This article gives an overview of the application of nanomaterials in environmental remediation. In the area of environmental remediation, nanomaterials offer the potential for the efficient removal of pollutants and biological contaminants. Nanomaterials in various shapes/morphologies, such as nanoparticles, tubes, wires, fibres etc., function as adsorbents and catalysts and their composites with polymers are used for the detection and removal of gases (SO2, CO, NOx, etc.), contaminated chemicals (arsenic, iron, manganese, nitrate, heavy metals, etc.), organic pollutants (aliphatic and aromatic hydrocarbons) and biological substances, such as viruses, bacteria, parasites and antibiotics. Nanomaterials show a better performance in environmental remediation than other conventional techniques because of their high surface area (surface-to-volume ratio) and their associated high reactivity. Recent advances in the fabrication of novel nanoscale materials and processes for the treatment of drinking water and industrial waste water contaminated by toxic metal ions, radionuclides, organic and inorganic solutes, bacteria and viruses and the treatment of air are highlighted. In addition, recent advances in the application of polymer nanocomposite materials for the treatment of contaminants and the monitoring of pollutants are also discussed. Furthermore, the research trends and future prospects are briefly discussed.

A review on nanomaterials for environmental remediation

Using pre-established trial sites on allophanic soils, we investigated the impacts of long to medium-term pastoral management practices, such as fertilisation and grazing intensity, on a range of soil biological and biochemical properties; hot water-extractable C (HWC), water-soluble C (WSC), hot-water extractable total carbohydrates, microbial biomass-C and N and mineralisable N These properties were examined for their usefulness as soil quality indicators responding to changes in the rhizosphere caused by management practices Adjacent cropping, market garden and native bush sites located on similar soil types were included to determine the changes in soil biological and biochemical properties resulting from changes in land use The seasonal variability of HWC and its relationship with other labile fractions of soil organic matter was also examined

Microbial biomass-C, mineralisable N and extractable total carbohydrates showed promise in differentiating treatment and land use effects However, HWC was one of the most sensitive and consistent indicators examined at 52 different sites The impact of different land uses on the amounts of HWC in the same soil type was far greater than that was observed for the soil organic carbon The average values of HWC for soil under different land use were: native (4000 μg C g−1 soil), sheep/beef pastures (3400), dairy pastures (3000), cropping (1000) and market gardening soils (850) HWC was also sensitive to differences within an ecosystem, eg effects of grazing intensities and effects of N or P fertilisers on pastures The sheep and beef/cattle grazed pastures always had higher amounts of HWC than the intensively grazed dairy pastures Nitrogen fertiliser application (200 and 400 kg N ha−1 yr−1) over the previous 5 yr had significant (P<0001) negative impacts on HWC and other soil microbial properties In contrast, long-term application of P fertilisers had a significant (P<0001) positive effect on the HWC levels in pastoral soils In the case of long-term P trials, HWC increased even though no increase in the total soil carbon pool was detected

HWC was positively correlated with soil microbial biomass-C (R2=084), microbial nitrogen (R2=072), mineralisable N (R2=086), and total carbohydrates (R2=088) All these correlations were significant at P<0001 level of significance The HWC was also positively correlated with WSC and total organic C However, these correlations were poorer than those found for other soil parameters Most of these measurements have been actively promoted as key indicators of soil quality Given the strong correlations between HWC and other biochemical measurements, HWC could be used as an integrated measure of soil quality When HWC is extracted, other pools of labile nutrients are also extracted along with C Therefore it is suggested that decline in HWC would also indicate a decline in other labile organic pools of nutrients such as nitrogen, sulphur and phosphorus About 40–50% of the C in the HWC extract was present as carbohydrates

Hot-water extractable carbon in soils: a sensitive measurement for determining impacts of fertilisation, grazing and cultivation

A novel magnetic biochar efficiently sorbs organic pollutants and phosphate

Water purification using magnetic assistance: a review.

Use of magnetic techniques for the isolation of cells

Magnetically modified peanut husks were used as an adsorbent of cadmium and lead ions from aqueous solutions. Sorption and desorption experiments were carried out and adsorption isotherm models were calculated to assess the sorption capacity of the material. Langmuir adsorption isotherm was the best fitting model both in one-metal ion and two-metal ions solutions suggesting monolayer adsorption taking place. The observed desorption rate was very low, metals are therefore strongly bound on the surface of the adsorbent. Magnetically modified peanut husks were found to be suitable adsorbent for removal of heavy metal ions from water.

Magnetically modified peanut husks as an effective sorbent of heavy metals

Batch isolation of hen egg white lysozyme with magnetic chitin

Flat magnetic separator was used to separate magnetic bioaffinity adsorbents from litre volumes of suspensions. Both magnetic cross-linked erythrocytes and magnetic chitosan were efficiently separated; at least 95% adsorbent recovery was achieved at maximum flow rate (1680 ml min−1). Using this system low amounts of trypsin were concentrated from large sample volumes using magnetic erythrocytes as affinity adsorbent.

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Large-scale separation of magnetic bioaffinity adsorbents

Magnetite particles bearing covalently immobilized copper phthalocyanine dye ("blue magnetite") were prepared and used for the sorption of triphenylmethane dyes from aqueous solutions. The binding of some triphenylmethane dyes bearing two or three amino groups (basic fuchsin, crystal violet, malachite green) followed the Langmuir adsorption model. The maximum adsorption capacities were calculated. Dyes having no amino group in their molecules exhibited only low adsorption to immobilized copper phthalocyanine. The presence of amino groups in the molecules of triphenylmethane dyes seems to be necessary for their efficient binding on blue magnetite. Generally, efficient sorption of the organic compounds to immobilized copper phthalocyanine may be conditional on a cooperative effect of two parameters, viz. a certain planarity of the sorbate molecule and interaction of the central copper ion of the phthalocyanine molecule with the sorbate amino group or heterocyclic nitrogen atom.

Study of Sorption of Triphenylmethane Dyes on a Magnetic Carrier Bearing an Immobilized Copper Phthalocyanine Dye

Biocompatible materials exhibiting different types of response to external magnetic field have already found many important applications in various areas of biosciences, biotechnology, medicine, environmental technology etc. In most cases they can be described as composite materials, where the magnetic properties are caused by the presence of iron oxides nano- or microparticles. Such materials can be efficiently separated from difficult-to-handle samples and targeted to the desired place, applied as contrast agents for magnetic resonance imaging or used to generate heat during exposure to alternating magnetic field.

Ivo Šafařík

Papers

Magnetically modified peanut husks as an effective sorbent of heavy metals

Batch isolation of hen egg white lysozyme with magnetic chitin

Large-scale separation of magnetic bioaffinity adsorbents

Study of Sorption of Triphenylmethane Dyes on a Magnetic Carrier Bearing an Immobilized Copper Phthalocyanine Dye

Magnetic Nanoparticles for Biomedicine