Adsorption Characteristics Of Three Phenolic Compounds On Fresh Calcium Phosphate

Phenolic compounds is one of the main factors that deepen the color value in juicewhich are formed by enzymatic and chemical reaction. Adsorption of calcium phosphateplays an important role in juice decolorization on process of clarificating. This papermainly studied on adsorption characteristics of phenolic compounds i.e. gallic acid,chlorogenic acid and vanillin on fresh calcium phosphate. The main research results arereported as follows:1. The kinetic adsorption of phenolic compounds, i.e. gallic acid, chlorogenic acidand vanillin from aqueous and10%sucrose solution on fresh calcium phosphate followedthe pseudo-second-order kinitic. The pseudo second order rate constant k2of phenoliccompounds i.e. gallic acid, chlorogenic acid, vanillin were6.716×10-2,2.694×10-2,1.675×10-2g·mg-1·min-1,1.9802×10-2,0.9767×10-2,0.5219×10-2g·mg-1·min-1and2.6767×10-2,1.3243×10-2,0.8715×10-2g·mg-1·min-1from aqueous solution as the initialconcentration were25,50and75mg·L-1, respectively. Compared with adsorption fromaqueous solution, the adsorption rates of three phenolic compounds on fresh calciumphosphate from sucrose solution were reduced due to the presence of sucrose. The timehas been extended to reach adsorption equilibrium. The pseudo second order rate constantk2of gallic acid, chlorogenic acid and vanillin were6.143×10-2,2.684×10-2,1.490×10-2g·mg-1·min-1,1.5195×10-2,0.8134×10-2,0.4739×10-2g·mg-1·min-1and2.6697×10-2,1.2888×10-2,0.8246×10-2g·mg-1·min-1from10%sucrose solution as the initialconcentration were25,50and75mg·L-1, respectively.2? The change of adsorption capacity of gallic acid, chlorogenic acid and vanillinon fresh calcium phosphate caused by pH from aqueous solution has a same trend withsucrose solution. The adsorption was less effective at pH lower than6, and it increasedrapidly as the pH continue to rise, the greatest adsorption occurred at pH between7.2and7.5. After that adsorption decreased sharply.The regular of adsorption in sucose solution assame as in aqueous solution,while its adsorption capacity was lower than that.3. The adsorption isotherm of phenic compounds i.e. gallic acid, chlorogenic acid andvanillin from aqueous and different concentrations of sucrose solution on fresh calciumphosphate was studied. The results showed that Langmuir isotherm fitted the adsorptiondata quite reasonably. Sucrose concentration had influence on adsorption. Adsorptiondecreased as sucrose concentration increased and the maximum adsorption occurred inaqueous solution. The maximum adsorption capacity of gallic acid, chlorogenic acid andvanillin were8.4317,8.0906,7.7160,7.3964,7.0872,7.0771mg·g-1,15.36,14.60,13.99,13.50,13.00,12.85mg·g-1and7.0373,6.6667,6.3251,6.0606,5.8685,5.8514mg·g-1as sucrose concentrations were0.0%,0.1%,0.5%,1.0%,5.0%and10.0%, respectively.