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Graphene oxide (GO) was synthesized by modified the Hummers method and used as an effective adsorbent for removing direct blue 71 (DB 71) and methylene blue (MB) from water. Surface characteristics of the produced GO materials and related physiochemical properties of the organic dyes were systematically examined to reveal removal mechanisms. Thermodynamics, kinetics, and regeneration of GO adsorbent were also studied to disclose the nature of the adsorption and the reusability of adsorbent. GO adsorbed the cationic MB better than the anionic DB 71 mainly due to the electrostatic attraction between negatively charged GO's surface and the positively charged MB molecules. Langmuir isotherm better described MB and DB 71 adsorption than the Freundlich model. The adsorption capacities of GO of 476.19 mg/g (for MB) and 175.41 mg/g (for DB 71) were considerably higher than those of other adsorbents such as activated carbon, chitosan, and biochar. MB and DB 71 adsorption process was spontaneous, endothermic, and governed by both physisorption and chemisorption. GO could be regenerated by methanol and dilute HCl solutions, and reused as an efficient adsorbent. This study provides a comprehensive data on the MB and DB71 adsorption processes, and an efficient approach on the regeneration of GO adsorbent. [ABSTRACT FROM AUTHOR]

Author(s): Li-Min Lu [1]; Ling-Feng Mao [2]; Tuo Yang [1]; Jian-Fei Ye [1, 3, 4]; Bing Liu [1, 5]; Hong-Lei Li [6, 7]; Miao Sun [8, 9]; Joseph T. Miller [...]

In this study, reduced graphene oxide (rGO) was successfully produced from graphite precursor by chemical oxidation and exfoliation processes that were followed by a reduction process under mild conditions. SEM/EDX, XRD, FT-IR, BET, pHpzc were conducted to characterize the as-synthesized materials. Impacts of different factors such as contact time, temperature, pH of the solution, adsorbent load, and tetracycline (TC) concentration on TC removal efficiency were examined. Furthermore, the adsorption kinetics, thermodynamics, and isotherms were also investigated. As the result, the adsorption process of TC onto rGO was spontaneous, endothermic, and governed by both physisorption and chemisorption. The maximum uptake calculated from the Langmuir isotherm model was 58.03 mg/g. rGO material could be regenerated by using methanol and diluted NaOH solutions. The findings in this work provided complete data on the TC adsorption process onto rGO and the process of the recovery and reuse of rGO. [ABSTRACT FROM AUTHOR]

Abstract: Tetrastigma (Miq.) Planch. (Vitaceae) is a genus with ca. 100 species showing great morphological diversity. Previous molecular phylogenetic studies suggested that traditional classification systems are not consistent with the molecular phylogeny, and Tetrastigma is undergoing further systematic investigation. We traced the evolutionary trends of 20 morphological characters within a robust phylogenetic framework. Our results revealed that many morphological characters show either multiple transitions or few state changes, however, some characters show distinct variation. The two subgenera in Tetrastigma (subgen. Tetrastigma and subgen. Palmicirrata) based on unbranched/bifurcate versus digitately branched tendrils are not supported because subgen. Tetrastigma is paraphyletic. However, the unbranched versus bifurcate/digitately branched tendril is of taxonomic utility to characterize some of the major clades. Inflorescences in Tetrastigma appear axillary, but are leaf‐opposed on a compressed axillary shoot. We found most of the species in Tetrastigma retained the ancestral compound dichasial inflorescence, except those of clade IV that have derived pseudo‐umbellate inflorescences. Other characters including habit, leaf organization, and berry shape provide additional morphological support for the major clades. Our morphological analysis and recent molecular study suggest each of the five major clades within Tetrastigma be treated as distinct taxonomic sections (five sections in the genus). [ABSTRACT FROM AUTHOR]