Case Studies in Chemical and Environmental Engineering (Dec 2024)
Utilizing banana peel-derived graphene oxide nanosheets for adsorptive removal of pharmaceuticals from wastewater
Abstract
The research investigated the adsorption capacity of graphene oxide nanosheets towards non-steroidal anti-inflammatory drugs (NSAIDs) across diverse experimental conditions. Batch adsorption experiments indicated a correlation between higher pH levels, elevated temperatures, and increased adsorption capacity, affirming theoretical expectations. Kinetic analysis revealed pseudo-second-order kinetics predominance, suggesting chemisorption as the rate-limiting step. Moreover, the rate constant (k1) declined with rising pH and temperature, implying a potential impact on reaction kinetics and optimization strategies. For instance, at pH 7 and 30 °C for 4 hours, the adsorption capacity was higher than expected compared to conditions at pH 6 and 25 °C for 2 hours, despite the lower initial concentration of the target substance. The pseudo-second-order kinetics model illuminated the nuanced relationship between pH, temperature, and adsorption rate, emphasizing environmental sensitivity and surface chemistry alterations. Equilibrium adsorption studies employing Langmuir and Freundlich isotherm models underscored monolayer adsorption and revealed varying adsorption capacities and affinities under different conditions. For example, at pH 6 and 25 °C for 2 hours, the maximum adsorption capacity (qmax) was found to be 24.9 mg/g ± 4.2, with a Langmuir adsorption constant (KL) of 0.058 L/mg ± 0.011. The diffusion behaviour within adsorbent particles, assessed via the intra-particle diffusion model, indicated both rapid and progressively slower diffusion with increasing pH and temperature. The findings collectively underscore the complexity of adsorption dynamics, urging comprehensive consideration of pH, temperature, and intra-particle diffusion for optimizing adsorption processes. This research enhances the understanding of graphene oxide nanosheets' adsorption behaviour towards NSAIDs, offering valuable insights for environmental remediation and optimization strategies.
