Effect of organic compounds on phosphate sorption-desorption of some pure minerals [electronic resource].

Includes references.

Phosphorus sorption-desorption in some pure systems, i.e., goethite, kaolinite, and bentonite had been studied under different concentrations of phosphorus, pH values, constant time, wide solid: solution ratio. The effect of oxalate (OX) and or humic acid (HA), and the order of their addition on phosphorus sorption-desorption was also investgated. The obtained P-adsorption isotherms for the tested minerals were of the high affinity type with maximum P-adsorption (b) in the order: goethite > kaolinite>bentonite. Adsorption energy of P on goethite surfaces was greater than that of clay surfaces. Amounts of P sorption on goethite and clay minerals decreased with increasing pll. Presence of OX and EA, of all systems, had no effect on P sorption by goethite or clay minerals under low P concentration. On the other hand, in the system with high P concentration organic acids reduced P sorption by goethite or clay minerals. The reduction on P sorption was dependent on the order of anions addition and pH value of the system. Organic acids drastically reduced P sorption either when added with P or especially when introduced before P. The higher the pH was, the lower the efficiency of organic acids in reducing P sorption was. Amounts of desorbed P from goethite and clay minerals increased as the initial P concentration increased in all orders of addition. Percentages of des orbed P from goethite decreased as pH value increased from 5.5 to 7.5. On the other hand, percentages of desorbed P from clay minerals decreased as pH value was raised from 5.5 to 6.5 whereas raising pH to 7.5 resulted in an increase in the percentages of desorbed P for all treatments. Greater amounts of desorbed P have been recorded for the (P/OX) and (P/HA) orders of addition. Keywords: Organic compound, Phosphate sorption-desorption.

Summary in Arabic.

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