Abstract

Aim: This study was aimed to carry out the adsorption kinetics of MCPA on a rice crop soil, as a function of time, and to determine the influence of temperature on it by the pseudo-first and pseudo-second order models.

Method and Materials: The samples were collected in the winter of 2016 at different depths to differentiate the horizons affected by the work of the soil or for the installation of a permanent cover of vegetables used in direct seeding technique. Samples were 0-8 cm deep and the soil used in the study were brown in color (Munsell system), hydromorphic silty loam texture, 22% clay, 46% silt and 32% sand, the most important thing was high content of organic matter (OM) . The adsorbate used in this study was MCPA from Sigma-Aldrich; solutions were prepared using deionized water at three temperatures 25 ° C, 35 ° C and 45 ° C.

Results: The kinetic studies were carried out following the equilibrium technique in batch for 24 hours. A 1g soil sample was contacted with 30 mL of a 1 mg L^-1 MCPA solution in CaCl₂ and a follow-up was carried out taking data at 1-hour intervals during the 24 h. The adsorption capacity (q_e) of MCPA was determined by the correlation: q_e = V (C_i-C_e) / m, where C_i was initial concentration of MCPA (mg L^-1), C_e was its concentration at equilibrium (mg L^-1), V was volume of solution in liters, m was mass of adsorbent expressed in grams and q_e was adsorption capacity (mg g^-1). The remaining MCPA concentration was determined by HPLC.

Conclusion: It was concluded that the experimental kinetic data have a higher correlation with the pseudo-second order model. Intraparticle diffusion was also studied to see if this is the rate-limiting mechanism.

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