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Abstract: The adsorption of 1-naphthylamine, 1-naphthol and phenol on as-prepared and oxidized multiwalled carbon nanotubes (MWCNTs) has been investigated. The results illustrated that both as-prepared and oxidized MWCNTs showed high adsorption capacity for the three ionizable aromatic compounds (IACs) studied. Oxidation of MWCNTs increased the surface area and the pore volume, and introduced oxygen-containing functional groups to the surfaces of MWCNTs, which depressed the adsorption of IACs on MWCNTs. Both Langmuir and Freundlich models described the adsorption isotherms very well and the adsorption thermodynamic parameters (ΔG°, ΔH° and ΔS°) were measured. The adsorption for 1-naphthylamine, 1-naphthol and phenol is general spontaneous and thermodynamically favorable. The adsorption of phenol is an exothermic process, whereas the adsorption of 1-naphthylamine and 1-naphthol is an endothermic process. Results of this work are of great significance for the environmental application of MWCNTs for the removal of IACs from large volume of aqueous solutions. [Copyright &y& Elsevier]

Abstract: ZSM-5 zeolite is characterized by XRD, FT-IR and acid–base titration in detail. The results show that the sorption site distribution of ZSM-5 zeolite is affected by ionic strength obviously; the main sorption site are =XNa, =SOH and =SO− in all pH ranges. The sorption experiments of Eu(III) on ZSM-5 zeolite indicate that the sorption is strongly dependent on pH value and on ionic strength (ranged from I =0.001 to 0.05mol/L NaClO4) under ambient conditions. The sorption edges of Eu(III) on ZSM-5 zeolite in 0.1 and 0.01mol/L NaClO4 and the sorption isotherm in 0.01mol/L NaClO4, respectively, were modeled using a quasi-mechanistic sorption model (1-site protolysis non electrostatic surface complexation and cation exchange (1-SPNE SC/CE) model). The Eu(III) sorption edges in different ionic strengths could be modeled in the pH range 3–10 using cation exchange reactions for Eu3+/Na+ and three surface complexation reactions on the sorption sites by forming =SOEu, =SOEu(OH)+ and =SOEu(OH)2 inner-sphere surface complexes successively. The Eu(III)/ZSM-5 zeolite EXAFS analysis indicates that Eu(III) on ZSM-5 zeolite can be simulated (R =0.045) by assuming a number of coordination oxygen N =7.7(5) at d(Eu–O)=2.31Å (σ =0.01Å). [Copyright &y& Elsevier]

Abstract: Attapulgite was investigated to remove Ni2+ from aqueous solutions because of its strong sorption ability. Herein, the sample of attapulgite was modified with ammonium citrate tribasic (ACT) and used as an adsorbent to remove Ni2+ from aqueous solutions. XRD and FTIR analysis indicated that ACT was successfully grafted on attapulgite surfaces. The results indicated that ACT–attapulgite was better than bare attapulgite in the removal of Ni2+ from aqueous solutions. Sorption of Ni2+ on ACT–attapulgite was mainly dominated by ion exchange or outer-sphere complexes at low pH values, and by inner-sphere complexes or surface precipitation at high pH values. The thermodynamic data indicated that the sorption of Ni2+ to ACT–attapulgite hybrids was an endothermic process and was enhanced with increasing temperature. ACT–attapulgite is a suitable material for the preconcentration of Ni2+ from large volume of solutions and can be used in wastewater treatment because of its negative surface charge and large surface areas. [Copyright &y& Elsevier]