Adsorption Reaction and Kinetics of Zn on Zeolite Mineral Compared with Two Calcareous Soil

Abstract

A laboratory experiment was conducted to study the adsorption of zinc element in eight concentrations (0, 25, 50, 100, 150, 200, 250 and 300 mg L-1) from its source ZnSO4.7H2O. Two repetitions were performed for each concentration, where 20 mL of zinc solution was added to 1 gram of natural zeolite, synthetic zeolite, soil 1, and soil 2. The Langmuir equation was used to describe the relationship between the adsorbed zinc and its concentration. Additionally, the Freundlich equation was used to describe the adsorption of ions. The Freundlich equation was found to be more important than the Langmuir equation, as the values of k and b in the Freundlich equation and the R2 values for natural and synthetic zeolites were higher in both soils. The second experiment involved kinetics. Samples of natural zeolite, synthetic zeolite, soil 1, and soil 2 were taken, weighing 40 grams, to which zinc with a concentration of (100, 1000 mgL-1) prepared from ZnSO4.7H2O was added. They were placed in plastic containers for periods of (0, 1, 5, 10, 20, 30, 40, 60 and 80 days). The zeolite and soil were kept moist at field capacity throughout the incubation period. Zinc was extracted using DTPA after each incubation period, with two replications, to study the rate of zinc release from zeolite and soil over time and its concentration in the solution. The results showed a decrease in the availability of added zinc with increasing incubation time. The highest concentration of available zinc was found when zinc was added to synthetic zeolite, reaching 346 micrograms Zn+2ml-1 at the end of the incubation period. The second-order equation was the most effective in describing the behavior of zinc and its reaction rate during the incubation period, representing the period of crop growth.