawater

Abstract

The aim of this research was to investigate the utilization of lime juice in enhancing the performance of commercially produced activated carbon from coconut shells for decreasing the sulfate ion content in seawater. Seawater, which serves as the raw material for sea salt production, contains relatively high levels of sulfate ions as impurities. The removal of sulfate ions from seawater is essential in minimizing impurities during the crystallization process of sea salt. The study employed two types of activated carbon: activated carbon without further treatment (ACB) and acid-washed activated carbon (ACA). The objective was to explore the mechanism of sulfate ion adsorption when lime juice was introduced to the seawater. Various concentrations of lime juice were used in the adsorption experiment, based on the optimum dosages and time determined in the preliminary study. The results indicated that ACB exhibited a higher sulfate ion adsorption capacity (320 mg SO42− g−1) compared to ACA (298 mg SO42− g−1). The addition of lime juice led to a decrease in solution pH and an increase in sulfate ion adsorption. This suggests that lime juice enhanced the capacity of basic sites present in the activated carbon. The proposed model for sulfate ion adsorption posits that the ions are attracted to the functional groups and subsequently to the basic sites in the carbon basal planes, mediated by hydronium ions.

Keywords

• Sulfate
• Seawater
• Lime juice
• Activated carbon
• Basic functionalities