Preparation and properties of a novel macro porous Ni2+-imprinted chitosan foam adsorbents for adsorption of nickel ions from aqueous solution.

In this study, novel macro porous Ni2+-imprinted chitosan foam adsorbents (F-IIP) were prepared using sodium bicarbonate and glycerine to obtain a porogen for adsorbing nickel ions from aqueous solutions. The use of the ion-imprinting technique for adsorbents preparation improved the nickel ion selectivity and adsorption capacity. We characterised the imprinted porous foam adsorbents in terms of the effects of the initial pH value, initial metal ion concentration, and contact time on the adsorption of nickel ions. The adsorption process was described best by Langmuir monolayer adsorption models, and the maximum adsorption capacity calculated from the Langmuir equation was 69.93mgg-1. The kinetic data could be fitted to a pseudo-second-order equation. Our analysis of selective adsorption demonstrated the excellent preference of the F-IIP foams for nickel ions compared with other coexisting metal ions. Furthermore, tests over five cycle runs suggested that the F-IIP foam adsorbents had good durability and efficiency.

Comparison of Co(2+) adsorption by chitosan and its triethylene-tetramine derivative: Performance and mechanism.

A cross-linked chitosan derivative (CCTS) was synthesized via cross-linking of epichlorohydrin and grafting of triethylene-tetramine. The adsorption performance and capacity of the raw chitosan (CTS) and its derivative were also investigated for removal of Co(2+) from aqueous solution. A maximum adsorbed amount of 30.45 and 59.51mg/g was obtained for CTS and CCTS, respectively under the optimized conditions. In addition, the adsorption kinetics for the adsorption of Co(2+) by CTS and CCTS were better described by the pseudo second-order equation. The adsorption isotherm of CCTS was well fitted by the Langmuir equation, but the data of the adsorption of Co(2+) onto CTS followed Freundlich and Sips isotherms better. Furthermore, the adsorbent still exhibited good adsorption performance after five regeneration cycles. Finally, Co(2+) removal mechanisms, including physical, chemical, and electrostatic adsorption, were discussed based on microstructure analysis and adsorption kinetics and isotherms. Chemical adsorption was the main adsorption method among these mechanisms.

Simultaneous absorption of NOx and SO2 from flue gas with pyrolusite slurry combined with gas-phase oxidation of NO using ozone.

NO was oxidized into NO(2) first by injecting ozone into flue gas stream, and then NO(2) was absorbed from flue gas simultaneously with SO(2) by pyrolusite slurry. Reaction mechanism and products during the absorption process were discussed in the followings. Effects of concentrations of injected ozone, inlet NO, pyrolusite and reaction temperature on NO(x)/SO(2) removal efficiency and Mn extraction rate were also investigated. The results showed that ozone could oxidize NO to NO(2) with selectivity and high efficiency, furthermore, MnO(2) in pyrolusite slurry could oxidize SO(2) and NO(2) into MnSO(4) and Mn(NO(3))(2) in liquid phase, respectively. Temperature and concentrations of injected ozone and inlet NO had little impact on both SO(2) removal efficiency and Mn extraction rate. Specifically, Mn extraction rate remained steady at around 85% when SO(2) removal efficiency dropped to 90%. NO(x) removal efficiency increased with the increasing of ozone concentration, inlet NO concentration and pyrolusite concentration, however, it remained stable when reaction temperature increased from 20°C to 40°C and decreased when the flue gas temperature exceeded 40°C. NO(x) removal efficiency reached 82% when inlet NO at 750 ppm, injected ozone at 900 ppm, concentration of pyrolusite at 500 g/L and temperature at 25°C.