Adsorptive Removal of Phosphate from Agricultural Effluent using Thermally and Non-Thermally Activated Sepiolite Clay

Abstract

This study assessed the use of thermally activated sepiolite clay (TASC) and non-activated sepiolite clay (NASC) as adsorbents for phosphate adsorption from agricultural effluent. The effect of pH, temperature, dosage, and time on the adsorbates was investigated at pH 4-11, temperature 298 - 318k, contact time 30 – 120 minutes, and adsorbent dosage 0.2 - 4 g in 100 mL of agricultural effluent. Fourier-transformed infrared spectroscopy (FTIR) and Scanning electron microscope (SEM) techniques were used to determine adsorbent features. TASC and NASC exhibit an excellent capacity for adsorbing phosphate molecules. At equilibrium, the removal efficiency of phosphate at 4 different varying conditions of temperature, pH, adsorbent dosage, and time gave more than 100 % for TASC, while NASC also recorded over 100% adsorption of phosphate at 3 different varying conditions. The amount of phosphate adsorbed was found to decrease with an increase in temperature and contact time. The isotherm adsorption data fitted the Langmuir better than the Freundlich model, where the correlation coefficients of Langmuir and Freundlich were 0.9994 and 0.8901, respectively. The adsorption kinetics was better explained by the pseudo-first-order kinetic model with R2 values TASC (0.9999) and NASC (0.9999) than the second order with R2 value TASC (0.9984) and NASC (0.9820).