Okra mucilage embedded chitosan@ graphene oxide composite for efficient adsorption of mercuric ions: Kinetic and...

The development of novel adsorbents with superior adsorption performance presents an effective strategy to tackle the growing issue of mercuric ion (Hg²⁺) contamination. This study focuses on the fabrication of three efficient adsorbents: graphene oxide (GO), graphene oxide/chitosan (GCS), and graphene oxide/chitosan reinforced with okra mucilage (OGS). The synthesized adsorbents were characterized using various physicochemical techniques, which confirmed that OGS possessed a surface area of 456.9 m²/g, a pH_PZC of 6.7, and a pore radius of 2.30 nm. The observations were successfully explained utilizing Langmuir adsorption isotherm and the pseudo-second order kinetics. OGS showcased a superior adsorption capability of 538.5 mg/g for Hg²⁺ at 2.0 g/L dose, 25 min of agitation period at 25 °C, and a pH of 5. Following six rounds of adsorption-desorption, roughly 6.0, 5.7, and 2.2 % diminished performance was detected for GO, GCS, and OGS, respectively. Thermodynamic investigations proved that Hg²⁺ ions adsorb spontaneously via an endothermic mechanism. The column adsorption capacity was 305.8 mg/g at a Hg²⁺ concentration of 100 mg/L, with a flow rate of 15 mL/min and a bed height of 2 cm. Both the Yoon-Nelson and Thomas models match significantly with the column adsorption data of Hg²⁺ ions on OGS. Our results demonstrated that OGS exhibits excellent adsorption performance, highlighting its potential for application in water remediation.