Modelling adsorption of acid orange 7 dye in aqueous solutions to spent brewery grains

Adsorption of remazol brilliant blue on an orange peel adsorbent

“…Iqbal and Ashiq (2007) reported ΔSº negative values for the adsorption of the following dyes from aqueous solutions on activated carbon: alizarine red-S, methyl blue, methylene blue, eriochrome black-T, malachite green, phenol red and methyl violet, indicating that the randomness at the solid-solution interface decreased during adsorption. However in case of dye bromophenol blue, the entropy increased like in the present work and the same phenomenon was reported by Gupta et al (1997), Gupta et al (2003), Silva et al (2004), Bulut and Aydin (2006) for others dyes. These differences may be attributed to the physical and chemical characteristics of the dyes and adsorbents, which play an important role in adsorption.…”

“…The positive value of ΔSº suggested increased randomness at the solid/solution interface with some structural changes in the adsorbate and the adsorbent and an affinity of the adsorbent toward dye (Srivastava et al, 2006). Though the adsorption of dyes is currently described as an exothermic phenomenon (Jain et al, 2003;Iqbal and Ashiq, 2007), endothermic adsorption was also reported in the literature: acid orange 7 dye in aqueous solutions using spent brewery grains (Silva et al, 2004), methylene blue adsorption using wheat shells (Bulut and Aydin, 2006) and malachite green and basic red using activated carbon and activated slag (Gupta et al, 1997;Gupta et al, 2003). Iqbal and Ashiq (2007) reported ΔSº negative values for the adsorption of the following dyes from aqueous solutions on activated carbon: alizarine red-S, methyl blue, methylene blue, eriochrome black-T, malachite green, phenol red and methyl violet, indicating that the randomness at the solid-solution interface decreased during adsorption.…”

Removal of azo dye by a highly graphitized and heteroatom doped carbon derived from fish waste: Adsorption equilibrium and kinetics

“…While with increased contact time, AO7 molecules can reach all the adsorption sites of FWPC until saturation. A previous report is well agreed with the observation in the present study, in which high level of AO7 removal onto acid hydrolysed spent brewery grains was achieved at high initial concentrations and increased contact time (Silva et al, 2004a). Contour figure of AO7 adsorption efficiency was plotted (shown in Fig.…”

“…It is clear that high removal rate of AO7 (higher than 99%) was achieved with optimized range of initial AO7 concentration of 66e181 mg/L and contact time of 7e15 min. By comparing, the AO7 adsorption capacity onto FWPC is higher than those onto reported adsorbents in the literature (Aber et al, 2007;Elizalde-Gonz alez and Hern andez-Montoya, 2009;Hamzeh et al, 2012;Hsiu-Mei et al, 2009;Silva et al, 2004aSilva et al, , 2004bPadmesh et al, 2005). In addition, it is worth noting that the optimal contact time of AO7 adsorption onto FWPC in the present study is far shorter than that of other adsorbents (Aber et al, 2007;Elizalde-Gonz alez and Hern andez-Montoya, 2009;Hamzeh et al, 2012;Hsiu-Mei et al, 2009;Silva et al, 2004aSilva et al, , 2004bPadmesh et al, 2005), confirming that FWPC is very efficient for AO7 removal from aqueous solution.…”

“…where C e (mg/L) is the equilibrium concentration in the solution, q e (mg/g) is the AO7 adsorbed at equilibrium, b (mg/g) is the Hamzeh et al, 2012;Hsiu-Mei et al, 2009;Silva et al, 2004aSilva et al, , 2004bPadmesh et al, 2005).…”