Closing the loop: As(V) adsorption onto goethite impregnated coal-combustion fly ash as integral building materials

Abstract

Fly and bottom ash(es) are the most abundant generated by-products of coal combustion in thermal power plants. This investigation offers a sustainable solution of a double and circular use of industrial waste material in civil engineering practices; i.e., fly ash (FA) as an eco-efficiently, low-cost material for As(V) adsorption, as well as an additive in building materials. A goethite impregnated sample (FAG) was synthesized and optimized using the column precipitation procedure, then thoroughly, structurally and morphologically characterized using liquid nitrogen porosimetry (BET), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and Mossbauer spectroscopy (MS) techniques. The data from the equilibrium adsorption were fitted by linear and non-linear isotherm models; the optimal capacity of FAG/As(V) removal was calculated from the Langmuir model at 31.742 mg g(-1) for 45 degrees C. The kinetics of adsorption process has shown the pseudo-second-order kinetic model (PSO). The Weber-Morris model was applied to determine the intra-particle diffusion as a limiting step of reaction. The low pH dependant FAG leaching confirmed the efficient use of non-hazardous waste material in arsenic removal; furthermore, it also validated the new added value of the used/spent adsorbent as an adhesive in building materials possessing advanced mechanical properties.