Use of fly ash and fly ash agglomerates for As(III) adsorption from aqueous solution

The objective of the present study is to assess the efficiency of fly ash and fly ash agglomerates to remove arsenic(III) from aqueous solution. The maximum static uptakes were achieved to be 13.5 and 5.7 mgAs(III)/adsorbent for nonagglomerated material and agglomerated one, respectively. Isotherm studies showed good fit with the Langmuir (fly ash) and the Freundlich (fly ash agglomerates) isotherm models. Kinetic studies indicated that the sorption of arsenic on fly ash and its agglomerates follows the pseudo-second-order (PSO) chemisorption model (R2 = 0.999). Thermodynamic parameters revealed an endothermic nature of As(III) adsorption on such adsorbents. The adsorption results confirmed that fly ash and its agglomerates can be used for As(III) removal from aqueous solutions. Fly ash can adsorb more arsenic(III) than agglomerates, which are easier to use, because this material is less dusty and easier to separate from solution.

Modelling of Catalyst Pellet Deactivation: An Irreversible Chemisorption Model

Deactivation caused by irreversible chemisorption of a catalyst poison of a single catalyst pellet is studied. Diffusion and shell progressive models are discussed. A numerical procedure is proposed and theoretical and experimental results are compared. Experimental data are obtained by measuring concentration and temperature time dependences due to thiophene poisoning in benzene hydrogenation over Ni/alumina catalyst in one pellet CSTR reactor.