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Abstract: It is well-known that chitosan consists of amino groups for the chelation of metal ions while NH2-MCM-41 has excellent adsorption selectivities for metals. This work compares both adsorption capacities and selectivities of chitosan and NH2-MCM-41. It has been found that chitosan has adsorption capacities of 1.76mmol/g, 1.03mmol/g and 1.30mmol/g for Cu2+, Ni2+ and Zn2+ respectively whereas NH2-MCM-41 has adsorption capacity of 1.52mmol/g, 0.8mmol/g and 0.83mmol/g for Cu2+, Ni2+ and Zn2+. The higher adsorption capacity in chitosan is attributed to its higher loading of amine groups. The single component adsorption isotherms were well-fitted using Freundlich model. The binary adsorptions of Cu2+–Zn2+ and Ni2+–Zn2+ systems showed similar adsorption selectivities for both adsorbents. However, chitosan has no preferential adsorption for Ni2+–Zn2+ system while NH2-MCM-41 has a good selectivity towards Zn2+. It is believed that the difference can be attributed to the heterogeneous surface of chitosan due to its organic nature. The multi-component adsorptions were best described by a multicomponent extended Freundlich model. Despite the surface functional group, this work indicates the importance of the adsorbent support on selective adsorption. [Copyright &y& Elsevier]

Abstract: Two types of activated carbons from tyre char (with or without sulphuric acid treatment) were produced via carbon dioxide activation with BET surface areas in the range 59–1118m2/g. Other characterisation tests include micropore and mesopore surface areas and volumes, pH, and elemental compositions, particularly heteroatoms such as nitrogen and sulphur. They were correlated to the adsorption capacity which were in the range of 0.45–0.71mmol/g (untreated) and 0.62–0.84mmol/g (acid-treated) for Acid Blue 25. In the case of larger-sized molecules like Acid Yellow 117, capacities were in the range of 0.23–0.42mmol/g (untreated) and 0.29–0.40mmol/g (acid-treated). Some tyre carbons exhibit a more superior performance than a microporous, commercial activated carbon (Calgon® F400). By modelling the dye adsorption equilibrium data, the Redlich–Peterson isotherm is adopted as it has the lowest SSE. Based on the surface coverage analysis, a novel molecular orientation modelling of adsorbed dyes has been proposed and correlated with surface area and surface charge. For the acid dyes used in this study, molecules were likely to be adsorbed by the mesopore areas. [Copyright &y& Elsevier]