Metal Adsorption by Coal Fly Ash: The Role of Nano-sized Materials

Abstract

Nano-sized particles (1-100 nm) comprise a considerable fraction of coal fly ash (CFA). They are unique due to their large surface area and higher reactivity compared to larger CFA particles. As they are formed by nucleation of volatilised elements or through chemical reactions, nano-scale CFA particles have been shown to take up greater quantities of elemental ions and bind them more strongly than larger particles, diminishing the fraction of desorbed ions. Despite this and the large volume of literature on acid mine drainage (AMD) treatment using CFA, little is described about the specific role of nanoparticles in this process. This chapter therefore sets out to highlight this, beginning by delineating nanoparticle characteristics that make them good adsorbents followed by details of their formation and action in metal adsorption.

Application of coal fly ash for trace metal adsorption from wastewater: A review

“…The application of CFA as an adsorbent material is attributed to the inorganic or organic nano-sized particles (ultrafine glassy spheres, cenospheres, nanotubes, and carbonaceous nanospheres) with surface area as high as 1000 m 2 . g −1 that can adsorb trace metals from wastewater and can be incorporated into other materials or as a synthesized composite to enhance its removal efficiency [ 49 , 90 , 91 ].…”

“…The kinetic and isotherm models of CFA-based nanomaterials dominating others were pseudo-second order and Langmuir models, respectively. The pseudo-second order kinetic model followed in some studies assumes that the rate-limiting step is chemisorption in which adsorption increases with an increasing temperature and predicts the behaviour over the whole range of adsorption process [ 91 , 92 , 94 ]. Optimum pH and removal efficiency ranged between 3.0 and 8.0, and 40.00–97.41 %, respectively.…”

“…In recent years, the use of CFA has received a lot of attention due to its potential to reduce the environmental burden of solid waste disposal, while contributing to economic gain [ 74 , 75 ]. CFA can work independently as an adsorbent as it contains nanosized particles (1–100 nm) with higher reactivity and large surface area and can also be incorporated into other adsorbent materials to improve their effectiveness [ 76 ]. The high efficiency of CFA-based adsorbents is also attributed to their high surface area which can be as high 1000 m 2 g −1 , their alkaline nature and capacity for adsorption/co-precipitation of elemental ions.…”