Kinetics of Phosphorus Adsorption in The Calcareous Soils of Kurdistan Region, Iraqi

Abstract

Phosphorus is the second macronutrient which is vital for plants normal growth. In the calcareous soils, the adsorption is the main process that controls P availability to plants. This paper reviews the P adsorption phenomenon in the calcareous soils of Iraqi Kurdistan. In this study, the P adsorption capacity of the selected soils was determined by adding 10 mL of 0, 50, 100, and 200 mg P L-1 as (KH2PO4) to 1.0 g of soil and shaken for 12, 24 and 48 hours on horizontal shaker constantly. The suspensions at each period of incubation centrifuged and filtered then 1nalysed for P which represented the equilibrium P concentration. The minimum adsorption 4.42±0.44 mg kg-1 was recorded for soil4 with 50 mg P L-1 applied solution and 12 h of incubation while the maximum adsorption 124±0.05 mg Kg-1 was recorded for soil3 with 200 mg P L-1 applied solution at 48 h of incubation. These results indicate that P adsorption increased with increasing applied amount of P and time of incubation. Results also showed that the Freundlich model was the best fitted according to the greater values of R2 which was ranged from 0.7619 to 0.9984 compared to 0.738-0.9882 for Langmuir model and 0.7171-0.9986 for Temkin model. These results also suggest that in the studied soils P adsorbed through physical adsorption rather than chemical reaction and then decrease P availability in soil.

Enhancement of Phosphorus Sorption onto Peanut shell by Means of Aluminum and Iron Oxide Coatings

“…This reduction in the affirmative charge present on the surface of the particles leads to a diminished electrostatic interaction between the adsorbent and the adsorbate. This observation aligns with the findings of Tariq, et al 2021 [21], who examined the rate at which phosphorus is adsorbed in calcareous soils. In addition, the OH-ions in the solution are increased.…”

“…Adsorption of P on Peanut shells rather than Al-coated and Fe-coated particles was investigated. The persistent adsorption of P over time is expected to result in a significant alteration in the adsorption isotherm [21]. Both Freundlich's equation (1) (Figure 1) and Langmuir's equation (2) (Figure 2) were successfully fitted to the experimental data with a coefficient of determination (R2) greater than 0.96.…”

“…A study was carried out to investigate the absorption of phosphorus (P) in peanut shells under laboratory conditions. The experiment involved three replicates from each of the three peanut shells, and a time-dependent adsorption isotherm method was employed, as detailed in reference [21]. Dried specimens (1 g, 2 mm) were introduced into distinct 50 mL containers for centrifugation that had been cleansed with acid.…”

“…The mathematical expressions for the two aforementioned models are provided in equations [3] and [4]. The models for adsorption isotherms can be employed to establish the partitioning of P between the solid and liquid phases, utilizing a linear function as suggested by Tariq, et, al [21]. In this particular investigation, the Freundlich and Langmuir adsorption isotherm models, which are widely employed, were utilized in their linear formats to explore the adsorption of P in the samples under examination.…”

“…In the present investigation, the KL values varied from 0.03 mg l -1 for Fe-coated, 0.06 for peanut shell, to 0.27 for Al-coated particles as shown in table 3 and figure 2, which implies the advantageous circumstances for the adsorption of P through the utilization of peanut shell. A positive K-value indicates the spontaneity of the adsorption reaction at ambient temperature, while KL's significance indicates the extent of this spontaneous adsorption reaction [21]. The increased K-value corresponds to a higher degree of spontaneity and greater stability of the products, resulting in an increased retention of P [26].…”