Zhengyan Wu

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.

A unique technology to transform inorganic nanorods into nano-networks

An inorganic nano-network of attapulgite is formed from rigid nanorods using ion beam bombardment. The structure of the nano-networks depends on the ion beam fluence for the same ion energy. Scanning electron microscopy reveals that ion beam bombardment improves the dispersion of the attapulgite particles and the change in the shape of the rod-shaped attapulgite particles stems from the thermal stress induced by ion beam bombardment. This phenomenon is more obvious for higher ion fluences. The bent or twisted rod-shaped attapulgite particles cross-link to form a network structure, which is stable in water, and when the ion fluence is increased further, the cross-linked points are permanently sealed. The improved materials are more useful than clava attapulgite particles.

Controlling nitrogen migration through micro-nano networks

Nitrogen fertilizer unabsorbed by crops eventually discharges into the environment through runoff, leaching and volatilization, resulting in three-dimensional (3D) pollution spanning from underground into space. Here we describe an approach for controlling nitrogen loss, developed using loss control fertilizer (LCF) prepared by adding modified natural nanoclay (attapulgite) to traditional fertilizer. In the aqueous phase, LCF self-assembles to form 3D micro/nano networks via hydrogen bonds and other weak interactions, obtaining a higher nitrogen spatial scale so that it is retained by a soil filtering layer. Thus nitrogen loss is reduced and sufficient nutrition for crops is supplied, while the pollution risk of the fertilizer is substantially lowered. As such, self-fabrication of nano-material was used to manipulate the nitrogen spatial scale, which provides a novel and promising approach for the research and control of the migration of other micro-scaled pollutants in environmental medium.

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.