Effect of Incorporation of Pectin on the Adsorption of Phosphate by Al (oxy)hydroxides

摘要

The structural and surface charge properties of Al (oxy)hydroxides formed in the presence of pectin, as well as the effect of incorporating pectin on phosphate adsorption by Al (oxy)hydroxides, are examined in this study. Results indicate that pectin entered the structure of the Al (oxy)hydroxides during their formation, which inhibited crystallization of Al hydrolysis products. The incorporation of pectin decreased the surface positive charge on the Al (oxy)hydroxides and the point of zero charge of hydroxides. The amount of phosphate adsorbed by Al hydrolysis products incorporating pectin was considerably higher than that adsorbed on products without pectin at the same pH within the range 4.5-6.0. The maximum adsorption capacity of phosphate on Al (oxy)hydroxides increased from 134.7 mmol kg(-1) for that formed without pectin to 248.2 mmol kg(-1) for that formed by incorporation of pectin at an initial pectin/Al loading ratio of 20 mg mmol(-1). Adsorption kinetics indicated that the incorporation of pectin decreased the rate constant and increased the maximum adsorption capacity of phosphate on the surface of Al (oxy)hydroxides. In conclusion, incorporation of pectin affects the surface properties of Al (oxy)hydroxides and leads to an increase in adsorption of phosphate.