Publication: Synthesis of molecularly imprinted polymer-ordered mesoporous silica adsorbent for batch and fixed-bed column adsorption of chloramphenicol
No Thumbnail Available
Date
2024-09-01
Authors
Zulkarnain Bin Mohamed Idris
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
This study describes a novel synthesis of a surface-imprinted polymer-ordered mesoporous silica adsorbent for highly selective chloramphenicol (CAP) adsorption using activator regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP). Initially, ordered mesoporous silica was synthesized by the sol-gel method and functionalized to prepare a silica-ATRP initiator (SiO2@Br) for polymer grafting. CAP was used as the template molecule for imprinting via precipitation polymerization. The effects of varying polymerization reaction parameters, such as template to functional monomer molar ratio (1:2 – 1:10), template to cross-linker molar ratio (1:4 – 1:20), solvent types (acetonitrile and toluene) and their mixtures (0 – 100%), catalyst to ligand ratio (1:2 – 1:10), catalyst to reducing agent ratio (1:2 – 1:10), reaction temperature (313 – 353 K), and reaction time (6 – 30 h) on imprinting factor (IF) values and adsorption capacities (Qt) were studied. The physical and chemical properties of the resulting adsorbent were analyzed using FTIR, TGA, EDX, SEM, HRTEM, and nitrogen sorption techniques. The SiO2@Br had a specific surface area of 638.31 m².g-1 and a total pore volume of 0.4152 cm³.g-1. Post-polymerization, the specific surface area and pore volume of the adsorbent (SiO2@MIPs-CAPcr) decreased to 11.91 m².g-1 and 0.019 cm³.g-1, indicating successful grafting. Adsorption performance was investigated through batch and fixed-bed column studies. Batch experiments investigated the effects of initial solute concentration (10 – 50 mg.L-1), adsorbent dosage (5 – 25 mg), temperature (293 – 313 K), and initial pH (3 – 11) on CAP adsorption. The adsorption equilibrium data for SiO2@MIPs-CAPcr were well fitted by the Sips models, with a maximum adsorption capacity (Qs) of 19.68 mg.g-1. The adsorption kinetic followed pseudo second-order behaviour. Thermodynamic analysis indicated an exothermic process with entropy change due to reduced molecule movement. Selectivity studies involved antibiotics ciprofloxacin (CIP) and thiamphenicol (TAP) as model adsorbates. Fixed-bed column experiments tested initial concentrations (10 – 50 mg.L-1), volumetric inlet flow rates (0.1 – 0.5 mL.min-1), and bed heights (0.5 – 1.0 cm). The Thomas model best described the fixed-bed column adsorption behaviour. The SiO2@MIPs-CAPcr adsorbent demonstrated remarkable selectivity for CAP and excellent adsorption capabilities in both batch and fixed-bed operations.