Adsorption kinetics, thermodynamics, and equilibrium of alpha-toluic acid onto calcium peroxide nanoparticles

摘要

The present work addresses the kinetics, thermodynamics, and equilibrium of alpha-toluic acid adsorption onto calcium peroxide (CaO2) nanoparticles. CaO2 nanoparticles were synthesized by chemical precipitation method and characterized using XRD, TEM, and FT-IR. Characterization results confirmed that CaO2 nanoparticles were in the size range of 5-15 nm. The rate of alpha-toluic acid adsorption was determined by fitting the batch adsorption experimental data with pseudo first order, pseudo second order, Elovich, intra-particle diffusion, fractional power, and Bangham kinetic models. Amongst all models, the pseudo second order model showed good correlation with a rate constant, k(2) = 8.53 x 10(-5) g mg(-1) min(-1). Thermodynamic parameters (Delta G degrees, Delta N degrees, and Delta S degrees) showed that adsorption is more favorable at low temperature, and an exothermic process. The equilibrium data were analyzed with Langmuir, Freundlich, Temkin, Toth, and Radke-Prausnitz isotherms, and the best fit was observed with Langmuir isotherm suggesting monolayer and chemisorption of alpha-toluic acid. This was also confirmed from error analysis. On quantitative basis, the adsorption capacity of CaO2 nanoparticle adsorbent was found to be around 30% higher as compared to the conventional CaO2. Based on FT-IR analysis, a mechanism for alpha-toluic acid removal from aqueous solution using CaO2 nanoparticles was proposed. (C) 2016 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.