Bioavailability, accumulation and effects of heavy metals in sediments with special reference to United Kingdom estuaries: a review

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

A review of chemical, electrochemical and biological methods for aqueous Cr(VI) reduction

Carbon dioxide is often promoted as a sustainable solvent, as CO 2 is non-flammable, exhibits a relatively low toxicity and is naturally abundant. However, injudicious use of carbon dioxide in a process or product can reduce rather than enhance overall sustainability. This review specifically examines the use of CO 2 to create greener processes and products, with a focus on research and commercialization efforts performed since 1995. The literature reveals that use of CO 2 has permeated almost all facets of the chemical industry and that careful application of CO 2 technology can result in products (and processes) that are cleaner, less expensive and of higher quality.

Supercritical and near-critical CO2 in green chemical synthesis and processing

Soil washing for metal removal: a review of physical/chemical technologies and field applications.

Reduction of hexavalent chromium mediated by micro- and nano-sized mixed metallic particles.

Measurements of solubilities in supercritical CO 2 corroborated the hypothesis that the nonpolar character of a series of tetraalkylammonium dialkyldithiocarbamate ion pairs was influenced (i) primarly by the chain length of the alkyl substituent on the carbamate nitrogen and (ii) to a lesser extent, by the chain length of the alkyl substituent(s) on the ammonium counterion. Similarly, the solubility of Zn-dithiocarbamate complexes decreased in the order dibutyl (DBDTC)>diethyl >pyrrolidine. An extraction protocol in which SC-CO 2 was saturated with tetrabutylammonium DBDTC prior to dynamic complexation/mobilization of 12-20 μg/mL Zn, Cd, or Pb analyte from aqueous solution resulted in >73% and >94% analyte removal within 5 and 15 min extraction, respectively

Recovery of Metals from Aqueous Media by Extraction with Supercritical Carbon Dioxide

Simultaneous mobilization of heavy metals and polychlorinated biphenyl (PCB) compounds from soil with cyclodextrin and EDTA in admixture.

Influence of various organic molecules on the reduction of hexavalent chromium mediated by zero-valent iron.

Hydrogen-saturated water or sodium borohydride were inefficient sources of active hydrogen species for the palladium-alumina accelerated hydrodechlorination (HDC) and subsequent hydrogenolysis of 4-chlorophenol (4-CP) or 2,6-dichlorophenol (2,6-DCP) in water at ambient temperature and pressure. By contrast, hydrogen gas in the presence of Pd 0 /Al 2 O 3 accelerator mediated both hydrodechlorination and partial hydrogenolysis to cyclohexanone. 4-CP or pentachlorophenol (PCP) was converted quantitatively to cyclohexanone in 1 h and subsequently reduced further to cyclohexanol (∼25 mol%) after 3 h. With ammonium formate, HDC of 4-CP was quantitative but hydrogenolysis to cyclohexanol was sluggish (∼14 mol% after 1 h). Whereas zero-valent iron or magnesium generated only traces (∼3 mol%) of phenol, nickel metal powder (Ni 0 ) and Raney-type nickel (Ni–Al) but not NiCl 2 mediated HDC/hydrogenolysis in the presence of NaBH 4 but not H 2 . In these cases, hydrogenolysis, at somewhat elevated temperatures, generated cyclohexanol (14–35 mol%) and no cyclohexanone was observed. At elevated H 2 pressure (414 kPa) and 333 K over Pd 0 /γ-Al 2 O 3 , hydrogenolysis of PCP to cyclohexanone was complete after 30 min. Further increase in pressure (to 4137 kPa) with N 2 seemed to accelerate the reaction rate for shorter reaction times (10 min) but if CO 2 served to increase P, the rates but not the course of reaction were retarded appreciably consistent with competitive inhibition of catalytic sites by CO 2 .

William D. Marshall

Papers

Reduction of hexavalent chromium mediated by micro- and nano-sized mixed metallic particles.

Recovery of Metals from Aqueous Media by Extraction with Supercritical Carbon Dioxide

Simultaneous mobilization of heavy metals and polychlorinated biphenyl (PCB) compounds from soil with cyclodextrin and EDTA in admixture.

Influence of various organic molecules on the reduction of hexavalent chromium mediated by zero-valent iron.

Catalytic hyrodechlorination of chlorophenols in aqueous solution under mild conditions