Adsorption Potentials of Alfisol on Glyphosate and Cadmium Contaminants

Abstract

Aims: This study aimed at demonstrating the adsorption capacity as well as the removal of glyphosate and cadmium unto Alfisols. Place and Duration of Study: Research was carried out in Analytical Laboratory of Department of Chemistry, University of Ibadan, Nigeria. The soil sample was collected from an undisturbed forest land, University of Ibadan, Nigeria. Methodology: The soil sample was air dried for 72 hours under ambient temperature and allowed to pass through 2 mm sieve before use. All solutions and soil dispersions were prepared using de-ionised water. The pH, organic carbon, particle size, exchangeable cations, cation exchange capacity, available phosphorus and soil total nitrogen were all analysed for in the soil sample following the standard procedures likewise the cadmium and glyphosate adsorption/adsorbent studied. Results: The pH of the soil is slightly acidic with high total organic carbon, while the cation exchange capacity is on the lower side. The textural class of the soil greatly influences its water retention capacity, thus the soil under study is predominantly sandy. A decrease in the equilibrium adsorption capacity was observed when the adsorbent dose was increased from 0.2 – 0.8 g however, with a sharp increase at a dose of 1 g. An increase in the percentage cadmium removal was observed with increase in pH from 48.80% to a maximum of 91.10% at neutral pH. The result also indicates that increasing the initial concentration of the cadmium ions and glyphosate lead to an increase in the uptake capacity of the soil for both adsorbate. At higher ionic strength of 0.1 M, the peak removal was obtained at initial concentration of 10 ppm which eventually attains equilibrium at other concentration level. Conclusion: Alfisol can therefore concluded to be an adsorbent provided some conditions like a low cadmium concentration, a neutral pH and a higher adsorbent dosage are adhere too. While glyphosate removal, a pH of 5 and higher ionic strength of KNO3. is required.