Enhanced adsorption of deltamethrin by a SiO2 aerogel/chitosan/humic acid composite using co-precipitation method: Characterization and adsorption mechanism

In this study, a SiO 2 aerogel/chitosan/humic acid composite (SA-CS-HA) was synthesized through co-precipitation for efficient removal of deltamethrin (DM) from water, and its potential application in fruit and vegetable juices was explored. SA-CS-HA exhibited a predominantly microporous and mesoporous structure, with its specific surface area of 483.24 m 2 /g, its pore volume of 0.61 cc/g, and its pore diameter of 1.43 nm. The FT-IR analysis revealed that SA-CS-HA contained abundant reactive functional groups, including carboxyl, hydroxyl, and aromatic compounds. And the thermal stability of composite SA-CS-HA was enhanced. The optimal conditions for DM absorption by SA-CS-HA were determined as followers: a temperature of 30 ℃, DM concentration of 20 mg/L, pH of 4, adsorbent dosage of 4 mg, and the adsorption time of 600 min. The kinetics study showed that the adsorption data conform to the pseudo-second-order kinetic model; the Langmuir model suggested that the monolayer adsorption occurred on the surface of SA-CS-HA, with a maximum adsorption capacity of 209.52 mg/g at 30 ℃; the Dubinin-Radushkevich model indicated that adsorption was a physical process; the thermodynamics analysis affirmed the spontaneous nature of adsorption, with its physicochemical properties not affected during application to fruit and vegetable juices. Additionally, the study of the adsorption mechanism of SA-CS-HA highlighted the significant role of electrostatic attraction, accompanied by hydrogen bonding interactions involving oxygen-containing functional groups such as -OH and -COOH in SA-CS-HA.