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In this work, we report a room-temperature approach to synthesizing reduced graphene oxide/NiO (RGO/NiO) nanocomposites. The chemical structure of RGO/NiO nanocomposites were investigated by Transmission Electron Microscope (TEM), X-ray photoelectron spectroscopy (XPS), and X-ray power diffraction (XRD). It is shown by the experiment that the RGO/NiO nanocomposites have strong capacity to absorb the hexavalent chromium ion (Cr (VI)), the maximum adsorption capacity of Cr (VI) on RGO/NiO nanocomposites at pH = 4 and T = 25 °C can reach 198 mg g −1 , higher than any other currently reported. The adsorption kinetic data were well described by a pseudo-second-order model. Both Freundlich and Langmuir isotherm models were applied to the experimental data analysis, and the latter proved to be a better fit. The pH value markedly affected the adsorption behavior of RGO/NiO nanocomposites, but the effect of temperature was insignificant. The probable mechanism of synergistic adsorption of Cr (VI) ions was considered. These results suggest that RGO/NiO nanocomposites have the potential to be applied in industrial wastewater treatment. [ABSTRACT FROM AUTHOR]

The aim of the present work was to evaluate and compare of carbon materials for the ability to eliminate Cu (II) and Zn (II) ions from water. Ammonium peroxydisulphate ((NH 4 ) 2 S 2 O 8 )-treated carbon material (Ox-CM) was prepared from the combustion of forest branches and was compared with raw carbon material (CM). The adsorption isotherms and the influence of contact time, initial pH, and ionic strength for the adsorption of Cu (II) and Zn (II) were determined. The results of this work show that the removal ratios of Cu (II) for CM and Ox-CM after 2 h were 8.7 and 94.2%, respectively; and, those of Zn (II) for CM and Ox-CM after 2 h were 7.8 and 89.9%, respectively. The values of the parameters obtained for Cu (II) were based on the Langmuir isotherm saturated adsorption amount ( Q 0 ) and the adsorption equilibrium constant ( K L ): 27.47 mg/g and 0.4556 L/mg on Ox-CM; 3.66 mg/g and 0.2099 L/mg on CM, respectively. Those of Q 0 and K L for Zn (II) were as follows: 22.52 mg/g and 0.4978 L/mg on Ox-CM; 3.07 mg/g and 0.5560 L/mg on CM, respectively. In this work Ox-CM provided the optimal level of adsorption for Cu (II) and Zn (II) ions. [ABSTRACT FROM AUTHOR]

Adsorption of nitrobenzene (NB) on the NaOH-modified spent coffee ground (NaOH-SCG) was examined and the effects of contact time and adsorbent dose were investigated. The adsorption isotherm of NB on NaOH-SCG was compared with that of untreated SCG. The results from our study showed that the removal efficiencies of NB (25 mg/L) on SCG and NaOH-SCG after 2 h were 91.8% and 98.2%, respectively. The adsorption rate was very quick with the equilibrium of adsorption being achieved within about 30 min. The values of parameters obtained for NB from the Langmuir isotherm saturated adsorption amount and adsorption equilibrium constant were 117.2 mg/g, 0.0753 L/mg for SCG and 169.4 mg/g, 0.1815 L/mg for NaOH-SCG. NaOH-SCG (0.44 mmol/g) has fewer acidic functional groups than SCG (1.49 mmol/g). Therefore, the surface polarity of NaOH-SCG is low, thus makes this material more hydrophobic. The strong hydrophobicity of the NaOH-SCG surface might explain the high adsorption capacity for NB. As a result, this study has found that the NaOH-modified spent coffee ground has high adsorption ability for NB. [ABSTRACT FROM AUTHOR]

Abstract In recent years, various industrial activities have caused serious pollution to the environment. Due to the low operating costs and high flexibility, adsorption is considered as one of the most effective technologies for pollutant management. Agricultural waste has loose and porous structures, and contains functional groups such as the carboxyl group and hydroxyl group, so it can be invoked as biological adsorption material. Agricultural waste gets the advantages of a wide range of sources, low cost, and renewable. It has a good prospect for the comprehensive utilization of resources when used for environmental pollution control. This article summarized the current research status of agricultural waste in adsorbing pollutants, which pointed out the influencing factors of adsorption, expounded the adsorption mechanism of biological adsorption and introduced the related parameters of adsorption, proposed the application of adsorbents in engineering including adsorption in liquid and gas phases, at the same time it gave the future development prospect of agricultural waste as adsorbent. Graphical abstract Image 1 Highlights • Summarized the research progress of adsorbing inorganics, organics and gases on agricultural wastes. • Expounded the mechanism of adsorption inorganics and organics by agricultural wastes. • The application of agricultural waste as adsorbents in engineering was introduced. • Future prospects of agricultural wastes as adsorbents were discussed. [ABSTRACT FROM AUTHOR]