The ability of activated carbon from coconut shell to adsorb Cr(VI) from aqueous environment has been ameliorated by treating the carbon with hydrobromic acid. The best carbon is gained by soaking activated carbon in 0.3 mol L−1 HBr solution at 80°C for 13 h followed by being carbonized at 600°C in nitrogen for 1.5 h. The Cr(VI) adsorbed at equilibrium by the best as‐prepared carbon is 11.32 mg g−1 while that by the original one is 7.801 mg g−1. Characterization results manifest that the treatment with HBr solution leads to the increase of acidic groups and the decrease of basic groups on the carbon surface. The treatment with HBr solution produces many lactonic groups on the carbon. BET determination indicates that some micropores and mesopores are generated by the treatment with HBr solution. The increase of acidic groups and magnification of surface area is ascribed to the improvement of the ability to adsorb Cr(VI) ions. Lactonic groups and micropores play a key role in adsorbing Cr(VI) from water.

Diethylenetriaminecobalt(II), [Co(DETA)2]2+, formed by diethylenetriamine (DETA) coordinating with Co(II) ion, can be used to remove NO from flue gas. Diethylenetriaminecobalt(II) is capable of binding NO to form metal nitroso complexes. The determination of the equilibrium constant of the reaction between [Co(DETA)2]2+ and NO is important to the development of the technology for the elimination of NO from exhausted gas streams with diethylenetriaminecobalt solution. In this paper, the equilibrium constants of this reaction have been determined by a series of experiments in a bubble reactor at the range of 30–70°C under atmospheric pressure in the [Co(DETA)2]2+ solution of pH 7.5. All experimental data are in good agreement with the following equation: KnormalT=1.8619×10−6exp4677.52TL⋅mol−1, where the changes in enthalpy and entropy are ΔH0 = −38.89 kJ ⋅ mol−1 and ΔS0 = −109.7 J ⋅ K−1 ⋅ mol−1, respectively.

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