Rapid flocculation-sedimentation of microalgae with organosilane-functionalized halloysite

Microalgae is a promising feedstock of biofuel for alternating fossil fuels. The major challenge of microalgal biofuels for commercial applications is in designing an efficient harvesting method with high economic feasibility. In this study, a rapid flocculation-sedimentation harvesting method induced by organosilane-functionalized halloysite flocculant was achieved for Scenedesmus dimorphus harvest. The harvesting efficiency was significantly influenced by the pH of microalgal dispersion and the dosage of flocculant. The optimized harvesting condition was pH 3.0 with flocculant dosage of 1.0 g.g(-1) cell dry mass. Under the optimized harvesting condition, microalgae rapidly reached 93% harvesting efficiency within 0.5 min of settling time, and reached 98% harvesting efficiency within 2 min of settling time. The rapid flocculation was attributed to the charge neutralization of the negatively-charged microalgae cells by the positively-charged organosilane-functionalized halloysite flocculant and to the sweep flocculation by organosilane-functionalized halloysite flocculant. The organosilane-functionalized halloysite flocculant did not affect the lipid extraction of microalgae, and not contaminate the extracted residuals. The organosilane-functionalized halloysite flocculant is of high efficient, cost-effective, and eco-friendly, makes it be of promising application for commercial microalgae harvesting.</p

High Efficiency Uranium(VI) Removal from Wastewater by Strong Alkaline Ion Exchange Fiber: Effect and Characteristic

In this study, we analyzed the removal efficiency of uranium(U(VI)) in wastewater at relatively low concentrations using strong alkaline ion exchange fiber (SAIEF). Static tests showed that the strong alkali fibers can purify U(VI) containing wastewater in a concentration range of 20–100 mg L−1 with an optimal pH of 10.5 and contact time of 15–30 min. Adsorption and desorption cycling tests indicated that, adsorbed uranium is easily desorbed by 0.1 mol L−1 HCl, and the fiber still maintained the original adsorption efficiency after eight cycles. According to dynamic penetration test results, the SAIEF saturation adsorption capacity was 423.9 mg g−1, and the effluent concentration of uranium through two series columns was less than 0.05 mg L−1, reaching the national standard for non-receiving water (GB23727-2009) SEM-EDS and FTIR analysis revealed that the functional group of SAIEF is CH2N+(CH3)3Cl−. Addotionally, the major forms of fiber exchange adsorption are (UO2)2CO3(OH)3−, UO2(CO)34− and UO2(OH)3−. The results indicate that the SAIEF is an excellent material for uranium removal

Highly sensitive colorimetric detection of atmospheric sulfate formation-involved substances using plasmonic molybdenum trioxide nanosheets

The ongoing urban air pollution has resulted in an increased demand for detecting atmospheric sulfate formation-involved substances. Here, we present a series of colorimetric assays based on plasmonic MoO3-x nanosheets for visual colorimetric detection of atmospheric sulfate formation-involved substances, including hydrogen peroxide (H2O2), Fe2+/Fe3+, bisulfite (HSO3−), and sulfur dioxide (SO2). We show that the plasmonic MoO3-x nanosheets with blue color can be oxidized by hydroxyl radicals ([rad]OH) generated by the Fenton reaction between Fe2+/Fe3+ and H2O2 to produce colorless MoO3 nanosheets, resulting in a distinct absorbance change. However, when HSO3−/SO2 is introduced, the [rad]OH will react with them to yield sulfate, which inhibits the oxidation of MoO3-x nanosheets, leading to the color recovery. Using these detection systems, we determine H2O2, Fe2+, Fe3+, and HSO3− with detection limits of 60 nM, 50 nM, 400 nM, and 1 μM, respectively. Especially, SO2 is selectively assayed with an ultralow detection limit, down to 50 ppb level. In addition, the present colorimetric assay is further utilized to detect SO2 in real air with a good accuracy to demonstrate the practicality of the colorimetric method

3, 3\u27-Diaminobenzidine with dual o-phenylenediamine groups: two in one enables visual colorimetric detection of nitric oxide.

Nitric oxide (NO) plays an important role in the generation of smog and ozone. Although great efforts have been made to determine NO by using o-phenylenediamine (OPD)-based fluorescent probes, more simple and reliable colorimetric assays for detection of NO are extremely scarce because a single OPD structure cannot produce enough optical absorption for chromogenesis. In this study, we report an innovative two-in-one visual colorimetric methodology. Commercially available 3,3\u27-diaminobenzidine (DAB) with two OPD structures in a single molecule is selected as the colorimetric probe, and it reacts with NO via diazo-coupling reaction to generate 1H,3\u27H-[5,5\u27]bibenzotriazolyl because of the increase of conjugated double bonds, accompanying a distinct color change from colorless to brownish yellow. This two-in-one colorimetric assay can determine NO at a concentration as low as 3 ppm by the naked eye and 40 ppb by UV-vis spectrometry, which is the lowest limit of detection (LOD) among reported colorimetric assays for NO. Moreover, the present two-in-one visual colorimetric assay also has good selectivity toward NO over other common potential gas interferents such as C

Co(II) triggered radical reaction between SO\u3csub\u3e2\u3c/sub\u3e and o-phenylenediamine for highly selective visual colorimetric detection of SO\u3csub\u3e2\u3c/sub\u3e gas and its derivatives

Rapid, reliable, and highly selective detection of SO2 and its derivatives has an especially important practical significance in terms of environmental monitoring and human health. In this study, we describe a novel Co2+ triggered radical reaction pathway for visual colorimetric detection of SO2 and SO32−. The reaction between Co2+ and SO2 or SO32− with the assistance of dissolved oxygen produces highly active sulfate radical, leading to the oxidation of o-phenylenediamine (OPD). The oxidation products containing 2,3-dinitro-phenazinemethane, OPD dimer, and OPD trimer show strong UV–vis absorption. Consequently, SO2 and SO32− are quantitatively determined using the Co2+-OPD colorimetric detection system. This colorimetric assay exhibits a 60–650 μM and 30–70 ppm linear ranges for detection of SO32− and SO2, respectively. The corresponding limit of detection is calculated to be 4.07 μM and 1.26 ppm for SO32− and SO2. What is more, a distinct color change can be found at a SO32− concentration of 50 μM by the naked-eye observation. The specific radical detection guarantees that the present colorimetric assay has a good anti-interference ability over common inorganic ions and gases

Counterion-Mediated Decompaction of Liquid Crystalline Chromosomes

Liquid crystalline phases of DNA and nucleosome core particles can be formed in vitro, indicating the crucial roles of these phases in the maintenance and compaction of genomes in vivo. In the present study, sequential levels of liquid crystalline decompaction were identified in highly purified nuclei of Karenia papilionacea in response to the gradual chelation of divalent counterions by ethylenediaminetetraacetic acid (EDTA); the decompaction was observed using polarizing light microscopy, confocal laser scanning microscopy, and transmission electron microscopy and further confirmed utilizing microcalorimetry. Nested fibrous coils in 150nm arc-like bands of chromatin were observed in the early stages of chromosomal decompaction. The microcalorimetry spectra of isolated nuclei revealed that the dynamic processes of nuclear decompaction occurred in a nonlinear manner; in addition, an EDTA-sensitive thermal transition between 60 degrees C-70 degrees C, corresponding to a liquid-crystalline-phase transition of chromosomes, was found. The results suggested that nested coils of fibrous chromatin filaments are responsible for the establishment and stabilization of the liquid crystalline and bire-fringence features of the chromosomes of dinoflagellates. The results also indicated that positively charged divalent counterions play significant roles in modulating liquid crystalline phases to compact the chromosomes of dinoflagellates

Histone-like Protein HCcp3-induced Liquid Crystalline DNA Condensation

From prokaryotes to eukaryotes, the DNA condensation process by basic proteins is essential to store the genome in vivo. The surface charge inversion with a DNA/HCcp3 charge ratio of 0.7/1 indicates a role for HCcp3-mediated counter ion-driven mechanism in DNA condensation. The formation of the cholesteric liquid-crystalline phase of DNA HCcp3 complexes occurred when DNA charges were neutralized. The results suggest that DNA condensation processes by HCcp3 can be divided into two distinctive binding stages: the first state, prior to condensation, involves an entropy-driven binding process of HCcp3 to the DNA, while the second state is an electrostatically driven condensing and assembling process

Selective loading of 5-fluorouracil in the interlayer space of methoxy-modified kaolinite for controlled release

Methoxy-modified kaolinite was used as a novel carrier for anticancer drug 5-fluorouracil (5FU). The selective loading of 5FU into the interlayer space of methoxy-modified kaolinite was achieved because the weakly bonded 5FU on the external surface was removed off by facile water rinse. The intercalated 5FU has strong affinity (electrostatic force and hydrogen bonding) with the interlayer surface of kaolinite, and its release was controlled because of the diffusion restriction of the kaolinite lamellar layers and the strong affinity between 5FU and kaolinite. The controlled release of 5FU from methoxy-modified kaolinite in simulated colonic fluid (pH 5.5) makes it be of potential use to administer an oral formulation of 5FU for colon specific delivery