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In the two-step production of polyaluminum chloride, the insoluble solid in raw material will become waste residue. The landfill could cause pollution of non-point source and groundwater. Meanwhile, reports of Cr(VI) contamination in drinking water due to industrial pollution occur frequently. In this study, a new adsorbent was prepared by calcination of polyaluminum chloride residue. The new adsorbent was characterized, and the adsorption capacity of Cr(VI) in water was analyzed. The analysis results showed that the new adsorbent not only could provide a larger specific surface area (6 times higher than polyaluminum chloride residue) and more active sites, but also could maintain the stability of its structure. The second-order adsorption kinetic model and Langmuir adsorption isotherm model could well describe the adsorption process of Cr(VI) on the new material. The Cr(VI) adsorption by the new adsorbent is a spontaneous endothermic process. Compared with other commonly used adsorbents, the cost of new adsorbent was 1.308 $/kg, and it had obvious economic advantages. This study explored a new way of resource utilization of polyaluminum chloride residue, and the adsorption capacity could still be maintained above 2.6 mg/g after 5 times of regeneration, indicating that the material has engineering application potential. This paper could provide more technical options for environmental protection engineers, provide ideas for environmental researcher, and solve the problem of water pollution by combining with other water treatment technologies. [ABSTRACT FROM AUTHOR]

As lead-containing products, such as lead batteries, are widely used, water pollution problems caused by Pb2+ show a significant threat to the ecosystem and human health. To overcome this serious problem, the modified poly(methyl methacrylate) (PMMA)/chitosan (CS) composites were prepared by adding CS into the PMMA matrix as functional filler and surface modification. The structure, thermal stability, size, morphology and adsorption properties of the modified PMMA/CS composites were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, and inductively coupled plasma optical atomic emission spectrometry. The results indicated that the modified PMMA/CS composites had a uniform size of about 1 μm and showed quite good thermal stability. In addition, the Pb2+ removal of the modified PMMA/CS composite reached up to 98% when the initial Pb2+ concentrations are under 100 mg l−1. The results of the adsorption isotherms indicated that the Langmuir isotherm fits best to the experimental data when compared with the Freundlich isotherm and Temkin isotherm. All these results demonstrate that modified PMMA/CS has a good adsorption property and can be a promising adsorbent for chelating Pb2+. [ABSTRACT FROM AUTHOR]

Density functional theory calculations were performed to study the adsorption and dissociation of methane as well as syngas formation over Ni(111) and NiPt(111) aiming to gain insight into the effect of Ni(111) surface alloying on partial oxidation of methane (POM). Results show that Pt-doped Ni(111) surface is beneficial to the adsorption of CH x and H species while unfavorable to the desorption of H 2 . The process of CH → C + H is found to be the rate-limiting step of successive dehydrogenation of methane on NiPt(111). Especially, the processes of CH 4 → CH 3 + H and CH 3 → CH 2 + H proceed more easily on NiPt(111) than on Ni(111). Three potential pathways for CO formation in the POM process were proposed and calculations identified that CH + O → CHO → CO + H are likely to be the main routes for CO formation on Ni(111) with CH + O → CHO as the rate-limiting step. Further calculations reveal that the formation of CO and H 2 may be more difficult on NiPt(111) than on Ni(111). [ABSTRACT FROM AUTHOR]