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

Applications of biosynthesized metallic nanoparticles - a review.

Lead and cadmium sorption mechanisms on magnetically modified biochars.

A direct procedure for the determination of total soil carbohydrate content and a classic determination after acid hydrolysis, both employing the phenol-sulphuric acid method, are compared. The direct procedure enables simultaneous determination of mono-, oligo- and polysaccharides without prior hydrolysis. This procedure is reproducible and takes only a short period of time. The correlation between the proposed method and the classic one with hydrolysis was high (r2=0.9843; n=11; p=0.05).

Direct determination of total soil carbohydrate content

Magnetic charcoal was prepared by entrapment of fine charcoal particles into the structure of magnetic iron oxides. This adsorbent can efficiently adsorb a variety of organic compounds. For the adsorption experiments water soluble organic dyes belonging to the triphenylmethane, heteropolycyclic and azodye groups were used as model compounds. Maximum adsorption capacities ranged between 10 and 20 mg of dyes per 1 cm3 of the sedimented adsorbent; this corresponds to 132·5–265 mg of dyes per 1 g of the dried adsorbent. © 1997 SCI.

Adsorption of water-soluble organic dyes on magnetic charcoal

Magnetic composite based on poly(oxy-2,6-dimethyl-1,4-phenylene) (PODMP) was prepared by melting the polymer with e-caprolactam in a presence of fine magnetite particles. Magnetic PODMP was used for sorption of water soluble organic compounds (dyes belonging to triphenylmethane, heteropolycyclic and azo dye groups) from water solutions. There were considerable differences in the binding of the dyes tested. In general, heteropolycyclic dyes exhibited the lowest sorption.

Ivo Šafařík

Papers

Applications of biosynthesized metallic nanoparticles - a review.

Lead and cadmium sorption mechanisms on magnetically modified biochars.

Direct determination of total soil carbohydrate content

Adsorption of water-soluble organic dyes on magnetic charcoal

Sorption of water soluble organic dyes on magnetic poly(oxy-2,6-dimethyl-1,4-phenylene)