Yi Tang

Hexavalent chromium removal from aqueous solution by algal bloom residue derived activated carbon: Equilibrium and kinetic studies

A novel approach to prepare activated carbon from blue-green algal bloom residue has been tried for first time and its adsorption capability to remove hexavalent chromium Cr(VI) from aqueous solution has been examined. For this algal bloom residue derived activated carbon, the physical characters regarding adsorption capability were analyzed by scanning electron microscope (SEM), energy dispersive X-ray spectroscope (EDS) and Fourier transform infrared (FTIR) spectroscopy. Batch studies showed that initial pH, absorbent dosage, and initial concentration of Cr(VI) were important parameters for Cr(VI) absorption. It was found that initial pH of 1.0 was most favorable for Cr(VI) removal. The adsorption process followed the pseudo-second-order equation and Freundlich isotherm. The maximum adsorption capacity for Cr(VI) was 155.52 mg g(-1) in an acidic medium, which is comparable to best result from activated carbons derived from biomass. Therefore, this work put forward a nearly perfect solution which on one hand gets rid of environment-unfriendly algae residue while on the other hand produces high-quality activated carbon that is in return advantageous to environment protection.

Flocculation of harmful algal blooms by modified attapulgite and its safety evaluation.

Natural attapulgite (N-AT) and modified attapulgite (M-AT) were used in this study to evaluate their flocculation efficiencies and mechanisms in freshwater containing harmful algal blooms through conventional jar test procedure. The experimental results showed that the efficiency of flocculation can be significantly improved by M-AT under appropriate conditions. It was found that the attapulgite modified by hydrochloric acid was similar to polyaluminum ferric silicate chloride (PAFSiC). The high efficiency for M-AT to flocculate Microcystis aeruginosa in freshwater was due to the mechanism of bridging and netting effect. Caenorhabditis elegans was used to detect the toxicity of N-AT and M-AT. The results showed that there was no significant toxicity on this organism. Attapulgite is a natural material, which can be readily available, abundant, and relatively inexpensive. Using modified attapulgite to remove the harmful algal blooms could have the advantages of high effectiveness, low cost, and low impact on the environment.

Nano-networks have better adsorption capability than nano-rods

Abstract Ion beam bombardment, as a unique and facile technique, was found and developed to fabricate nano-networks from rigid nano-rods. To study the differences of their characteristics, attapulgite (ATP) was chosen as a model. The results of methylene blue adsorption performance investigation demonstrated that attapulgite nano-networks (ATP-N) have better adsorption capability than the attapulgite nano-rods (ATP-R). The mechanism proposed that, compared with nano-rods, nano-networks exhibited larger interspace, better separation, higher pore-size and porosity and higher BET specific surface area due to the microstructure of complex three-dimensional networks caused by physical crosslinking, through a series of analysis of the scanning electron microscopy, BET surface area and X-ray powder diffraction.

Harmful algae blooms removal from fresh water with modified vermiculite

Vermiculite and vermiculite modified with hydrochloric acid were investigated to evaluate their flocculation efficiencies in freshwater containing harmful algae blooms (HABs) (Microcystis aeruginosa). Scanning electron microscope, Fourier transform infrared spectroscopy, X-ray diffraction, converted fluorescence microscope, plasma-atomic emission spectrometry, and Zetasizer were used to study the flocculation mechanism of modified vermiculite. It was found that the vermiculite modified with hydrochloric acid could coagulate algae cells through charge neutralization, chemical bridging, and netting effect. The experimental results show that the efficiency of flocculation can be notably improved by modified vermiculite. Ninety-eight per cent of algae cells in algae solution could be removed within 10 min after the addition of modified vermiculite clay. The method that removal of HABs with modified vermiculite is economical with high efficiency, and more research is needed to assess their ecological impacts before using in practical application.

Carbon nanodots-based nanocomposites with enhanced photocatalytic performance and photothermal effects

Carbon nanomaterials with variable bandgaps exhibit wide spectral absorption, and photoluminescent nanodots have attracted much interest. In this work, carbon nanodots (CNDs) are grafted onto the surface of TiO2 nanotubes to enhance the photocatalytic properties. The CNDs increase light absorption, trap and shuttle photo-generated electrons, and enhance the pollutant adsorptivity. In addition, the synergistic photothermal effect of the CNDs-based nanocomposite facilitates photocatalysis. The CNDs-based nanocomposites with improved photothermal performance and efficient photocatalytic characteristics have large potential in environment and energy applications.

Controlling enironmental pollution by application of inartificial nano material

Nano technology and nano material were widely applied to solve the problem of water pollution. It is known that on their way forward, people are bound to run into lakes eutrophication in the world, owing to pollution source not being controlled. Among all pollution sources, agricultual widespread pollution, such as fertilizers nutrient to wash away, and inner pollution in the lake, such total nitrogen and phosphorin, COD and algae, have yet not to find effective controlling their methods. Recent advances in research on application of nano material have opened new areas of study in the field of the lakes eutrophication prevent and treatment, using magnetic or no-magnetic nano materials. Nano materials which were pretreated by modification of chemistry treatments could self-assemble a micro-nano network in aqueous phase. Pollutant micro molecules were banded around the micro-nano network by hydrogen bond, Van Der Waals force and viscous force, to enlaarge their spacial scale comparing with that of water molecule, so that they could easily be separated from water. Fertilizer-lose-control technology has been invented by micro-nano network structure of the nutrient which is blocked by soil filtration. The magnetic separation of water-algae technology was invented by adding magnetic material into mico-nano network materials. Both of these technologies are been engineered and industrialization. The output of controlled releasing fertilizer-lose-control agent reached 2×104 tonnes per year, magnetic flocculating agent was 5000 tonnes per year.