The Adsorption of Pollutants by Peat, Lignite and Activated Chars

Abstract

The ability of peat, lignite and activated chars made from peat and lignite to adsorb dyes and metals from wastewater and NO2 from air was investigated. Equilibrium isotherms were determined to assess the maximum adsorption capacity of the adsorbents for the pollutants. Kinetic studies for the adsorption of dyes and metal ions onto the adsorbents were undertaken in agitated batch adsorbers. Mass transport models were tested to predict the concentration decay curves in batch adsorbers. The models tested were single resistance models based on the assumption of a single external mass transfer coefficient and two resistance models which included an internal diffusion coefficient and an external mass transfer coefficient. The surface phenomena which influence the extent and the rate of uptake have been studied. The equilibrium capacity data conform to Langmuir plots. A previously proposed model was used to evaluate the external single resistance mass transfer model and was successfully applied to predict the adsorption of metal ions in single component systems under batch conditions. It has been shown that the assumption of negligible intraparticle diffusion is valid and that external film diffusion is the rate limiting step in describing the adsorption processes at high sorbent loadings. The same type of result is not observed for the adsorption of coloured organic matter onto peat where the sorption processes cannot be successfully modelled by use of a single resistance model and a two resistance model incorporating internal diffusion is required. The surface phenomena which influence the extent and the rate of uptake of NO2 have been studied. The type of chars produced and the activation processes affect the adsorption. As activation increases, micropore volume and surface area increase and the maximum capacity of the adsorbent increases. Surface area alone is not the only parameter which affects equilibrium uptake. © 1997 SCI.

The Adsorption Kinetics of Cethyltrimethylammonium Bromide (CTAB) onto Powdered Active Carbon

“…Therefore, the changes of k i,1 and k i,2 could be attributed to the adsorption stages of the exterior surface, interior surface and equilibrium, respectively. Allen et al (1997) thought that there were four separate regions depicting the mass transfer, i.e. external mass transfer effect, macropore diffusion, transitional pore diffusion and micropore diffusion.…”

Adsorption of copper, nickel and lead ions from synthetic semiconductor industrial wastewater by palm shell activated carbon

“…A number of adsorbent materials have been studied for their ability to remove heavy metals and they have been sourced from natural materials and biological wastes of industrial processes (Igbinosa and Okoh, 2009). These materials including: activated carbon (Uzun and Guzel, 2000;Goel et al, 2005;Issabayeva et al, 2007;Mondal et al, 2008), chitosan and carrageenan (Bong et al, 2004), lignite (Allen et al, 1997), kaolinite and ballclay (Chantawong et al, 2003), diatomite (Ulmanu et al, 2003), coconut fiber (Igwe et al 2007) and limestone (Aziz et al, 2004). However, adsorption by activated carbon had been reported as a technically and economically viable technology for heavy metal removal (Huang and Morehart, 1991;Bong et al, 2004).…”

Aqueous-Phase Sorption Behaviors of Cs<sup>+</sup>, Co<sup>2+</sup>, Sr<sup>2+</sup> and Cd<sup>2+</sup>ions on some Composite Ion Exchangers

“…Although the basic assumptions for these models were not fulfilled due to the heterogeneity of the sorbents surface, they were quite successful in predicting the experimental saturation capacities of the sorbents [20][21][22][23]. The Langmuir model is probably the best known and most widely applied sorption isotherm.…”