Molecularly Imprinted Polymers Based on Konjac for Selective Caffeine Adsorption in Aqueous Solution

Abstract

A number of caffeine extraction methods have been developed, such as microwave assisted extraction and ultrasonic-assisted extraction. The disadvantages of these methods are low selectivity, inconvenience, and inefficiency. Among the existing technologies, molecularly imprinted polymers (MIPs) are one of the most efficient and economical methods for the removal of caffeine contaminants. In this study, the objective was to prepare MIPs for the removal of complicated samples. The obtained materials were used as a sorbent for the extraction of caffeine from coffee brewed in an espresso. The MIPs were prepared using konjac/acrylic acid as a functional monomer, N, N′-methylenebisacrylamide as a cross-linker, and caffeine as a template. The chemical structures of MIPs were characterized by Fourier transform infrared spectroscopy. MIPs exhibited a higher maximum adsorption capacity (87.72 mg/g). The equilibrium adsorption data fit well with the Langmuir adsorption isotherm models, which confirm the monolayer adsorption behaviour of caffeine molecules on the surfaces of the MIPs samples. According to the experimental results of the adsorption capacity of caffeine from aqueous solution, the MIPs showed a higher percentage removal of caffeine (75.66%). Our findings suggest that MIPs are useful adsorbents for the decaffeination of coffee brewed in an espresso.