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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]

Abstract: The effects of modification by HNO3 oxidization on the physico-chemical properties of activated carbon fiber (ACF), the adsorption of aniline, pyridine and phenol on ACF and modified ACF, as well as the influence of textural properties on adsorption by comparing ACF with an activated carbon are investigated. The adsorbents are characterized using N2 adsorption, Boehm titration, diffuse reflectance infrared Fourier transform spectroscopy, and temperature-programmed desorption. The pore properties of ACF are not significantly changed by the modification; however, it increases greatly the oxygenated acidic groups on the surface of ACF. The uptake for each aromatic compound by the modified ACF is lower than on ACF. This is mainly due to the decrease of dispersive interaction, more water cluster formed to block entry of compounds into micropores or competition between water and compounds adsorbed onto the surface of ACF because of hydrophilic increase of ACF. The maximum uptake for the aromatic compounds decreases with the increase in aqueous solubility of the adsorbates. K, a Langmuir parameter, is indirectly associated with the surface chemistry of ACF. For the aromatic compounds mentioned, the uptake increases with the micropore volume of carbon materials. [ABSTRACT FROM AUTHOR]