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This study developed a coagulation-flotation process for microalgae Chlorella sp. XJ-445 harvesting, which was composed of algal surface modification by combined use of Al 3+ and cetyltrimethylammonium bromide (CTAB) and followed dispersed bubble flotation. Dissolved organic matter (DOM) in the medium was firstly characterized and mainly consisted of hydrophilic low molecular weight molecules. The dosage of collector (CTAB) and coagulant (Al 3+ ) were optimized, and with the pretreatment of 40 mg Al 3+ and 60 mg CTAB per 1 g dry biomass without pH adjustment, a maximum flotation recovery efficiency of 98.73% can be achieved with the presence of DOM. Algal cells characterization results showed that the combined use of CTAB and Al 3+ largely enhanced the algal floc size, and exhibited higher degree of hydrophobicity, which favoured the flotation, and can be interpreted by DLVO (Derjaguin, Landau, Verwey and Overbeek) modelling. A benefit in fatty acid conversion was further found with the optimized coagulation-flotation process. It was suggested that this coagulation based flotation is a promising strategy for high-efficiency harvesting of microalgae., Competing Interests: We declare we have no competing interests.

The effects of growth phase on the lipid content and surface properties of oleaginous microalgae Botryococcus sp. FACGB-762, Chlorella sp. XJ-445 and Desmodesmus bijugatus XJ-231 were investigated in this study. The results showed that throughout the growth phases, the lipid content of microalgae increased. The surface properties like particle size, the degree of hydrophobicity, and the total concentration of functional groups increased while net surface zeta potential decreased. The results suggested that the growth stage had significant influence not only on the lipid content but also on the surface characteristics. Moreover, the lipid content was significantly positively related to the concentration of hydroxyl functional groups in spite of algal strains or growth phases. These results provided a basis for further studies on the refinery process using oleaginous microalgae for biofuel production.

New microscale zero-valent iron adsorbent on fly ash and bentonite matrix for removal of crystal violet (CV) and methylene blue (MB) was synthesized through direct reduction of iron oxide using coke and palm kernel shell. The adsorbent was prepared as cylindrical shaped pellets to remove the CV and MB from the aqueous solution. Nitrogen adsorption-desorption isotherm and scanning electron microscopy (SEM) studies showed that the adsorbent is highly porous, and the iron particles are finely dispersed on the supporting material surfaces. FTIR and UV studies indicated that the C=C bonds in CV and C=N + (CH 3 ) 2 bonds in MB were affected in the adsorption process. MB switched to the reduced MBH 2 species while CV was reduced to two small-size molecular compounds, explaining the higher CV adsorption in comparison to that of MB. The reduction of these compounds was coupled to the oxidation of Fe 0 to Fe 2 O 3 as revealed by XRD characterization of the adsorbent after adsorption. CV and MB adsorption isotherms fitted well with the Langmuir adsorption model. Different adsorption and reduction kinetic models were examined for the MB and CV removal processes. A better fit of the experimental data with the pseudo-second-order model was observed. CV and MB adsorption increased with temperature in the 30-50 °C range. At 50 °C, adsorption capacities of CV and MB reached to 89.9 and 42.8 mg/g, respectively. This new adsorbent showed a superior adsorption capacity for CV and MB when compared to other adsorbents.

In this work, a novel method for the quantitative determination of defects on graphene surfaces has been presented in order to provide accurate, reliable and quantitative information for the defects on graphene products. It was based on the selective adsorption of a specific polar organic ion (Sodium benzenesulfonate) on the edges and defects on graphene surfaces, and the atomic force microscopy (AFM) imaging of the adsorption. By means of an image processing software, the AFM images could be analyzed and the areas as well as area percentages of the defects on the graphene surfaces could be determined., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Water splitting is the key step towards artificial photosystems for solar energy conversion and storage in the form of chemical bonding. The oxidation of water is the bottle-neck of this process that hampers its practical utility; hence, efficient, robust, and easy to make catalytic systems based on cheap and earth-abundant materials are of exceptional importance. Herein, an in situ generated cobalt catalyst, [Co II (TCA) 2 (H 2 O) 2 ] (TCA=1-mesityl-1,2,3-1H-triazole-4-carboxylate), that efficiently conducts photochemical water oxidation under near-neutral conditions is presented. The catalyst showed high stability under photolytic conditions for more than 3 h of photoirradiation. During electrochemical water oxidation, the catalytic system assembled a catalyst film, which proved not to be cobalt oxide/hydroxide as normally expected, but instead, and for the first time, generated a molecular cobalt complex that incorporated the organic ligand bound to cobalt ions. The catalyst film exhibited a low overpotential for electrocatalytic water oxidation (360 mV) and high oxygen evolution peak current densities of 9 and 2.7 mA cm -2 on glassy carbon and indium-doped tin oxide electrodes, respectively, at only 1.49 and 1.39 V (versus a normal hydrogen electrode), respectively, under neutral conditions. This finding, exemplified on the in situ generated cobalt complex, might be applicable to other molecular systems and suggests that the formation of a catalytic film in electrochemical water oxidation experiments is not always an indication of catalyst decomposition and the formation of nanoparticles., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

CoAl-layered double hydroxide/fluorinated graphene (CoAl-LDH/FGN) composites were fabricated via a two-step hydrothermal method. The synthesized CoAl-LDH/FGN composites have been characterized by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), field-emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), and electrochemical measurements. The results indicated that the fluorinated carbon with various configuration forms were grafted onto the framework of graphene, and the C-F bond configuration and fluorine content could be tuned by the fluorination time. Most of semi-ionic C-F bonds were formed at an appropriate fluorination time and, then, converted into fluorine rich surface groups (such as CF 2 , CF 3 , etc.) which were electrochemically inactive as the fluorination time prolonged. Moreover, the CoAl-LDH/FGN composites prepared at the optimal fluorination time exhibited the highest specific capacitance (1222 F/g at 1 A/g), the best rate capability, and the most stable capacitance retention, which offered great promise as electrode materials for supercapacitors.

The adsorption of Hg 2+ on natural molybdenum disulfide has been studied using atomic force microscope (AFM). The AFM imaging clearly illustrated the adsorption of Hg 2+ on the surface of molybdenum disulfide, and also hydration layers on the surfaces. It was found that the presence of a hydration layer on molybdenum disulfide surfaces hindered the Hg 2+ adsorption. Also, it was observed that the Hg 2+ adsorbed appeared in the form of multilayers. The first adsorbed Hg 2+ layer might be mainly attributed to the complexation of Hg 2+ with S atoms exposed on molybdenum disulfide surfaces, while the second one might be due to the electrostatic interaction between negatively charged molybdenum disulfide and the cation Hg 2+ .

Arsenite (As(III)) is toxic in drinking water, which becomes an environmental concern worldwide. This work was to synthesize porous hematite through the calcination of natural goethite concentrate for As(III) adsorption, including adsorption kinetics, isotherms and the influence of pH and temperature. The calcination was performed at 300 °C for 180 min, producing porous hematite with large amount of micropores. The maximum adsorption capacity of As(III) on porous hematite was achieved at pH 6.0 and 25 °C, about 14.46 mg g -1 , compared with 2.965 mg g -1 on the original goethite concentrate. The improvement might be attributed to the formation of micropores and thus the increase in the surface area. Also, it was found that the adsorption was strongly pH dependent and reduced with increasing temperature. It is indicated that the low-cost porous hematite has great potential in As(III) removal from contaminated water., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

As(V) adsorption inside the pores of porous hematite in water has been studied in this work. This study was performed on nonporous hematite and porous hematite prepared from the thermal decomposition of goethite and siderite through the measurements of adsorption isotherm, SEM-EDX, XRD and BET. The results demonstrated that the As(V) adsorption was difficult to be realized inside pores if they were too small. This observation might be due to that the pore entrances were blocked by the adsorbed ions and thus the inside surfaces became invalid for the adsorption. Only if the pore size is large enough, the effective surface area inside pores would be close to that on non-porous hematite for As(V) adsorption. In addition, it was found that siderite is better than goethite for preparing porous hematite with thermal decomposition as adsorbent for arsenic removal., (Copyright © 2016 Elsevier B.V. All rights reserved.)

The relationship between the defects of reduced graphene oxide (RGO) and the oxidation degree of graphite in the preparation of graphene with chemical conversion method has been studied in this work. This study was performed on an artificial graphite through the measurements of X ray diffraction, Raman spectroscopy and particle size analysis. The experimental results have shown that there indeed was a close relationship between the defects and the oxidation degree, which appeared in the form of S-type curve. Also, it was found that a low KMnO4 addition would lead to a partial oxidation of graphite, leaving defects mainly on the edges of RGO; with a high KMnO4 addition, the defects on RGO mostly appeared on the surfaces., (Copyright © 2015 Elsevier Inc. All rights reserved.)

The aim of this study was to identify the most promising species as biodiesel feedstock for large-scale cultivation in north China. Eight species of microalgae, selected on the basis of indoor screening, were tested for lipid productivity and the suitability of their fatty acid profiles for biodiesel production under outdoor conditions. Among them, three species Desmodesmus sp. NMX451, Desmodesmus sp. T28-1 and Scenedesmusobtusus XJ-15 were selected for further characterization due to their possessing higher lipid productivities and favorable biodiesel properties. The best strain was S. obtusus XJ-15, with highest biomass productivity of 20.2gm(-2)d(-1) and highest lipid content of 31.7% in a culture of 140L. S. obtusus XJ-15 was further identified as the best candidate for liquid biofuel production, characterized by average areal growth rate of 23.8gm(-2)d(-1) and stable lipid content of above 31.0% under a scale of 1400L over a season., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

The adsorption of the gold-cyanide complex ion (Au(CN)(2)(-)) on sulfur-impregnated activated carbon in aqueous solution has been studied in order to find a better adsorbent for the gold cyanidation process for extracting gold from ores. This study was performed using sulfur-impregnated activated carbon (SIAC 8.0) made from high-sulfur petroleum coke and an artificial aqueous solution of Au(CN)(2)(-). The experimental results have shown that Au(CN)(2)(-) strongly adsorbed onto the SIAC 8.0, leading the gold adsorption capacity of the SIAC 8.0 to be 2.25x that on conventional activated carbon. It has been also found that the adsorption fit the Langmuir isotherm well, and the adsorption density of Au(CN)(2)(-) on the SIAC 8.0 in aqueous solution increased with increasing temperature, suggesting chemical adsorption. The chemical adsorption might be attributed to the formation of S-Au-CN on SIAC 8.0 surfaces through the covalent bond between the gold atom of the ion and the sulfur in the molecular structure of the SIAC 8.0. In addition, the desorption test has demonstrated that the majority of the adsorption was irreversible, which depended on the density of the adsorption sites on the SIAC., (Copyright 2010 Elsevier Inc. All rights reserved.)