The ion-exchange properties of amorphous aluminum phosphate have been studied in aqueous electrolyte solutions of KCl over a temperature range of 300-320 K. The data were explained by the law of mass action. Sorption of Cu2+, Ni2+ and Co2+ on AlPO4 was also studied as a function of temperature and concentration, and the data were fitted to Langmuir adsorption equations. In all cases the adsorption was found to increase with increases in temperature and concentration in the selectivity order Cu2+ > Co2+ > Ni2+. Further, the values of Langmuir constants were used to calculate the thermodynamic parameters Delta S degrees, Delta H degrees, and Delta G degrees.