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Plastic is a material that has become ubiquitous since entering the marketplace in the 1930s and 1940s; as a result, the presence of nano and microplastics (NMPs) are pervasive in natural environments affecting air, soil and water ecosystems. These NMPs are varied in size (categorised as either microplastics at 5 mm–1 µm or nanoplastics at < 1 µm), shape and chemical composition. They represent a potential threat to aquatic life and human health through ingestion and inhalation. The toxicity of NMPs is attributed to chemical additives introduced during production and the absorbance of inorganic and organic chemical contaminants in environmental settings. This review is designed to discuss the use of biochar as a natural adsorbent for the remediation of water contaminated with NMPs. Biochar is a sustainable, affordable material which can remediate water and contribute to ecosystem restoration. Whilst it is well established as a material to sorb organic and inorganic contaminants, its use to remove NMPs is in its infancy and as such this review sets out to outline the mechanisms and modifications of biochar to remove NMPs from aqueous environments. Although removal mechanisms in laboratory settings are becoming clearer this review highlights that remediative studies need to be undertaken in conjunction with the systematic investigation of the effect of key environmental parameters on remediation and the use of environmentally aged NMPs. The future direction of this discipline also needs to incorporate field trials alongside laboratory work to develop a stronger understanding of the viability of biochar to remove NMPs from waterways.

The direct fluorination of intimately mixed niobium and tantalum powders gives a range of mixed‐metal pentafluorides [NbxTa4‐xF20] (x = 1 2, 2 3, 3 4) as discreet species isostructural with tantalum pentafluoride (x = 0 1). The crystal structures of 1–4are indistinguishable by X‐ray crystallography. Complex 1crystallizes in the monoclinic space group C2/m with a = 9.5462(13), b = 14.3578(19), c = 5.0174(7) Å, β = 97.086(2)°, Z = 2. The geometry about the tantalum atom is distorted octahedral with 2 short and 2 slightly longer Ta‐Fterminal, and 2 Ta‐Fbridgingdistances. The angles at the bridging fluorine atoms are 172.9(5)°.

The effects of relative humidity (40–90% RH) and varying glutaraldehyde vapour concentrations (&lt; 0.1 ppm) on the response of an electrochemical fuel cell sensor have been investigated over time (0–400 s). These studies have identified changes in the response of the fuel cell with time after sampling. In particular, it has been found that the maximum cell output for water vapour occurs ca. 10 s after sampling whilst the response to glutaraldehyde occurs much later (> 100 s). For mixtures containing different ratios of water and glutaraldehyde vapours, the time taken to reach maximum fuel cell response varies between 10 and 100 s, depending on the ratio of the two vapours. For instance, glutaraldehyde vapour containing higher % RH has been found to result in shorter times to reach maximum fuel cell response. A comparison was made between measuring glutaraldehyde vapour concentrations in the presence of water vapour at the maximum fuel cell response and also at a fixed interval (240 s) after sampling. Such a comparison resulted in a reduction in the standard error from 36% to 5% for a glutaraldehyde vapour sample (0.023 ppm) measured at different values of relative humidity (40 to 80%). Examination of the effect of the sample volume (30–60 ml) on the response of the fuel cell shows, as expected, an approximate doubling of the fuel cell response. Optimisation of the fuel cell measurement parameters to measure a 60 ml sample leads to a lowering of the limit of detection from 0.083 ppm (for data taken at the maximum cell response) to 0.017 ppm for data measured 240 s after sampling. In the light of recent reductions in the legal limits for exposure to glutaraldehyde, this has important implications for the measurement of glutaraldehyde vapour in the workplace.

High surface area cobalt–iron oxides (with Co ∶ Fe ratios of [3 ∶ 1], [1 ∶ 1] and [1 ∶ 2]) have been prepared by the calcination of predominantly single-phase, coprecipitated hydrotalcite-type precursors prepared from mixed-Co2+–Fe3+ aqueous solutions. The oxide structures were all spinels; for the Co–Fe [3 ∶ 1] oxide, this was a Co₃O₄-type lattice, for the Co–Fe [1 ∶ 2] sample, it was a Fe₃O₄-type lattice and for Co–Fe [1 ∶ 1] an equal mix of the two was observed. The H₂S uptake of all the oxides was tested at 303 K and the data correlated with sorbent preparation and characterisation. The Co–Fe [1 ∶ 1] oxide absorbed the most H₂S before breakthrough and further studies into the preparation of this oxide showed that nitrate-free precursors produced at pH 7 and then aged for 30 minutes or more gave rise to the best oxide sorbents after calcination at 623 K rather than 723 K. These observations have been rationalised on the basis that these oxides had lower density and a greater mix of Co2+/3+ and Fe2+/3+ leading to more distortion of the parent oxide lattice. Increased H₂S uptake was ascribed to more rapid ion diffusion through the sorbent lattice leading to enhanced replenishment of surface oxide.

A series of cobalt–zinc hydroxycarbonate precursors with nominal Co/Zn atomic ratios of 0/100, 10/90, 20/80, 30/70, 40/60, 50/50, 70/30, 90/10 and 100/0 have been synthesized from their mixed metal nitrates and ammonium carbonate by a coprecipitation route. X-Ray and electron diffraction studies of the precursors revealed that hydrozincite, Zn5(CO3)2(OH)6 , was the major phase at Co/Zn ratios≤30/70 and spherocobaltite, CoCO3 , predominated at Co/Zn ratios of 50/50 to 90/10. The Co/Zn 100/0 precursor formed only the metastable basic carbonate Co(CO3)0.5(OH)1.0 0.1H2O. UV–VIS–NIR diffuse reflectance spectroscopy revealed that the cobalt was present in the 2+ oxidation state in an octahedral environment in all the precursors. Decomposition of the Co/Zn precursors at 350 °C resulted in the formation of ZnO as the major phase at low Co loadings and Co3O4 as the major phase at high loadings. The highest surface areas were attained from the decomposition of basic cobalt carbonate or spherocobaltite containing little or no zinc in solid solution. XPS studies of the oxides revealed that only Co3+ and Zn2+ ions were present at the surface at Co/Zn ratios≤30/70 indicating the presence of the ‘surface spinel’, ZnCo2O4 . Co2+ was detected at higher Co loadings.

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