Synergistic Adsorptive Removal of Urea from Agricultural Effluents Using Ball Clay and Sepiolite Composite

Abstract

Agriculture effluents have become a big problem since water is the basic component of all operation in agriculture practice. These effluents composed of agrochemicals such as fertilizer, pesticides, herbicides, crop residues are the pollutants of agricultural effluents. Lakes, rivers and streams often receives water run-off from farmlands. Nitrates and urea in the water bodies are toxic to aquatic lives by causing depletion of oxygen in water making it unfit for human and aquatic life. This research assessed the adsorptive removal of urea from agricultural effluent by means of thermally activated ball clay and sepiolite composite (TABCSC) and non-activated ball clay and sepiolite composite (NABCSC) as absorbent. The adsorption process was done at Varying amounts TABCSC (0.6g - 4.5g), pH range of 3 - 11, time (30 - 90 minutes) and temperature (25 – 45°C) as recommended by design expert version 13. TABCSC and NABCSC characterized by means of Fourier transformed infrared spectroscopy (FTIR) and scanning electron microscope (SEM) reveals the presence of large surface area, porosity as well as the functional groups: hydroxyl, carboxylic, hydrogen bonding and aldehyde group that aids adsorptive removal of urea. The highest adsorptive removal efficiency by TABCSC was found to be 99.23% (at pH = 7, temperature = 25°C, dosage = 0.6 g and time = 60 minutes) while that of NABCSC was at 93.23% (at pH = 11, temperature = 35°C, dosage = 0.6 g and time = 60 minutes). The adsorptive removal of urea was found to increase with increase in pH value and contact time. The adsorptive removal mechanism of Urea by TABCSC was more fitting to the second order kinetics (R2 = 0.9770) while removal by NABCSC aligns with the pseudo first order kinetics (R2 = 0.9770). The isotherm of the removal process conforms more to the Freundlich isotherm of TABCSC (R2 = 0.9995) and NABCSC (R2 = 0.9671) respectively.