In-depth analysis of MgAl layered double oxide AC composite for sulfate removal from United Arab Emirates Ground Water: Synthesis optimization, fixed-bed performance, and economic feasibility

Abstract

Excessive sulfate (SO42−) concentrations in groundwater pose health and environmental risks that require effective treatment strategies. This study focuses on optimizing the synthesis conditions of activated carbon doped MgAl layered double oxide (MgAl LDO/AC) and addresses the treatment of SO42− contamination in United Arab Emirates (UAE) groundwater. The study delves into key parameters such as the Mg/Al molar ratio and calcination temperature, unveiling optimal adsorption performance at a 3:1 M ratio and 500 ℃ calcination. The optimized MgAl LDO/AC(3:1/500 ℃) demonstrated notable selectivity for SO42− in the presence of NO3–, while exhibiting competition with H2PO4−, CO32−, HCO3−, and Cl−. In fixed-bed column studies, optimal performance was achieved with a lower influent concentration (50 mg/L), longer bed height (10 cm), and reduced flow rate (5 mL/min), resulting in a prolonged saturation time of 31.7 h, adsorption capacity of 429.5 mg/g, reduced axial dispersion coefficient, and enhanced mass transfer process. The real groundwater treatment demonstrated the composite's efficiency in reducing SO42− from 2606.6 to 817.5 mg/L, with additional removal of Cl− and NO3− ions, emphasizing its potential as an efficient pretreatment stage for highly contaminated and saline groundwater. Material characterization revealed the dominance of the chemical adsorption process of SO42− including surface complexation and ion exchange. Economic feasibility evaluation underscored the practicality of the composite, indicating its potential application in real plants with a cost below 20 US$/kg. Overall, MgAl LDO/AC(3:1/500℃) stands as a promising and cost-effective solution for removing SO42− in real-world water treatment scenarios, especially in regions facing water challenges.