Effects of Zeolite Amendment on Soil Phosphorus

The study consisted of two experiments: 1) phosphorus (P) sorption on zeolite using a batch method; and 2) Zeolite was amended in columns containing one of three south Florida soils. Phosphorus sorption on zeolite was described with Langmuir isotherm equations. The P sorption maximum ranged from 29 to 82 mg P kg-1, slight higher than the sandy soil of study. The Langmuir sorption energy for zeolite products ranged from 0.40 to 2.97. Zeolite sorption for P can be manipulated by different treatment to its external surface property. Three times washing with 1N HCl caused an 81.7% decrease in sorption maximum on ZEO1 zeolite. In contrast, the formation of a HDTMA bi-layer membrane around ZEO1 increased its sorption maximum by more than three fold while the sorption maximum for iron-oxide coated ZEO1 was 123.4 times of that for uncoated ZEO1. Phosphorus sorption by zeolite was an initial rapid process, followed by a slow sorption stage that persisted over time. About 87.4% of P sorption on ZEO1 was completed within the first 312 hr. The reaction was best described by a Langmuir kinetic model (r2 = 0.998). P sorption on ZEO1 was a pH dependent reaction and maximum P sorption peaked at pH 5 to 7.