Isotherm and kinetic adsorption analysis of molecularly imprinted polymers as a selective material for formalin adsorption
Meyliana Wulandari, Syabina Khaila Aliffa, Andreas, Nofrizal Nofrizal, Budi Arifin, Ria Sri Rahayu, Pandian Bothi Raja

1 Department of Chemistry, Faculty of Mathematics and Natural Science, Universitas Negeri Jakarta, 13220, Indonesia
2 Department of Chemistry, Faculty of Science and Technology, State Islamic University (UIN) Syarif Hidyatullah Jakarta, Ciputat, Banten 15412, Indonesia
3 Badan Riset dan Inovasi Nasional, South Tangerang, Indonesia, 15314, Indonesia
4 Ministry of Energy and Mineral Resources - Lemigas, Jl. Ciledug Raya Kavling. 109, Jakarta 12230, Indonesia
5 Department of Chemistry, Faculty of Mathematics and Natural Sciences, IPB University, 16680 Indonesia
6Analytical Chemistry Research Group, Institut Teknologi Bandung, Jl. Ganesha 10, Bandung 40132, Indonesia
7 School of Chemical Sciences, Universiti Sains Malaysia, Minden, 11800, Penang, Malaysia

Abstract

Isotherm and kinetic studies establish the mathematical and physical basis for assessing a material^s maximum adsorption capacity and adsorption rate, which are critical determinants of sensor sensitivity and real-time response. The present study examines the isotherm and kinetic sorption behavior of molecularly imprinted polymers (MIPs) designed for the detection of formaldehyde. MIPs were synthesized from silica, formalin, acrylamide, acetonitrile, azobisisobutyronitrile (AIBN), and ethylene glycol dimethacrylate (EGDMA). Adsorption experiments used formalin concentrations ranging from 0 to 50 ppm and contact times from 0 to 180 minutes. Kinetic modeling included zero-, first-, second-, pseudo-first-, and pseudo-second-order models. Measurements were made using a UV-Vis spectrophotometer at 549 nm. Results demonstrate that formalin adsorption onto MIPs conforms to the pseudo-second-order model (R2 = 0.9496- K2 = 0.5751), indicating that the adsorption rate depends on formalin concentration and likely involves chemical interactions. Isotherm analysis reveals that the Freundlich model (R2 = 0.9902) provides a better fit than the Langmuir model (R2 = 0.7184). This outcome suggests that formalin adsorption occurs on a heterogeneous surface with monolayer coverage, involving both specific imprinted and non-specific sites formed during polymerization. The Freundlich constant (KF) was calculated as 0.3368 mg/g, reflecting the material^s adsorption capacity. Although MIPs display relatively low adsorption capacity for formalin, they offer selective adsorption at both specific and non-specific sites.

Keywords: isotherm adsorption, kinetic adsorption, molecularly imprinted polymers

Topic: Material Physics