Synergistic Study of Hydroxyiron (III) and Kaolinite Composite for the Adsorptive Removal of Phenol and Cadmium

This research used raw kaolinite (RK), thermally activated Kaolinite (TAK), hydroxyiron (iii) kaolinite- composite (HKC), as adsorbent for the adsorption of phenol and cadmium from aqueous solutions over a concentration range of 5–25 mg/l and 10-50 mg/l respectively. Effect of initial pH on the adsorbates was carried out at pH 2-11 at (298 K), and adsorbent dosage from 0.5 - 2.5 g with 50 ml adsorbate solution. Adsorption thermodynamics were developed for 25-55°C for 5-25 mg/L and 10-50 mg/L of phenol and cadmium solutions for 1 hr for all the adsorbents. The Physicochemical characteristics of RK, TAK and HKC were shown to be: pH 7.38, 7.26 and 7.20; pHzpc: 11.00, 10.50 and 10.10; Conductivity (2μ/cm):1.656, 1.660 and 1.657; Bulky density (g/cm3):1.186, 1.111 and 1.214; Attrition (%): 17.49, 26.53 and 27.21 respectively. X-ray fluorescence (XRF), Fourier transformed infrared spectroscopy (FTIR) and Scanning electron microscope (SEM) techniques were used to determine adsorbent features. The presence of hydroxyl, carboxylic, hydrogen bonding and aldehyde group showed that adsorbents bonds phenol and cadmium. At equilibrium, the maximum percentage removal for phenol: RK (52.020%), TAK (63.468%), HKC (79.952%) and cadmium: RK (41.980%), TAK (48.398%), HKC (65.830%) respectively were achieved for contact time. From the experiment adsorption capacities were found to increase with increase in temperature, contact time and concentration. The equilibrium adsorption data fitted the Langmuir better than the Freundlich model. The calculated thermodynamic parameters –Enthalpy change entropy change and Gibbs free energy, adsorption of both phenol and cadmium was not spontaneous but endothermic, meaning the chemisorption dominates physosorption. Adsorption kinetics was better explained by the Blanchard pseudo-second order kinetic model than the Lagergren first order. Overall, the adsorption of phenol was more favourable than for cadmium for all adsorbents