抄録
The equilibrium isotherms for adsorption of phosphate on an OH-type strongly basic ion exchanger, DIAION SA10A, in both single and binary systems were studied experimentally. The results appeared technically feasible. Phosphoric acid, acetic acid, lactic acid, and pyroglutamic acid were used as adsorbates. Phosphoric acid as well as the other three organic acids has been found to contain mainly in the aqueous-phase component of the sub-critical water hydrolysis of organic wastes. Phosphoric acid is a very important basic material to many industries. However, the worldwide supply of high-grade phosphate rocks is now rapidly decreasing and would likely be depleted in the next few decades. Thus, it is very important to develop a production process of phosphates from various phosphate-utilizing industrial processes, phosphate-containing wastewaters, and from sub-critical water hydrolysis of organic wastes to become alternative sources of phosphates to prevent a global exhaustion of high-grade phosphate ores in the very near future. In all single-component systems, the adsorption isotherms showed a high amount of phosphoric acid, acetic acid, lactic acid, and pyroglutamic acid adsorption and the equilibrium isotherms were not affected by the initial concentrations of the solution. In the three binary systems considered: phosphoric-acetic, phosphoric-lactic, and phosphoric-pyroglutamic acids, it is apparent that phosphoric acid is selectively adsorbed on DIAION SA10A than lactic, acetic, and pyroglutamic acids. The ion-exchange reaction models were then proposed. By applying the mass action law to the dissociation reactions of the adsorbates in the liquid phase and ion-exchange reactions, the theoretical equations for the adsorption isotherms for the single-component systems were derived and the unknown equilibrium constants were determined.
