Optimization of preparation technology for modified coal fly ash and its adsorption properties for Cd2+

A Mineral By-Product from Gasification of Poultry Feathers for Removing Cd from Highly Contaminated Synthetic Wastewater

“…Increasing Cd concentration increases the driving force to overcome resistance to mass transfer between the ash and wastewater, resulting in increasing metal sorption. With increasing initial metal concentrations, the binding sites on the adsorbent are gradually occupied by metal until saturation occurs [26]. Our observations are consistent with reports on Cd adsorption onto different adsorbents, e.g., pretreated rice straw and rice husk [55], chicken-manure-derived biochars [58] and coal fly ash [27].…”

“…where: q e is the amount of Cd adsorbed at equilibrium (mg/g), q t is the amount of Cd adsorbed at a specific contact time (mg/g), k 1 is a rate constant (1/min), k 2 is a rate constant (g/mg/min), h is the initial adsorption rate (mg/g/min), k i is the intraparticle diffusion rate constant (mg/g/min 1/2 ), C i is constant related to the thickness of the boundary layer (mg/g) and t is the contact time (min) [26]. Equilibrium adsorption models: To evaluate and compare the adsorption capacities of Cd and to provide some insight into adsorption mechanisms, the following models were used:…”

“…The R 2 value for the pseudo-second-order model was equal to 1, indicating that Cd sorption onto poultry ash was well described by this model. Many other papers also indicate that the kinetics of sorption of Cd onto different adsorbents is successfully described with the pseudo second-order model (e.g., [26,55,64]). With the use of a pseudo-second-order model, it can be assumed that chemisorption (as precipitation and adsorption onto ash solids) was the main mechanism of Cd removal from the wastewater.…”

“…Ca loss was highest, while losses of S, P and K were lower. order model (e.g., [26,55,64]). With the use of a pseudo-second-order model, it can be assumed that chemisorption (as precipitation and adsorption onto ash solids) was the main mechanism of Cd removal from the wastewater.…”

“…The ash was prepared in laboratory conditions, without detailed characterization. Most existing studies have evaluated the adsorption characteristics of heavy metals with the use of fly ash from coal combustion [24,25], chemically modified coal fly ash [26,27] and fly ash and bottom ash from wood pellet thermal power plants [28]. The type of feedstock affects the chemical composition and physical properties of fly ash and its adsorption performance [29].…”