Comparative study of fly ash derived adsorbents, synthesis and application

Emerging contaminants (ECs) like tetracycline (TC) pose severe risks to the environment and public health. Adsorption has gained prominence as an effective method for removing tetracycline due to its simplicity, cost-effectiveness, and ability to achieve high removal efficiencies. Fly ash is a hazardous byproduct of coal combustion, often discarded in landfills, posing environmental risks. However, it can be repurposed into low-cost adsorbents. This study aimed to develop and evaluate various fly ash (FA)-derived adsorbents for TC removal, leveraging waste materials for environmental sustainability. Several adsorbents were derived from FA, including, acid-modified FA (AM-FA), base-modified FA (BM-FA). and zeolite Na-P1 (ZNa-P1). Furthermore, silica nanoparticles (SiNPs) were derived from FA (FA-SiNPs) and subsequently FA-SiNPs was doped with iron to create Fe-SiNPs. Note that FA, AM-FA, BM-FA, and ZNa-P1 were tested separately to the silica nanoparticles-based adsorbents. The comparative adsorption test among FA, AM-FA, BM-FA and ZNa-P1, ZNa-P1 removed the most TC, at 90 % removal. Optimal TC removal with ZNa-P1 was achieved at 7.5 g/L dosage and pH 5. The adsorption of TC on ZNa-P1 followed pseudo-second-order kinetics and the Langmuir isotherm model, with a maximum capacity of 46.34 mg/g at 30 <b>°</b>C. The comparative adsorption tests among FA-SiNPs, SSSNPs, and Fe-SiNPs revealed that Fe-SiNPs demonstrated superior performance, removing 59 % of tetracycline. Optimal TC removal using Fe-SiNPs was achieved at a dosage of 5 g/L and within a pH range of 4-5. The adsorption of TC on Fe-SiNPs followed Elovich kinetics and the Langmuir isotherm model, with a maximum capacity of 32.31 mg/g at 30 <b>°</b>C. This study highlights the potential of FA-derived adsorbents, particularly ZNa-P1 and Fe-SiNPs, as sustainable solutions for removing TC from contaminated water. The findings contribute to advancing waste utilization strategies, particularly adsorption, for environmental remediation.