SEQUESTRATION OF PHENOL AND 4-NITROPHENOL FROM AQUEOUS SOLUTIONS USING COCONUT (Cocos nucifera L.) SHELL-CLAY COMPOSITE

Abstract

Pollution is one of the problems that influence all lives and environment. Wastewater mostly generated from industries produces large amount of toxic substances, which are harmful to the environment and aquatic life. Phenol and 4-nitrophenol, which are disposed to sewage system without treatment, are generated from many industries. This poses health risks to aquatic organisms and human beings. Some of aqueous pollutants can be removed through adsorption technique using various adsorbents. In this work, a composite was prepared from coconut shell, clay and inorganics for removal of phenol and 4-nitrophenol from the aqueous solutions. The prepared composite was activated using KOH. The adsorbentwas characterised using Scanning Electron Microscopy-Energy Dispersive X-ray, Fourier Transforms Infrared Spectroscopy, X-ray Diffraction, pH of point of zero charge, and nitrogen adsorption-desorption. Effects of time, temperature, pH and concentrations were investigated using batch adsorption procedure. Kinetic models (pseudo-first order, pseudo-second order, Avrami), intra-particle diffusion, isotherm models (Langmuir, Freundlich, Dubinin-Raduskevich, Temkin, Liu and Sips) and thermodynamic equations were used to explain the adsorption data. Liu isotherm gave the best fit for both phenol and 4-nitrophenol. The maximum amounts adsorbed are 1665.364 mg g–1 (25 °C) and 892.275 mg g–1 (50 °C) for phenol and 4-nitrophenol, respectively. The pseudo-second order and Avrami described the kinetic data well for phenol and 4- nitrophenol, respectively. The adsorption process was endothermic and non-spontaneous. Two simulated industrial effluents were treated using the adsorbent. The percentages of effluents removal after treatment were 88 and 86% for phenol and 4-nitrophenol, respectively. This shows that the adsorbent can effectively and efficiently be used to treat industrial effluents.