Study upon kinetic process of apple juice adsorption de-coloration by using adsorbent resin

This paper deals with the effects of adsorbent resin upon kinetic process of apple juice adsorption de-coloration in the case of different temperatures (25–70 °C) and different resin concentrations (1, 2, 8 g/L). The testing results indicate that the resin adsorption equilibrium curve is found to be in coincidence with Langmuir and Freundlich models and model parameter values (Kad, Q0, Kf, and n) are obtained under the conditions of different temperatures. The variation in adsorption enthalpy values (ΔH) is 4.16 kJ/mol, indicating that this process is a heat adsorption process. Free energy (ΔG) appears to have the declined tendency with an increase in temperature, whereby showing that this process is a spontaneous process. The kinetic parameters of apple juice adsorbent de-coloration under the different resin concentrations and different temperatures are further calculated with testing data. With an increase in temperature, the adsorption ability is increased, but there is a reduction in the initial balancing time. Within the range of 2–4 g/L resin concentration, the adsorption effect is rather apparent; and at the temperature of 55 °C, the initial coverage rate (θe) which resin reaches to initial equilibrium can be higher, on the basis of which the determination of optimal temperature and resin concentration ranges of the effect of resin upon apple juice adsorption de-coloration can be 55 °C and 2–4 g/L.